None Hang Wu, None Liao Chen, None Shuai Li, None Yvfan Du, None Chi Zhang, None Xinliang Zhang
Orbital Angular Momentum (OAM) lasers have potential demand in many applications such as large capacity communication systems, laser processing, particle manipulation and quantum optics. OAM mode femtosecond fiber laser has become the research focus with the advantages of simple structure, low cost and high peak power. The current OAM mode femtosecond fiber lasers have made breakthroughs in the repetition frequency, pulse width, spectrum width and other key parameters, but it is difficult to achieve good overall performance. Besides, the repetition rate is currently in tens of MHz. In this paper, a large-bandwidth mode coupler is made based on the mode phase matching principle. Among them, the first order mode coupler with 3dB polarization dependent loss is made by the technology of strong fused biconical taper, and the second order mode coupler with 0.3dB polarization dependent loss is made by the technology of weak fused biconical taper. Combined with the nonlinear polarization rotation mode-locking mechanism, OAM mode femtosecond fiber lasers with over 100 MHZ repetition rate are built. The achievement of the key parameters is attributed to the selection of dispersion shifted fibers that can accurately adjust intracavity dispersion. Compared to traditional dispersion compensation fibers (DCF), the group velocity dispersion is reduced by an order of magnitude, so it can better adjust intracavity dispersion to achieve the indicators of large spectral bandwidth and narrow pulse width. In addition, the diameter of the fiber is 8μm, which is the same as that of a single mode fiber. Compared to DCF, the fusion loss can be ignored, so only a shorter gain Erbium-doped fiber is required that ensure a shorter overall cavity length and achieve high repetition frequency. The experimental results show that the first order OAM mode fiber laser has 113.6 MHz repetition rate, 98 fs half-height full pulse width, and 101nm 10-dB bandwidth. Second-order OAM mode fiber laser has 114.9 MHz repetition rate, 60 fs half-height full pulse width, and 100nm 10-dB bandwidth. Compared with the reported schemes, our scheme has better performance in key parameters such as repetition rate, pulse width and spectral width. We believe that the OAM mode fiber laser with good over performance is expected to be more widely used in OAM communication, particle manipulation and other research fields.
{"title":"Orbital angular momentum mode femtosecond fiber laser with over 100 MHz repetition rate","authors":"None Hang Wu, None Liao Chen, None Shuai Li, None Yvfan Du, None Chi Zhang, None Xinliang Zhang","doi":"10.7498/aps.72.20231085","DOIUrl":"https://doi.org/10.7498/aps.72.20231085","url":null,"abstract":"Orbital Angular Momentum (OAM) lasers have potential demand in many applications such as large capacity communication systems, laser processing, particle manipulation and quantum optics. OAM mode femtosecond fiber laser has become the research focus with the advantages of simple structure, low cost and high peak power. The current OAM mode femtosecond fiber lasers have made breakthroughs in the repetition frequency, pulse width, spectrum width and other key parameters, but it is difficult to achieve good overall performance. Besides, the repetition rate is currently in tens of MHz. In this paper, a large-bandwidth mode coupler is made based on the mode phase matching principle. Among them, the first order mode coupler with 3dB polarization dependent loss is made by the technology of strong fused biconical taper, and the second order mode coupler with 0.3dB polarization dependent loss is made by the technology of weak fused biconical taper. Combined with the nonlinear polarization rotation mode-locking mechanism, OAM mode femtosecond fiber lasers with over 100 MHZ repetition rate are built. The achievement of the key parameters is attributed to the selection of dispersion shifted fibers that can accurately adjust intracavity dispersion. Compared to traditional dispersion compensation fibers (DCF), the group velocity dispersion is reduced by an order of magnitude, so it can better adjust intracavity dispersion to achieve the indicators of large spectral bandwidth and narrow pulse width. In addition, the diameter of the fiber is 8μm, which is the same as that of a single mode fiber. Compared to DCF, the fusion loss can be ignored, so only a shorter gain Erbium-doped fiber is required that ensure a shorter overall cavity length and achieve high repetition frequency. The experimental results show that the first order OAM mode fiber laser has 113.6 MHz repetition rate, 98 fs half-height full pulse width, and 101nm 10-dB bandwidth. Second-order OAM mode fiber laser has 114.9 MHz repetition rate, 60 fs half-height full pulse width, and 100nm 10-dB bandwidth. Compared with the reported schemes, our scheme has better performance in key parameters such as repetition rate, pulse width and spectral width. We believe that the OAM mode fiber laser with good over performance is expected to be more widely used in OAM communication, particle manipulation and other research fields.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136053405","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
None Fan Xiao-Zheng, None Li Yi-Lian, None Wu Yi, None Chen Jun-Cai, None Xu Guo-Liang, None An Yi-Peng
Two-dimensional semiconductor materials with intrinsic magnetism have great application prospects in realizing spintronic devices with low power consumption, small size and high efficiency. Some two-dimensional materials with special lattice structures, such as kagome lattice crystals, are favored by researchers because of their novel properties in magnetism and electronic properties. Recently, a new two-dimensional magnetic semiconductor material Nb3Cl8 monolayer with kagome lattice structure was successfully prepared, which provides a new platform for exploring two-dimensional magnetic semiconductor devices with kagome structure. In this work, we study the electronic structure and magnetic anisotropy of Nb3Cl8 monolayer. We also further construct its p-n junction diode and study its spin transport properties by using density functional theory combined with non-equilibrium Green's function method. The results show that the phonon spectrum of the Nb3Cl8 monolayer has no negative frequency, confirming its dynamic stability. The band gap of the spin-down state (1.157 eV) is significantly larger than that of the spin-up state (0.639 eV). The magnetic moment of the Nb3Cl8 monolayer is 0.997 μB, and its easy magnetization axis is in the plane and along the x axis direction based on its energy of magnetic anisotropy. Nb atoms make the main contribution to the magnetic anisotropy. When the strain is applied, the band gap of the spin-down states will decrease, while the band gap of the spin-up state is monotonously decreased from the negative (compress) to positive (tensile) strain. As the strain variable goes from -6% to 6%, the contribution of Nb atoms to the total magnetic moment gradually increases. Moreover, strain causes the easy magnetization axis of the Nb3Cl8 monolayer to flip vertically from in-plane to out-plane. The designed p-n junction diode nanodevice based on Nb3Cl8 monolayer exhibits an obvious rectification effect. In addition, the current in the spin-up state is larger than that in the spin-down state, exhibiting a spin-polarized transport behavior. Moreover, a negative differential resistance (NDR) phenomenon is also observed, which could be used in the NDR devices. These results demonstrate that the Nb3Cl8 monolayer material has great potential application in the next generation of high-performance spintronic devices, and further experimental verification and exploration of this material and related two-dimensional materials are needed.
{"title":"Magnetic and spin transport properties of a two-dimensional magnetic semiconductor kagome lattice Nb<sub>3</sub>Cl<sub>8</sub> monolayer","authors":"None Fan Xiao-Zheng, None Li Yi-Lian, None Wu Yi, None Chen Jun-Cai, None Xu Guo-Liang, None An Yi-Peng","doi":"10.7498/aps.73.20231163","DOIUrl":"https://doi.org/10.7498/aps.73.20231163","url":null,"abstract":"Two-dimensional semiconductor materials with intrinsic magnetism have great application prospects in realizing spintronic devices with low power consumption, small size and high efficiency. Some two-dimensional materials with special lattice structures, such as kagome lattice crystals, are favored by researchers because of their novel properties in magnetism and electronic properties. Recently, a new two-dimensional magnetic semiconductor material Nb<sub>3</sub>Cl<sub>8</sub> monolayer with kagome lattice structure was successfully prepared, which provides a new platform for exploring two-dimensional magnetic semiconductor devices with kagome structure. In this work, we study the electronic structure and magnetic anisotropy of Nb<sub>3</sub>Cl<sub>8</sub> monolayer. We also further construct its <em>p-n</em> junction diode and study its spin transport properties by using density functional theory combined with non-equilibrium Green's function method. The results show that the phonon spectrum of the Nb<sub>3</sub>Cl<sub>8</sub> monolayer has no negative frequency, confirming its dynamic stability. The band gap of the spin-down state (1.157 eV) is significantly larger than that of the spin-up state (0.639 eV). The magnetic moment of the Nb<sub>3</sub>Cl<sub>8</sub> monolayer is 0.997 μ<sub>B</sub>, and its easy magnetization axis is in the plane and along the <em>x</em> axis direction based on its energy of magnetic anisotropy. Nb atoms make the main contribution to the magnetic anisotropy. When the strain is applied, the band gap of the spin-down states will decrease, while the band gap of the spin-up state is monotonously decreased from the negative (compress) to positive (tensile) strain. As the strain variable goes from -6% to 6%, the contribution of Nb atoms to the total magnetic moment gradually increases. Moreover, strain causes the easy magnetization axis of the Nb<sub>3</sub>Cl<sub>8</sub> monolayer to flip vertically from in-plane to out-plane. The designed <em>p-n</em> junction diode nanodevice based on Nb<sub>3</sub>Cl<sub>8</sub> monolayer exhibits an obvious rectification effect. In addition, the current in the spin-up state is larger than that in the spin-down state, exhibiting a spin-polarized transport behavior. Moreover, a negative differential resistance (NDR) phenomenon is also observed, which could be used in the NDR devices. These results demonstrate that the Nb<sub>3</sub>Cl<sub>8</sub> monolayer material has great potential application in the next generation of high-performance spintronic devices, and further experimental verification and exploration of this material and related two-dimensional materials are needed.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136054185","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
None Cheng Qiu-Zhen, None Huang Yin, None Li Yu-Hui, None Zhang Kai, None Xian Guo-Yu, None Liu He-Yuan, None Che Bing-Yu, None Pan Lu-Lu, None Han Ye-Chao, None Zhu Ke, None Qi Qi, None Xie Yao-Feng, None Pan Jin-Bo, None Chen Hai-Long, None Li Yong-Feng, None Guo Hui, None Yang Hai-Tao, None Gao Hong-Jun
Transition-metal phosphorous chalcogenide MPS (M = transition metal), an emerging type of two-dimensional (2D) van der Waals material with the unique optical and opto-electronic properties, has received much attention. The quasi-one-dimensional chain structure of Nb4P2S21 will possess the strong anisotropic optical and photoelectric properties. Therefore, the single crystal and low-dimensional materials of Nb4P2S21 have potential applications in new polarization controllers, polarization-sensitive photoelectronic detectors, etc. However, there is still a lack of research on the anisotropic optical properties of the high-quality Nb4P2S21 single crystals. Herein, the millimeter-sized Nb4P2S21 single crystals are successfully prepared by the chemical vapor transport method. The chemical composition, the crystal structure and the anisotropic optical properties of the Nb4P2S21 single crystals are carefully analyzed. The energy dispersive X-ray spectroscopy results show that the element distribution is uniform and the element ratio is close to the stoichiometric ratio. The X-ray diffraction and the transmission electron microscopy results show a good crystallinity. The absorption spectra shows that the optical band gap of the Nb4P2S21 single crystal is 1.8 eV. Interestingly, the Nb4P2S21 single crystal can be mechanically exfoliated to obtain few-layer material. The thickness-dependent Raman spectra show that the Raman vibration peaks of bulk and few-layer Nb4P2S21 each have only a weak shift, indicating a weak interlayer interaction in the Nb4P2S21 single crystal. In order to make an in-depth study of the optical properties of Nb4P2S21 single crystals, the polarized-dependent Raman spectra and the femtosecond transient absorption (TA) spectra by using pump pulses and probe pulses with a wavelength of 400 nm and a wavelength range of 500–700 nm are recorded. Importantly, the polarized-dependent Raman scattering spectra with the angle-dependent measurements reveal that the intensity of Raman peak at 202 cm–1 and at 489 cm–1 show a 2-fold symmetry and a 4-fold symmetry in the parallel and vertical polarization configurations, respectively. Moreover, the results of ultrafast carrier dynamics with the in-plane rotation angles of Nb4P2S21 single crystals in the parallel polarization configurations, clearly indicate that both the hot carrier number and the relaxation rate after photoexcitation have the in-plane anisotropic properties. These results are useful in understanding the in-plane anisotropic optical properties of Nb4P2S21 sin
{"title":"In-plane optical anisotropy of quasi-one-dimensional layered semiconductor Nb<sub>4</sub>P<sub>2</sub>S<sub>21</sub> single crystal","authors":"None Cheng Qiu-Zhen, None Huang Yin, None Li Yu-Hui, None Zhang Kai, None Xian Guo-Yu, None Liu He-Yuan, None Che Bing-Yu, None Pan Lu-Lu, None Han Ye-Chao, None Zhu Ke, None Qi Qi, None Xie Yao-Feng, None Pan Jin-Bo, None Chen Hai-Long, None Li Yong-Feng, None Guo Hui, None Yang Hai-Tao, None Gao Hong-Jun","doi":"10.7498/aps.72.20231539","DOIUrl":"https://doi.org/10.7498/aps.72.20231539","url":null,"abstract":"Transition-metal phosphorous chalcogenide <i>M</i>PS (<i>M</i> = transition metal), an emerging type of two-dimensional (2D) van der Waals material with the unique optical and opto-electronic properties, has received much attention. The quasi-one-dimensional chain structure of Nb<sub>4</sub>P<sub>2</sub>S<sub>21</sub> will possess the strong anisotropic optical and photoelectric properties. Therefore, the single crystal and low-dimensional materials of Nb<sub>4</sub>P<sub>2</sub>S<sub>21</sub> have potential applications in new polarization controllers, polarization-sensitive photoelectronic detectors, etc. However, there is still a lack of research on the anisotropic optical properties of the high-quality Nb<sub>4</sub>P<sub>2</sub>S<sub>21</sub> single crystals. Herein, the millimeter-sized Nb<sub>4</sub>P<sub>2</sub>S<sub>21</sub> single crystals are successfully prepared by the chemical vapor transport method. The chemical composition, the crystal structure and the anisotropic optical properties of the Nb<sub>4</sub>P<sub>2</sub>S<sub>21</sub> single crystals are carefully analyzed. The energy dispersive X-ray spectroscopy results show that the element distribution is uniform and the element ratio is close to the stoichiometric ratio. The X-ray diffraction and the transmission electron microscopy results show a good crystallinity. The absorption spectra shows that the optical band gap of the Nb<sub>4</sub>P<sub>2</sub>S<sub>21</sub> single crystal is 1.8 eV. Interestingly, the Nb<sub>4</sub>P<sub>2</sub>S<sub>21</sub> single crystal can be mechanically exfoliated to obtain few-layer material. The thickness-dependent Raman spectra show that the Raman vibration peaks of bulk and few-layer Nb<sub>4</sub>P<sub>2</sub>S<sub>21</sub> each have only a weak shift, indicating a weak interlayer interaction in the Nb<sub>4</sub>P<sub>2</sub>S<sub>21</sub> single crystal. In order to make an in-depth study of the optical properties of Nb<sub>4</sub>P<sub>2</sub>S<sub>21</sub> single crystals, the polarized-dependent Raman spectra and the femtosecond transient absorption (TA) spectra by using pump pulses and probe pulses with a wavelength of 400 nm and a wavelength range of 500–700 nm are recorded. Importantly, the polarized-dependent Raman scattering spectra with the angle-dependent measurements reveal that the intensity of Raman peak at 202 cm<sup>–1</sup> and at 489 cm<sup>–1</sup> show a 2-fold symmetry and a 4-fold symmetry in the parallel and vertical polarization configurations, respectively. Moreover, the results of ultrafast carrier dynamics with the in-plane rotation angles of Nb<sub>4</sub>P<sub>2</sub>S<sub>21</sub> single crystals in the parallel polarization configurations, clearly indicate that both the hot carrier number and the relaxation rate after photoexcitation have the in-plane anisotropic properties. These results are useful in understanding the in-plane anisotropic optical properties of Nb<sub>4</sub>P<sub>2</sub>S<sub>21</sub> sin","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135319624","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
None Hao Bao-Long, None Li Ying-Ying, None Chen Wei, None Hao Guang-Zhou, None Gu Xiang, None Sun Tian-Tian, None Wang Yu-Min, None Dong Jia-Qi, None Yuan Bao-Shan, None Peng Yuan-Kai, None Shi Yue-jiang, None Xie Hua-sheng, None Liu Min-Sheng, None ENN TEAM
Realization of high performance plasma of EXL-50U is very sensitive to NBI (neutral beam injection) heating, and it is expected that the fast ions of NBI are confined well and their energy is transferred to the background plasma by collision moderating. In this paper, the loss of fast ion ripple is simulated based on the equilibrium configuration, fast ion distribution and device waviness data given by the integrated simulation. It is found that the loss fraction of fast ion ripple is about 37%, and the local hot spot is about 0.6 MW/m2, which is unacceptable for the experimental operation of the device. The optimization method includes moving the plasma position and adding FI (ferritic steel plug-in) to reduce the ripple degree, increasing the Ip (plasma current) and optimizing the NBI injection angle. The results show that the ripple distribution must be controlled and the Ip must be increased to more than 600 kA, so that the fast ion loss can be reduced to 3%–4% and the local heat spot can be reduced by an order of magnitude. In this paper, the evaluation methods of fast ion ripple loss in device design are summarized, including the fast ion distribution in phase space, the overlap degree of ripple loss area, and the particle tracking on the time scale of total factor slowing down. The engineering and physical ways to reduce ripple loss are also summarized to provide simulation support for integrated simulation iterative optimization and plant operation.
{"title":"The optimizing numerical simulation of beam ions loss due to toroidal field ripple on EXL-50U spherical torus","authors":"None Hao Bao-Long, None Li Ying-Ying, None Chen Wei, None Hao Guang-Zhou, None Gu Xiang, None Sun Tian-Tian, None Wang Yu-Min, None Dong Jia-Qi, None Yuan Bao-Shan, None Peng Yuan-Kai, None Shi Yue-jiang, None Xie Hua-sheng, None Liu Min-Sheng, None ENN TEAM","doi":"10.7498/aps.72.20230749","DOIUrl":"https://doi.org/10.7498/aps.72.20230749","url":null,"abstract":"Realization of high performance plasma of EXL-50U is very sensitive to NBI (neutral beam injection) heating, and it is expected that the fast ions of NBI are confined well and their energy is transferred to the background plasma by collision moderating. In this paper, the loss of fast ion ripple is simulated based on the equilibrium configuration, fast ion distribution and device waviness data given by the integrated simulation. It is found that the loss fraction of fast ion ripple is about 37%, and the local hot spot is about 0.6 MW/m<sup>2</sup>, which is unacceptable for the experimental operation of the device. The optimization method includes moving the plasma position and adding FI (ferritic steel plug-in) to reduce the ripple degree, increasing the <i>I</i><sub>p</sub> (plasma current) and optimizing the NBI injection angle. The results show that the ripple distribution must be controlled and the <i>I</i><sub>p</sub> must be increased to more than 600 kA, so that the fast ion loss can be reduced to 3%–4% and the local heat spot can be reduced by an order of magnitude. In this paper, the evaluation methods of fast ion ripple loss in device design are summarized, including the fast ion distribution in phase space, the overlap degree of ripple loss area, and the particle tracking on the time scale of total factor slowing down. The engineering and physical ways to reduce ripple loss are also summarized to provide simulation support for integrated simulation iterative optimization and plant operation.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135356168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Molecular motor can effectively convert chemical energy into mechanical energy in living organisms, and its research is currently at the forefront of study in biology and physics . The dynamic process of its guided movement, along with the crucial role they play in intra-cellular material transport, has significantly aroused the interest of many researchers. Theoretical and experimental researches have allowed detailed examinations of the motion attributes of these molecular motors. The Brownian ratchet model important. It provides an illustration of a non-equilibrium system that transforms thermal fluctuation into guided transport by utilizing temporal or spatial asymmetry. The mechanism has been extensively explored and studied across fields including physics, biology and nanotechnology. Investigations into a variety of ratchets and identification of optimum conditions contribute to a deeper understanding of guided Brownian particle transport.Preceding studies on ratchet systems largely concentrated on the rectification motions of diverse types of particles – active, polar and chiral – in asymmetric structures. However, the transport of deformable particles in asymmetric channel has not been examined relatively unexamined. Particles in soft material systems such as cell monolayer, tissue, foam, and emulsion are frequently deformable. The shape deformation of these soft particles significantly affects the system's dynamic behavior. Thus, understanding the guided transport of these deformable particles within a confined structure is crucial.In order to explain this problem more clearlyt, we numerically simulate the guided transportation of active, deformable particles within a two-dimensional, periodic, asymmetric channel. We identify the factors that influence the transport of these particles within a confined structure. The main feature of the deformable particle model is that the particle’s shape is characterized by multiple degree of freedom. For active deformable particles, self-propulsion speed disrupts thermodynamic equilibrium, leading to guided transport in spatially asymmetric condition. Our findings demonstrate that a particle's direction of movement is entirely determined by the channel's asymmetric parameter, and it tends to be attracted towards increased stability. Augmenting particle self-propulsion speed and particle softness can facilitate ratchet transport. When v0[请说明这是什么物理量] is large, the particle’s tensile effect becomes more apparent, and particle softening significantly enhances directed transport. In contrast, an increase in density and rotational diffusion can slow particle rectification. Increased density can obstruct particles, making channel passage more difficult. Elevated rotational diffusion reduces persistence length, challenging particle transition through channels. With constant density, a greater number of particles will also encourage rectification. These research fi
{"title":"Directed Transport of Deformable Self-propulsion Particles in an Asymmetric Periodic Channel","authors":"None Guo Rui-Xue, None Ai Bao-Quan","doi":"10.7498/aps.72.20230825","DOIUrl":"https://doi.org/10.7498/aps.72.20230825","url":null,"abstract":"<sec>Molecular motor can effectively convert chemical energy into mechanical energy in living organisms, and its research is currently at the forefront of study in biology and physics . The dynamic process of its guided movement, along with the crucial role they play in intra-cellular material transport, has significantly aroused the interest of many researchers. Theoretical and experimental researches have allowed detailed examinations of the motion attributes of these molecular motors. The Brownian ratchet model important. It provides an illustration of a non-equilibrium system that transforms thermal fluctuation into guided transport by utilizing temporal or spatial asymmetry. The mechanism has been extensively explored and studied across fields including physics, biology and nanotechnology. Investigations into a variety of ratchets and identification of optimum conditions contribute to a deeper understanding of guided Brownian particle transport.</sec><sec>Preceding studies on ratchet systems largely concentrated on the rectification motions of diverse types of particles – active, polar and chiral – in asymmetric structures. However, the transport of deformable particles in asymmetric channel has not been examined relatively unexamined. Particles in soft material systems such as cell monolayer, tissue, foam, and emulsion are frequently deformable. The shape deformation of these soft particles significantly affects the system's dynamic behavior. Thus, understanding the guided transport of these deformable particles within a confined structure is crucial.</sec><sec>In order to explain this problem more clearlyt, we numerically simulate the guided transportation of active, deformable particles within a two-dimensional, periodic, asymmetric channel. We identify the factors that influence the transport of these particles within a confined structure. The main feature of the deformable particle model is that the particle’s shape is characterized by multiple degree of freedom. For active deformable particles, self-propulsion speed disrupts thermodynamic equilibrium, leading to guided transport in spatially asymmetric condition. Our findings demonstrate that a particle's direction of movement is entirely determined by the channel's asymmetric parameter, and it tends to be attracted towards increased stability. Augmenting particle self-propulsion speed and particle softness can facilitate ratchet transport. When <i>v</i><sub>0</sub>[请说明这是什么物理量] is large, the particle’s tensile effect becomes more apparent, and particle softening significantly enhances directed transport. In contrast, an increase in density and rotational diffusion can slow particle rectification. Increased density can obstruct particles, making channel passage more difficult. Elevated rotational diffusion reduces persistence length, challenging particle transition through channels. With constant density, a greater number of particles will also encourage rectification. These research fi","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135400177","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
As a common phenomenon in nature, phase transition has caught people’s attention for a long time. Thus, it has been applied to various fields, such as refrigeration, information and energy storage, and negative thermal expansion. With the virtues of environmental friendliness, high efficiency, noiselessness and easy miniaturization, solid refrigeration technique based on magnetocaloric, electrocaloric, and mechanocaloric effects, is a promising candidate to replace vapor compression technique. Among them, magnetocaloric effect has the longest research history. However, the shortcomings of magnetocaloric effect driven by a single magnetic field limit its solid-state refrigeration application, such as insufficient amplitude of caloric effect, large hysteresis loss, and narrow refrigeration temperature span. To solve these problems, multifield tuning and multicaloric effect came into people's sight. This review introduces our recent research on improving the caloric effect by applying multifield, such as boosting the entropy change, enlarging the transition temperature span, tuning the transition temperature, and lowering the hysteresis losses. Meanwhile, the thermodynamics of multifield and coupled-caloric effect is presented. On the other hand, abnormal thermal expansion (zero thermal expansion, negative thermal expansion) materials have important applications in precision manufacturing. The phase transition and lattice effect dominated by magnetic atoms in the giant magnetocaloric materials with strong magnetic-crystal coupling provide an ideal platform for exploring abnormal thermal expansion. This review also introduces our recent research on abnormal thermal expansion in magnetocaloric materials and prospects relevant research in future.
{"title":"Phase transition regulation, magnetocaloric effect, and abnormal thermal expansion","authors":"None Yuan Lin, None Fengxia Hu, None Baogen Shen","doi":"10.7498/aps.72.20231118","DOIUrl":"https://doi.org/10.7498/aps.72.20231118","url":null,"abstract":"As a common phenomenon in nature, phase transition has caught people’s attention for a long time. Thus, it has been applied to various fields, such as refrigeration, information and energy storage, and negative thermal expansion. With the virtues of environmental friendliness, high efficiency, noiselessness and easy miniaturization, solid refrigeration technique based on magnetocaloric, electrocaloric, and mechanocaloric effects, is a promising candidate to replace vapor compression technique. Among them, magnetocaloric effect has the longest research history. However, the shortcomings of magnetocaloric effect driven by a single magnetic field limit its solid-state refrigeration application, such as insufficient amplitude of caloric effect, large hysteresis loss, and narrow refrigeration temperature span. To solve these problems, multifield tuning and multicaloric effect came into people's sight. This review introduces our recent research on improving the caloric effect by applying multifield, such as boosting the entropy change, enlarging the transition temperature span, tuning the transition temperature, and lowering the hysteresis losses. Meanwhile, the thermodynamics of multifield and coupled-caloric effect is presented. On the other hand, abnormal thermal expansion (zero thermal expansion, negative thermal expansion) materials have important applications in precision manufacturing. The phase transition and lattice effect dominated by magnetic atoms in the giant magnetocaloric materials with strong magnetic-crystal coupling provide an ideal platform for exploring abnormal thermal expansion. This review also introduces our recent research on abnormal thermal expansion in magnetocaloric materials and prospects relevant research in future.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135401846","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
None Li Yao-Long, None Li Zhe, None Li Song-Yuan, None Zhang Ren-Liang
The interlayer bonding of graphene is a modification method of graphene, which can change the mechanical and conductivity of graphene, but also affect its thermal properties. In this paper, the non-equilibrium molecular dynamics method is used to study the thermal conductivity of bilayer graphene nanoribbon which is local carbon sp3 hybridization (covalent bond formed between layers) under different concentration and angle of interlayer Covalent bond chain and different tensile strain. The mechanism of the change of the thermal conductivity of bilayer graphene nanoribbon is analyzed through the density of phonon states. The results are as follows. The thermal conductivity of bilayer graphene nanoribbon decreases with the increase of the interlayer covalent bond concentration due to the intensification of phonon scattering and the reduction of phonon group velocities and effective phonon mean free path. Moreover, the decrease rate of thermal conductivity depends on the distribution angle of covalent bond chain. With the increase of interlayer covalent bond concentration, when the interlayer covalent bond chain is parallel to the direction of heat flow, the thermal conductivity decreases the slowest because the heat transfer channel along the heat flow direction is gradually affected; when the interlayer covalent bond chain is at an angle to the direction of heat flow, the thermal conductivity decreases more rapidly, and the larger the angle, the faster the thermal conductivity decreases. The rapid decline of thermal conductivity is due to the formation of interfacial thermal resistance at the interlayer covalent bond chain, where strong phonon-interface scattering occurs. In addition, it is found that the thermal conductivity of bilayer graphene nanoribbon with interlayer bonding will be further reduced by tensile strain due to the intensification of phonon scattering and the reduction of phonon group velocities. The results show that the thermal conductivity of bilayer graphene nanoribbon can be controlled by interlayer bonding and tensile strain. These conclusions are of great significance for the design and thermal control of graphene based nanodevices.
{"title":"Regulation of thermal conductivity of bilayer graphene nanoribbon through interlayer covalent bond and tensile strain","authors":"None Li Yao-Long, None Li Zhe, None Li Song-Yuan, None Zhang Ren-Liang","doi":"10.7498/aps.72.20231230","DOIUrl":"https://doi.org/10.7498/aps.72.20231230","url":null,"abstract":"The interlayer bonding of graphene is a modification method of graphene, which can change the mechanical and conductivity of graphene, but also affect its thermal properties. In this paper, the non-equilibrium molecular dynamics method is used to study the thermal conductivity of bilayer graphene nanoribbon which is local carbon sp<sup>3</sup> hybridization (covalent bond formed between layers) under different concentration and angle of interlayer Covalent bond chain and different tensile strain. The mechanism of the change of the thermal conductivity of bilayer graphene nanoribbon is analyzed through the density of phonon states. The results are as follows. The thermal conductivity of bilayer graphene nanoribbon decreases with the increase of the interlayer covalent bond concentration due to the intensification of phonon scattering and the reduction of phonon group velocities and effective phonon mean free path. Moreover, the decrease rate of thermal conductivity depends on the distribution angle of covalent bond chain. With the increase of interlayer covalent bond concentration, when the interlayer covalent bond chain is parallel to the direction of heat flow, the thermal conductivity decreases the slowest because the heat transfer channel along the heat flow direction is gradually affected; when the interlayer covalent bond chain is at an angle to the direction of heat flow, the thermal conductivity decreases more rapidly, and the larger the angle, the faster the thermal conductivity decreases. The rapid decline of thermal conductivity is due to the formation of interfacial thermal resistance at the interlayer covalent bond chain, where strong phonon-interface scattering occurs. In addition, it is found that the thermal conductivity of bilayer graphene nanoribbon with interlayer bonding will be further reduced by tensile strain due to the intensification of phonon scattering and the reduction of phonon group velocities. The results show that the thermal conductivity of bilayer graphene nanoribbon can be controlled by interlayer bonding and tensile strain. These conclusions are of great significance for the design and thermal control of graphene based nanodevices.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135595467","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Does thermodynamics still hold true for mecroscopic small systems with only limited degrees of freedom? Do concepts such as temperature, entropy, work done, heat transfer, isothermal processes, and the Carnot cycle remain valid? Does the thermodynamic theory for small systems need modifying or supplementing compared with traditional thermodynamics applicable to macroscopic systems? Taking a single-particle system for example, we investigate the applicability of thermodynamic concepts and laws in small systems. We have found that thermodynamic laws still hold true in small systems at an ensemble-averaged level. After considering the information erasure of the Maxwell's demon, the second law of thermodynamics is not violated. Additionally, 'small systems' bring some new features. Fluctuations in thermodynamic quantities become prominent. In any process far from equilibrium, the distribution functions of thermodynamic quantities satisfy certain rigorously established identities. These identities are known as fluctuation theorems. The second law of thermodynamics can be derived from them. Therefore, fluctuation theorems can be considered an upgradation to the second law of thermodynamics. They enable physicists to obtain equilibrium properties (e.g. free energy difference) by measuring physical quantities associated with non-equilibrium processes (e.g. work distributions). Furthermore, despite some distinct quantum features, the performance of quantum heat engine does not outperform that of classical heat engine. The introduction of motion equations into small system makes the relationship between thermodynamics and mechanics closer than before. Physicists can study energy dissipation in non-equilibrium process and optimize the power and efficiency of heat engine from the first principle. These findings enrich the content of thermodynamic theory and provide new ideas for establishing a general framework for non-equilibrium thermodynamics.
{"title":"Theoretical and experimental progress of mesoscopic statistical thermodynamics","authors":"Hai-Tao Quan, Hui Dong, Chang-Pu Sun","doi":"10.7498/aps.72.20231608","DOIUrl":"https://doi.org/10.7498/aps.72.20231608","url":null,"abstract":"Does thermodynamics still hold true for mecroscopic small systems with only limited degrees of freedom? Do concepts such as temperature, entropy, work done, heat transfer, isothermal processes, and the Carnot cycle remain valid? Does the thermodynamic theory for small systems need modifying or supplementing compared with traditional thermodynamics applicable to macroscopic systems? Taking a single-particle system for example, we investigate the applicability of thermodynamic concepts and laws in small systems. We have found that thermodynamic laws still hold true in small systems at an ensemble-averaged level. After considering the information erasure of the Maxwell's demon, the second law of thermodynamics is not violated. Additionally, 'small systems' bring some new features. Fluctuations in thermodynamic quantities become prominent. In any process far from equilibrium, the distribution functions of thermodynamic quantities satisfy certain rigorously established identities. These identities are known as fluctuation theorems. The second law of thermodynamics can be derived from them. Therefore, fluctuation theorems can be considered an upgradation to the second law of thermodynamics. They enable physicists to obtain equilibrium properties (e.g. free energy difference) by measuring physical quantities associated with non-equilibrium processes (e.g. work distributions). Furthermore, despite some distinct quantum features, the performance of quantum heat engine does not outperform that of classical heat engine. The introduction of motion equations into small system makes the relationship between thermodynamics and mechanics closer than before. Physicists can study energy dissipation in non-equilibrium process and optimize the power and efficiency of heat engine from the first principle. These findings enrich the content of thermodynamic theory and provide new ideas for establishing a general framework for non-equilibrium thermodynamics.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135703833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this work, the formation energy, band structure, state density, differential charge density and optoelectronic properties of undoped and Si doped β-Ga2O3 are calculated using GGA+U method based on density functional theory. The results show that the Si-substituted tetrahedron Ga(1) is more easily synthesized in experiments, and the obtained β-Ga2O3 band gap and Ga 3d state peak are in good agreement with the experimental results, and the effective doping is more likely to be obtained under oxygen-poor conditions. After Si doping, the total energy band moves to the low-energy end, and Fermi level enters the conduction band, showing n-type conductive characterastic. Si 3s orbital electrons occupy the bottom of the conduction band, the degree of electronic coocupy is strengthened, and the conductivity is improved. The dielectric function ε2(ω) results show that with the increase of Si doping concentration, the ability to stimulate conductive electrons first increases and then decreases, which is in good agreement with the quantitative analysis results of conductivity. The optical band gap increases and the absorption band edge rises slowly with the increase of Si doping concentration. The results of absorption spectra show that Si-doped β-Ga2O3 has strong deep ultraviolet photoelectric detection ability. The calculated results provide a theoretical reference for the further experimental investigation and the optimization innovation of Si-doped β-Ga2O3 and relative device design.
{"title":"Invesigation of the electronic structure and Optoelectronic properties of Si-doped <i>β</i>-Ga<sub>2</sub>O<sub>3</sub> using GGA+U method based on first-principle","authors":"None Zhang Ying-Nan, None Zhang Min, None Zhang Pai, None Hu Wen-Bo","doi":"10.7498/aps.72.20231147","DOIUrl":"https://doi.org/10.7498/aps.72.20231147","url":null,"abstract":"In this work, the formation energy, band structure, state density, differential charge density and optoelectronic properties of undoped and Si doped <i>β</i>-Ga<sub>2</sub>O<sub>3</sub> are calculated using GGA+U method based on density functional theory. The results show that the Si-substituted tetrahedron Ga(1) is more easily synthesized in experiments, and the obtained <i>β</i>-Ga<sub>2</sub>O<sub>3</sub> band gap and Ga 3d state peak are in good agreement with the experimental results, and the effective doping is more likely to be obtained under oxygen-poor conditions. After Si doping, the total energy band moves to the low-energy end, and Fermi level enters the conduction band, showing n-type conductive characterastic. Si 3s orbital electrons occupy the bottom of the conduction band, the degree of electronic coocupy is strengthened, and the conductivity is improved. The dielectric function ε2(ω) results show that with the increase of Si doping concentration, the ability to stimulate conductive electrons first increases and then decreases, which is in good agreement with the quantitative analysis results of conductivity. The optical band gap increases and the absorption band edge rises slowly with the increase of Si doping concentration. The results of absorption spectra show that Si-doped <i>β</i>-Ga<sub>2</sub>O<sub>3</sub> has strong deep ultraviolet photoelectric detection ability. The calculated results provide a theoretical reference for the further experimental investigation and the optimization innovation of Si-doped <i>β</i>-Ga<sub>2</sub>O<sub>3</sub> and relative device design.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136053389","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
None Xu Jing-Han, None Wu Guo-Jun, None Dong Jing, None Yu Yang, None Feng Fei, None Liu Bo
The random scattering event of light by water medium is the primary reason for the degradation in underwater imaging. Underwater polarization imaging technology can enhance the signal-to-noise ratio of imaging effectively by utilizing the polarization information difference between background scattered light and target light. However, as scattering events increase in the water body, it is difficult to maintain the polarization characteristics of light, which reduces the effect of removing scattering based on polarization characteristics. In addition, the polarization rules of background scattered light in water is unclear, and there is a lack of quantitative description of the polarization characteristics of scattered light. Therefore, researching the polarization transmission characteristics of underwater scattered light is of great significance for the de-scattering work of underwater polarization imaging.In order to clarify the polarization characteristics of underwater background scattered light, especially the polarization angle information, this paper proposes a method for ascertaining polarization angle of background light based on modified polarization difference imaging method. In this method, the coupling relationship between optimal weight coefficient and enhancement measure evaluation (EME) value of the Stokes vector difference result is analyzed, and the background light polarization angle is calculated based on the optimal weight coefficient. Combined with the experiments, the EME distribution trend of the optimal weight coefficient and the modified polarization difference imaging method results in different turbidity water bodies were determined, the scattering suppression limit was explored, and the trend of background scattered light polarization direction with turbidity of water was analyzed. The results show that the proposed method can obtain the exact polarization angle of background scattered light in different water environments, revealing a trend where the polarization direction of background scattered light becomes orthogonal to the incident light direction as the turbidity of the water increases. This research provides a methodological basis for determining the polarization direction of the background scattered light in underwater imaging.
{"title":"Research on polarization characteristics of background light based on modified polarization difference imaging method","authors":"None Xu Jing-Han, None Wu Guo-Jun, None Dong Jing, None Yu Yang, None Feng Fei, None Liu Bo","doi":"10.7498/aps.72.20230639","DOIUrl":"https://doi.org/10.7498/aps.72.20230639","url":null,"abstract":"The random scattering event of light by water medium is the primary reason for the degradation in underwater imaging. Underwater polarization imaging technology can enhance the signal-to-noise ratio of imaging effectively by utilizing the polarization information difference between background scattered light and target light. However, as scattering events increase in the water body, it is difficult to maintain the polarization characteristics of light, which reduces the effect of removing scattering based on polarization characteristics. In addition, the polarization rules of background scattered light in water is unclear, and there is a lack of quantitative description of the polarization characteristics of scattered light. Therefore, researching the polarization transmission characteristics of underwater scattered light is of great significance for the de-scattering work of underwater polarization imaging.In order to clarify the polarization characteristics of underwater background scattered light, especially the polarization angle information, this paper proposes a method for ascertaining polarization angle of background light based on modified polarization difference imaging method. In this method, the coupling relationship between optimal weight coefficient and enhancement measure evaluation (EME) value of the Stokes vector difference result is analyzed, and the background light polarization angle is calculated based on the optimal weight coefficient. Combined with the experiments, the EME distribution trend of the optimal weight coefficient and the modified polarization difference imaging method results in different turbidity water bodies were determined, the scattering suppression limit was explored, and the trend of background scattered light polarization direction with turbidity of water was analyzed. The results show that the proposed method can obtain the exact polarization angle of background scattered light in different water environments, revealing a trend where the polarization direction of background scattered light becomes orthogonal to the incident light direction as the turbidity of the water increases. This research provides a methodological basis for determining the polarization direction of the background scattered light in underwater imaging.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136202171","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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