Understanding the doping evolution from a Mott insulator to a superconductor probably holds the key to resolve the mystery of unconventional superconductivity in copper oxides. To elucidate the evolution of the electronic state starting from the Mott insulator, we dose the surface of the parent phase Ca2CuO2Cl2 by depositing Rb atoms, which are supposed to donate electrons to the CuO2 planes underneath. We successfully achieved the Rb sub-monolayer thin films in forming the square lattice. The scanning tunneling microscopy or spectroscopy measurements on the surface show that the Fermi energy is pinned within the Mott gap but close to the edge of the charge transfer band. In addition, an in-gap state appears at the bottom of the upper Hubbard band (UHB), and the Mott gap will be significantly diminished. Combined with the Cl defect and the Rb adatom/cluster results, the electron doping is likely to increase the spectra weight of the UHB for the double occupancy. Our results provide information to understand the electron doping to the parent compound of cuprates.
{"title":"Mott gap filling by doping electrons through depositing one sub-monolayer thin film of Rb on Ca2CuO2Cl2","authors":"Han Li, Zhaohui Wang, Shengtai Fan, Huazhou Li, Huan Yang, Hai-Hu Wen","doi":"10.1088/0256-307x/41/5/057402","DOIUrl":"https://doi.org/10.1088/0256-307x/41/5/057402","url":null,"abstract":"\u0000 Understanding the doping evolution from a Mott insulator to a superconductor probably holds the key to resolve the mystery of unconventional superconductivity in copper oxides. To elucidate the evolution of the electronic state starting from the Mott insulator, we dose the surface of the parent phase Ca2CuO2Cl2 by depositing Rb atoms, which are supposed to donate electrons to the CuO2 planes underneath. We successfully achieved the Rb sub-monolayer thin films in forming the square lattice. The scanning tunneling microscopy or spectroscopy measurements on the surface show that the Fermi energy is pinned within the Mott gap but close to the edge of the charge transfer band. In addition, an in-gap state appears at the bottom of the upper Hubbard band (UHB), and the Mott gap will be significantly diminished. Combined with the Cl defect and the Rb adatom/cluster results, the electron doping is likely to increase the spectra weight of the UHB for the double occupancy. Our results provide information to understand the electron doping to the parent compound of cuprates.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140728118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-03DOI: 10.1088/0256-307x/41/5/057301
Bowen Zheng, Tao Chen, Hairui Sun, Manman Yang, Bingchao Yang, Xin Chen, Yongsheng Zhang, Xiaobing Liu
As a sister compound of PbTe, SnTe possesses the environmentally friendly elements. However, the pristine SnTe compounds suffer from the high carrier concentration, the large valence band offset between the L and ∑ positions and high thermal conductivity. Using high pressure and high temperature technology, we have synthesized the pristine SnTe samples at different pressure and systemically investigated their thermoelectric properties. High pressure introduced rich microstructures, including the high density dislocations and lattice distortions, which served as the strong phonon scattering centers, thereby reducing the lattice thermal conductivity. For the electrical properties, pressure reduced the harmful high carrier concentration, due to the depression of Sn vacancies. Moreover, pressure induced the valence band convergence, reducing the energy separation between the L and ∑ positions. The band convergence and suppressed carrier concentration increased the Seebeck coefficient. Thus, the power factors of pressure-sintered compounds did not deteriorate significantly under the condition of electrical conductivity decreases. Ultimately, for a pristine SnTe compound synthesized at 5 GPa, a higher ZT value of 0.51 was achieved at 750 K, representing an 140% improvement compared to the value of 0.21 obtained using SPS. Therefore, the high-pressure and high-temperature technology has been demonstrated as an effectively approach to optimize thermoelectric performance.
{"title":"The influence of high pressure induced lattice dislocations and distortions on the thermoelectric performance of pristine SnTe","authors":"Bowen Zheng, Tao Chen, Hairui Sun, Manman Yang, Bingchao Yang, Xin Chen, Yongsheng Zhang, Xiaobing Liu","doi":"10.1088/0256-307x/41/5/057301","DOIUrl":"https://doi.org/10.1088/0256-307x/41/5/057301","url":null,"abstract":"\u0000 As a sister compound of PbTe, SnTe possesses the environmentally friendly elements. However, the pristine SnTe compounds suffer from the high carrier concentration, the large valence band offset between the L and ∑ positions and high thermal conductivity. Using high pressure and high temperature technology, we have synthesized the pristine SnTe samples at different pressure and systemically investigated their thermoelectric properties. High pressure introduced rich microstructures, including the high density dislocations and lattice distortions, which served as the strong phonon scattering centers, thereby reducing the lattice thermal conductivity. For the electrical properties, pressure reduced the harmful high carrier concentration, due to the depression of Sn vacancies. Moreover, pressure induced the valence band convergence, reducing the energy separation between the L and ∑ positions. The band convergence and suppressed carrier concentration increased the Seebeck coefficient. Thus, the power factors of pressure-sintered compounds did not deteriorate significantly under the condition of electrical conductivity decreases. Ultimately, for a pristine SnTe compound synthesized at 5 GPa, a higher ZT value of 0.51 was achieved at 750 K, representing an 140% improvement compared to the value of 0.21 obtained using SPS. Therefore, the high-pressure and high-temperature technology has been demonstrated as an effectively approach to optimize thermoelectric performance.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140747960","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-03DOI: 10.1088/0256-307X/41/4/044205
Tiantian Zhang, Wenpeng Zhou, Zhixiang Li, Yutao Tang, Fan Xu, Haodong Wu, Han Zhang, Jiangshan Tang, Ya-Ping Ruan, Keyu Xia
Nonreciprocal optical devices are essential for laser protection, modern optical communication and quantum information processing by enforcing one-way light propagation. The conventional Faraday magneto-optical nonreciprocal devices rely on a strong magnetic field, which is provided by a permanent magnet. As a result, the isolation direction of such devices is fixed and severely restrict their applications in quantum networks. In this work, we experimentally demonstrate the simultaneous one-way transmission and unidirectional reflection by using a magneto-optical Fabry-Pérot cavity and a magnetic field strength of 50 mT. An optical isolator and a three-port quasi-circulator are realized based on this nonreciprocal cavity system. The isolator achieves an isolation ratio of up to 22 dB and an averaged insertion loss down to 0.97 dB. The quasi-circulator is realized with a fidelity exceeding 99% and an overall survival probability of 89.9%, corresponding to an insertion loss of ~0.46 dB. The magnetic field is provided by an electromagnetic coil, thereby allowing for reversing the light circulating path. The reversible quasi-circulator paves the way for building reconfigurable quantum networks.
{"title":"Reversible optical isolators and quasi-circulators using a magneto-optical Fabry-Pérot cavity","authors":"Tiantian Zhang, Wenpeng Zhou, Zhixiang Li, Yutao Tang, Fan Xu, Haodong Wu, Han Zhang, Jiangshan Tang, Ya-Ping Ruan, Keyu Xia","doi":"10.1088/0256-307X/41/4/044205","DOIUrl":"https://doi.org/10.1088/0256-307X/41/4/044205","url":null,"abstract":"\u0000 Nonreciprocal optical devices are essential for laser protection, modern optical communication and quantum information processing by enforcing one-way light propagation. The conventional Faraday magneto-optical nonreciprocal devices rely on a strong magnetic field, which is provided by a permanent magnet. As a result, the isolation direction of such devices is fixed and severely restrict their applications in quantum networks. In this work, we experimentally demonstrate the simultaneous one-way transmission and unidirectional reflection by using a magneto-optical Fabry-Pérot cavity and a magnetic field strength of 50 mT. An optical isolator and a three-port quasi-circulator are realized based on this nonreciprocal cavity system. The isolator achieves an isolation ratio of up to 22 dB and an averaged insertion loss down to 0.97 dB. The quasi-circulator is realized with a fidelity exceeding 99% and an overall survival probability of 89.9%, corresponding to an insertion loss of ~0.46 dB. The magnetic field is provided by an electromagnetic coil, thereby allowing for reversing the light circulating path. The reversible quasi-circulator paves the way for building reconfigurable quantum networks.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140749415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Here we report on soft $c$-axis point-contact Andreev reflection (PCAR) spectroscopy combining with resistivity measurements on BaFe$_2$(As$_{0.7}$P$_{0.3}$)$_2$, to elucidate the superconducting gap structure in the vicinity of the QCP. A double-peak at the gap edge plus a dip feature at zero-bias has been observed on the PCAR spectra, indicative of the presence of a nodeless gap in BaFe$_2$(As$_{0.7}$P$_{0.3}$)$_2$. Detailed analysis within a sophisticated theoretical model reveal an anisotropic gap with deep gap minima. The PCARs also feature additional structures related to the electron-bosonic coupling mode. Using the extracted superconducting energy gap value, a characteristic bosonic energy $Omega_{b}$ and its temperature dependence are obtained, comparable with the spin-resonance energy observed in neutron scattering experiment. These results indicate a magnetism-driven quantum critical point in BaFe$_2$(As$_{1-x}$P$_x$)$_2$ system.
{"title":"Anisotropic $s$-wave gap in the vicinity of a quantum critical point in superconducting BaFe$_{2}$(As$_{1-x}$P$_{x}$)$_2$ single crystals: a study of point-contact spectroscopy","authors":"Hong-xing Zhan, Yu-chi Lin, Yu-qing Zhao, Hai-yan Zuo, Xing-yu Wang, Xiao-yan Ma, Chun-hong Li, Hui-qian Luo, Gen-fu Chen, Shi-liang Li, Cong Ren","doi":"10.1088/0256-307x/41/4/047402","DOIUrl":"https://doi.org/10.1088/0256-307x/41/4/047402","url":null,"abstract":"\u0000 Here we report on soft $c$-axis point-contact Andreev reflection (PCAR) spectroscopy combining with resistivity measurements on BaFe$_2$(As$_{0.7}$P$_{0.3}$)$_2$, to elucidate the superconducting gap structure in the vicinity of the QCP. A double-peak at the gap edge plus a dip feature at zero-bias has been observed on the PCAR spectra, indicative of the presence of a nodeless gap in BaFe$_2$(As$_{0.7}$P$_{0.3}$)$_2$. Detailed analysis within a sophisticated theoretical model reveal an anisotropic gap with deep gap minima. The PCARs also feature additional structures related to the electron-bosonic coupling mode. Using the extracted superconducting energy gap value, a characteristic bosonic energy $Omega_{b}$ and its temperature dependence are obtained, comparable with the spin-resonance energy observed in neutron scattering experiment. These results indicate a magnetism-driven quantum critical point in BaFe$_2$(As$_{1-x}$P$_x$)$_2$ system.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140755006","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-01DOI: 10.1088/0256-307x/41/4/047103
Hai-Yang Ma, Jia-Xin Yin, M. Zahid Hasan, Jianpeng Liu
We theoretically study the charge order and orbital magnetic properties of a new type of antiferromagnetic kagome metal FeGe. Based on first-principles density functional theory calculations, we study the electronic structures, Fermi-surface quantum fluctuations, as well as phonon properties of the antiferromagnetic kagome metal FeGe. It is found that charge density wave emerges in such a system due to a subtle cooperation between electron–electron interactions and electron–phonon couplings, which gives rise to an unusual scenario of interaction-triggered phonon instabilities, and eventually yields a charge density wave (CDW) state. We further show that, in the CDW phase, the ground-state current density distribution exhibits an intriguing star-of-David pattern, leading to flux density modulation. The orbital fluxes (or current loops) in this system emerge as a result of the subtle interplay between magnetism, lattice geometries, charge order, and spin-orbit coupling (SOC), which can be described by a simple, yet universal, tight-binding theory including a Kane–Mele-type SOC term and a magnetic exchange interaction. We further study the origin of the peculiar step-edge states in FeGe, which sheds light on the topological properties and correlation effects in this new type of kagome antiferromagnetic material.
{"title":"Theory for Charge Density Wave and Orbital-Flux State in Antiferromagnetic Kagome Metal FeGe","authors":"Hai-Yang Ma, Jia-Xin Yin, M. Zahid Hasan, Jianpeng Liu","doi":"10.1088/0256-307x/41/4/047103","DOIUrl":"https://doi.org/10.1088/0256-307x/41/4/047103","url":null,"abstract":"We theoretically study the charge order and orbital magnetic properties of a new type of antiferromagnetic kagome metal FeGe. Based on first-principles density functional theory calculations, we study the electronic structures, Fermi-surface quantum fluctuations, as well as phonon properties of the antiferromagnetic kagome metal FeGe. It is found that charge density wave emerges in such a system due to a subtle cooperation between electron–electron interactions and electron–phonon couplings, which gives rise to an unusual scenario of interaction-triggered phonon instabilities, and eventually yields a charge density wave (CDW) state. We further show that, in the CDW phase, the ground-state current density distribution exhibits an intriguing star-of-David pattern, leading to flux density modulation. The orbital fluxes (or current loops) in this system emerge as a result of the subtle interplay between magnetism, lattice geometries, charge order, and spin-orbit coupling (SOC), which can be described by a simple, yet universal, tight-binding theory including a Kane–Mele-type SOC term and a magnetic exchange interaction. We further study the origin of the peculiar step-edge states in FeGe, which sheds light on the topological properties and correlation effects in this new type of kagome antiferromagnetic material.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140615689","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-01DOI: 10.1088/0256-307x/41/3/031202
Jing Wu, Shanshan Cao, Feng Li
Jet quenching parameter q^ is essential for characterizing the interaction strength between jet partons and nuclear matter. Based on the quark-meson model, we develop a new framework for calculating q^ at finite chemical potentials, in which q^ is related to the spectral function of the chiral order parameter. A mean field perturbative calculation up to the one-loop order indicates that the momentum broadening of jets is enhanced at both high temperature and high chemical potential, and approximately proportional to the parton number density in the partonic phase. We further investigate the behavior of q^ in the vicinity of the critical endpoint (CEP) by coupling our calculation with a recently developed equation of state that includes a CEP in the universality class of the Ising model, from which we discover the partonic critical opalescence, i.e., the divergence of scattering rate of jets and their momentum broadening at the CEP, contributed by scatterings via the σ exchange process. Hence, for the first time, jet quenching is connected with the search of CEP.
{"title":"Critical Opalescence and Its Impact on the Jet Quenching Parameter q^","authors":"Jing Wu, Shanshan Cao, Feng Li","doi":"10.1088/0256-307x/41/3/031202","DOIUrl":"https://doi.org/10.1088/0256-307x/41/3/031202","url":null,"abstract":"Jet quenching parameter <inline-formula>\u0000<tex-math>\u0000<?CDATA $hat{q}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mover accent=\"true\"><mml:mi>q</mml:mi><mml:mo>^</mml:mo></mml:mover></mml:math>\u0000<inline-graphic xlink:href=\"cpl_41_3_031202_ieqn3.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> is essential for characterizing the interaction strength between jet partons and nuclear matter. Based on the quark-meson model, we develop a new framework for calculating <inline-formula>\u0000<tex-math>\u0000<?CDATA $hat{q}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mover accent=\"true\"><mml:mi>q</mml:mi><mml:mo>^</mml:mo></mml:mover></mml:math>\u0000<inline-graphic xlink:href=\"cpl_41_3_031202_ieqn4.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> at finite chemical potentials, in which <inline-formula>\u0000<tex-math>\u0000<?CDATA $hat{q}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mover accent=\"true\"><mml:mi>q</mml:mi><mml:mo>^</mml:mo></mml:mover></mml:math>\u0000<inline-graphic xlink:href=\"cpl_41_3_031202_ieqn5.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> is related to the spectral function of the chiral order parameter. A mean field perturbative calculation up to the one-loop order indicates that the momentum broadening of jets is enhanced at both high temperature and high chemical potential, and approximately proportional to the parton number density in the partonic phase. We further investigate the behavior of <inline-formula>\u0000<tex-math>\u0000<?CDATA $hat{q}$?>\u0000</tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mover accent=\"true\"><mml:mi>q</mml:mi><mml:mo>^</mml:mo></mml:mover></mml:math>\u0000<inline-graphic xlink:href=\"cpl_41_3_031202_ieqn6.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> in the vicinity of the critical endpoint (CEP) by coupling our calculation with a recently developed equation of state that includes a CEP in the universality class of the Ising model, from which we discover the partonic critical opalescence, i.e., the divergence of scattering rate of jets and their momentum broadening at the CEP, contributed by scatterings via the <italic toggle=\"yes\">σ</italic> exchange process. Hence, for the first time, jet quenching is connected with the search of CEP.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140568375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We report a linear-scaling random Green’s function (rGF) method for large-scale electronic structure calculation. In this method, the rGF is defined on a set of random states and is efficiently calculated by projecting onto Krylov subspace. With the rGF method, the Fermi–Dirac operator can be obtained directly, avoiding the polynomial expansion to Fermi–Dirac function. To demonstrate the applicability, we implement the rGF method with the density-functional tight-binding method. It is shown that the Krylov subspace can maintain at small size for materials with different gaps at zero temperature, including H2O and Si clusters. We find with a simple deflation technique that the rGF self-consistent calculation of H2O clusters at T = 0 K can reach an error of ∼ 1 meV per H2O molecule in total energy, compared to deterministic calculations. The rGF method provides an effective stochastic method for large-scale electronic structure simulation.
{"title":"Random Green’s Function Method for Large-Scale Electronic Structure Calculation","authors":"Mingfa Tang, Chang Liu, Aixia Zhang, Qingyun Zhang, Jiayu Zhai, Shengjun Yuan, Youqi Ke","doi":"10.1088/0256-307x/41/5/053102","DOIUrl":"https://doi.org/10.1088/0256-307x/41/5/053102","url":null,"abstract":"We report a linear-scaling random Green’s function (rGF) method for large-scale electronic structure calculation. In this method, the rGF is defined on a set of random states and is efficiently calculated by projecting onto Krylov subspace. With the rGF method, the Fermi–Dirac operator can be obtained directly, avoiding the polynomial expansion to Fermi–Dirac function. To demonstrate the applicability, we implement the rGF method with the density-functional tight-binding method. It is shown that the Krylov subspace can maintain at small size for materials with different gaps at zero temperature, including H<sub>2</sub>O and Si clusters. We find with a simple deflation technique that the rGF self-consistent calculation of H<sub>2</sub>O clusters at <italic toggle=\"yes\">T</italic> = 0 K can reach an error of ∼ 1 meV per H<sub>2</sub>O molecule in total energy, compared to deterministic calculations. The rGF method provides an effective stochastic method for large-scale electronic structure simulation.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140929695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-01DOI: 10.1088/0256-307x/41/4/047101
R. Wang, Z. Song
A Moiré system is formed when two periodic structures have a slightly mismatched period, resulting in unusual strongly correlated states in the presence of particle-particle interactions. The periodic structures can arise from the intrinsic crystalline order and periodic external field. We investigate a one-dimensional Hubbard model with periodic on-site potential of period n0, which is commensurate to the lattice constant. For large n0, the exact solution demonstrates that there is a midgap flat band with zero energy in the absence of Hubbard interaction. Each Moiré unit cell contributes two zero energy levels to the flat band. In the presence of Hubbard interaction, the midgap physics is demonstrated to be well described by a uniform Hubbard chain in which the effective hopping and on-site interaction strength can be controlled by the amplitude and period of the external field. Numerical simulations are performed to demonstrate the correlated behaviors in the finite-sized Moiré Hubbard system, including the existence of an η-pairing state and bound pair oscillation. This finding provides a method to enhance the correlated effect by a spatially periodic external field.
{"title":"Flat Band and η-Pairing States in a One-Dimensional Moiré Hubbard Model","authors":"R. Wang, Z. Song","doi":"10.1088/0256-307x/41/4/047101","DOIUrl":"https://doi.org/10.1088/0256-307x/41/4/047101","url":null,"abstract":"A Moiré system is formed when two periodic structures have a slightly mismatched period, resulting in unusual strongly correlated states in the presence of particle-particle interactions. The periodic structures can arise from the intrinsic crystalline order and periodic external field. We investigate a one-dimensional Hubbard model with periodic on-site potential of period <italic toggle=\"yes\">n</italic>\u0000<sub>0</sub>, which is commensurate to the lattice constant. For large <italic toggle=\"yes\">n</italic>\u0000<sub>0</sub>, the exact solution demonstrates that there is a midgap flat band with zero energy in the absence of Hubbard interaction. Each Moiré unit cell contributes two zero energy levels to the flat band. In the presence of Hubbard interaction, the midgap physics is demonstrated to be well described by a uniform Hubbard chain in which the effective hopping and on-site interaction strength can be controlled by the amplitude and period of the external field. Numerical simulations are performed to demonstrate the correlated behaviors in the finite-sized Moiré Hubbard system, including the existence of an <italic toggle=\"yes\">η</italic>-pairing state and bound pair oscillation. This finding provides a method to enhance the correlated effect by a spatially periodic external field.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140929541","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-21DOI: 10.1088/0256-307x/41/4/047801
Daiqiang Huang, Yang Wang, He Wang, Jian Wang, Yang Liu
Novel electron states stabilized by Coulomb interactions attract tremendous interests in condensed matter physics. These states are studied by corresponding phase transitions occurring at extreme conditions such as mK-temperatures and high magnetic field. In this work, we introduce a magneto-optical Kerr effect (MOKE) measurement system to comprehensively explore these phases in addition to conventional transport measurement. This system, composed of an all-fiber zero-loop Sagnac interferometer and in-situ piezo-scanner inside a dilution refrigerator, operates below 100 millikelvin, with a maximum field of 12 Tesla and has a resolution as small as 0.2 $mu rad$. As a demonstration, we investigate TbMn$_6mathrm{Sn}_6$, where the manganese atoms form Kagome lattice that hosts topological non-trivial Dirac cones. We observed two types of Kerr signals, stemming from its fully polarized ferromagnetic ground state and positive charged carriers within the Dirac-like dispersion.
{"title":"Magneto-optic Kerr Effect Measurement of TbMn6Sn6 at mK-Temperature","authors":"Daiqiang Huang, Yang Wang, He Wang, Jian Wang, Yang Liu","doi":"10.1088/0256-307x/41/4/047801","DOIUrl":"https://doi.org/10.1088/0256-307x/41/4/047801","url":null,"abstract":"\u0000 Novel electron states stabilized by Coulomb interactions attract tremendous interests in condensed matter physics. These states are studied by corresponding phase transitions occurring at extreme conditions such as mK-temperatures and high magnetic field. In this work, we introduce a magneto-optical Kerr effect (MOKE) measurement system to comprehensively explore these phases in addition to conventional transport measurement. This system, composed of an all-fiber zero-loop Sagnac interferometer and in-situ piezo-scanner inside a dilution refrigerator, operates below 100 millikelvin, with a maximum field of 12 Tesla and has a resolution as small as 0.2 $mu rad$. As a demonstration, we investigate TbMn$_6mathrm{Sn}_6$, where the manganese atoms form Kagome lattice that hosts topological non-trivial Dirac cones. We observed two types of Kerr signals, stemming from its fully polarized ferromagnetic ground state and positive charged carriers within the Dirac-like dispersion.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140222476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Two-dimensional (2D) van der Waals magnetic materials have demonstrated promising and versatile electronic and magnetic properties in the 2D limit, indicating a considerable potential to advance spintronic applications. Theoretical predictions thus far have not ascertained whether monolayer VCl3 is a ferromagnetic (FM) or anti-FM monolayer; this also remains to be experimentally verified. This study entailed a theoretical investigation of the influence of potential factors, including C3 symmetry breaking, orbital ordering, epitaxial strain, and charge doping, on the magnetic ground state. Utilizing first-principles calculations, we predicted a collinear Type-III FM ground state in monolayer VCl3 with a broken C3 symmetry, wherein only the former two of three t 2gorbitals (a 1g, e π g2, and e π g1) are occupied. The atomic layer thickness and bond angles of monolayer VCl3 undergo abrupt changes driven by an orbital ordering switch, resulting in concomitant structural and magnetic phase transitions. Introducing doping to the underlying Cl atoms of monolayer VCl3 without C3 symmetry simultaneously induces in- and out-of-plane polarizations. This can achieve a multiferroic phase transition if combined with the discovered adjustments of magnetic ground state and polarization magnitude under strain. The establishment of an orbital-ordering driven regulatory mechanism can facilitate deeper exploration and comprehension of magnetic properties of strongly correlated systems in monolayer VCl3.
二维（2D）范德华磁性材料在二维极限中表现出了前景广阔的多功能电子和磁性能，这表明它们在推动自旋电子应用方面具有相当大的潜力。迄今为止，理论预测尚未确定单层 VCl3 是铁磁（FM）单层还是反 FM 单层；这一点也有待实验验证。本研究需要对潜在因素（包括 C3 对称性破坏、轨道有序化、外延应变和电荷掺杂）对磁基态的影响进行理论研究。利用第一原理计算，我们预测了单层 VCl3 中具有 C3 对称性破缺的共线 III 型调频基态，其中三个 t 2 轨道（a 1g、e π g2 和 e π g1）中只有前两个被占据。在轨道有序转换的驱动下，单层 VCl3 的原子层厚度和键角发生了突变，从而导致结构和磁性相变。在无 C3 对称性的单层 VCl3 底层 Cl 原子中引入掺杂物，可同时诱导面内和面外极化。如果结合已发现的磁基态调整和应变下的极化幅度，就能实现多铁性相变。轨道排序驱动调节机制的建立有助于深入探索和理解单层 VCl3 中强相关系统的磁性。
{"title":"Orbital-ordering driven simultaneous tunability of magnetism and electric polarization in strained monolayer VCl3","authors":"Deping Guo, Cong Wang, Lvjin Wang, Yunhao Lu, Hua Wu, Yanning Zhang, Wei Ji","doi":"10.1088/0256-307x/41/4/047501","DOIUrl":"https://doi.org/10.1088/0256-307x/41/4/047501","url":null,"abstract":"\u0000 Two-dimensional (2D) van der Waals magnetic materials have demonstrated promising and versatile electronic and magnetic properties in the 2D limit, indicating a considerable potential to advance spintronic applications. Theoretical predictions thus far have not ascertained whether monolayer VCl3 is a ferromagnetic (FM) or anti-FM monolayer; this also remains to be experimentally verified. This study entailed a theoretical investigation of the influence of potential factors, including C3 symmetry breaking, orbital ordering, epitaxial strain, and charge doping, on the magnetic ground state. Utilizing first-principles calculations, we predicted a collinear Type-III FM ground state in monolayer VCl3 with a broken C3 symmetry, wherein only the former two of three t\u0000 2gorbitals (a\u0000 1g, e\u0000 π\u0000 g2, and e\u0000 π\u0000 g1) are occupied. The atomic layer thickness and bond angles of monolayer VCl3 undergo abrupt changes driven by an orbital ordering switch, resulting in concomitant structural and magnetic phase transitions. Introducing doping to the underlying Cl atoms of monolayer VCl3 without C3 symmetry simultaneously induces in- and out-of-plane polarizations. This can achieve a multiferroic phase transition if combined with the discovered adjustments of magnetic ground state and polarization magnitude under strain. The establishment of an orbital-ordering driven regulatory mechanism can facilitate deeper exploration and comprehension of magnetic properties of strongly correlated systems in monolayer VCl3.","PeriodicalId":10344,"journal":{"name":"Chinese Physics Letters","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140222308","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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