Pub Date : 2024-10-04DOI: 10.1016/j.physe.2024.116118
A.O. Sboychakov, A.L. Rakhmanov, A.V. Rozhkov
This work theoretically analyzes electronic ordering in AA-stacked bilayer graphene and the role of the Coulomb interaction in these many-body phenomena. Using the random phase approximation to account for screening, we find intra-layer effective interactions to be much stronger than inter-layer interactions; under certain circumstances, the latter may also become attractive. At zero doping, the Coulomb repulsion stabilizes the spin-density wave state, with a Néel temperature in the tens of Kelvin. While dominant in the undoped system, the spin-density wave is destroyed by sufficiently strong doping and a superconducting phase emerges. We find that the effective Coulomb inter-layer interaction can give rise to superconductivity. However, the corresponding critical temperature is negligibly small, and phonon-mediated attraction must be introduced to observe it. Strong intra-layer repulsion suppresses order parameters that couple two intra-layer electrons. We point out a possible superconducting state with finite Cooper pair momentum.
这项研究从理论上分析了 AA 层叠双层石墨烯中的电子有序性以及库仑相互作用在这些多体现象中的作用。利用随机相近似来解释屏蔽，我们发现层内有效相互作用远强于层间相互作用；在某些情况下，后者还可能变得有吸引力。在零掺杂时，库仑斥力会稳定自旋密度波态，内尔温度为几十开尔文。虽然自旋密度波在未掺杂的体系中占主导地位，但足够强的掺杂会破坏自旋密度波，出现超导阶段。我们发现，有效的库仑层间相互作用可以产生超导。然而，相应的临界温度小得可以忽略不计，而且必须引入声子介导的吸引力才能观察到它。强烈的层内斥力会抑制耦合两个层内电子的阶次参数。我们指出了一种具有有限库珀对动量的可能超导状态。
{"title":"Superconductivity and spin density wave in AA stacked bilayer graphene","authors":"A.O. Sboychakov, A.L. Rakhmanov, A.V. Rozhkov","doi":"10.1016/j.physe.2024.116118","DOIUrl":"10.1016/j.physe.2024.116118","url":null,"abstract":"<div><div>This work theoretically analyzes electronic ordering in AA-stacked bilayer graphene and the role of the Coulomb interaction in these many-body phenomena. Using the random phase approximation to account for screening, we find intra-layer effective interactions to be much stronger than inter-layer interactions; under certain circumstances, the latter may also become attractive. At zero doping, the Coulomb repulsion stabilizes the spin-density wave state, with a Néel temperature in the tens of Kelvin. While dominant in the undoped system, the spin-density wave is destroyed by sufficiently strong doping and a superconducting phase emerges. We find that the effective Coulomb inter-layer interaction can give rise to superconductivity. However, the corresponding critical temperature is negligibly small, and phonon-mediated attraction must be introduced to observe it. Strong intra-layer repulsion suppresses order parameters that couple two intra-layer electrons. We point out a possible superconducting state with finite Cooper pair momentum.</div></div>","PeriodicalId":20181,"journal":{"name":"Physica E-low-dimensional Systems & Nanostructures","volume":"165 ","pages":"Article 116118"},"PeriodicalIF":2.9,"publicationDate":"2024-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142425337","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-10-03DOI: 10.1016/j.physe.2024.116120
Piotr Graczyk , Maria Pugaczowa-Michalska , Maciej Krawczyk
The generation of short spin-current pulses is essential for fast spintronic devices. So far, spin current pulses are generated by femtosecond laser pulses which drive spins from a ferromagnetic metal layer. However, the need for miniaturization, simplicity and energy efficiency favour electric-field control of spintronic devices over optic or thermal control. Here, we combine ab initio calculations of electronic density of states at MgO/Fe interface with continuous model for charge transport to investigate the dynamics of the spin-dependent potential. We demonstrate that the voltage-driven instability of the electronic band structure due to the electronic resonant states at the Fe/MgO interface results in the generation of the femtosecond spin-polarized current pulse with the spin polarization up to 00 % that propagates from the interface to the bulk. The dynamics of the current pulses driven by the Stoner instability depends neither on the dielectric relaxation time nor on the details of how the instability is achieved by changing the voltage, i.e. as long as the voltage changes are slow (quasi-static) with respect to the time determined by the spin diffusion constant, being of the order of fs. The presence of the instability can be detected by THz time-domain spectroscopy or pump-probe techniques.
短自旋电流脉冲的产生对快速自旋电子设备至关重要。迄今为止，自旋电流脉冲是由飞秒激光脉冲产生的，飞秒激光脉冲从铁磁性金属层驱动自旋。然而，由于对微型化、简便性和能效的需求，自旋电子器件的电场控制优于光学或热控制。在这里，我们将氧化镁/铁界面电子态密度的 ab initio 计算与电荷传输连续模型相结合，研究了自旋相关电势的动态。我们证明，由于氧化镁/铁界面上的电子共振态，电压驱动的电子能带结构的不稳定性导致产生飞秒自旋极化电流脉冲，其自旋极化高达 P=7 00 %，并从界面传播到主体。斯通纳不稳定性驱动的电流脉冲的动态既不取决于介电弛豫时间，也不取决于如何通过改变电压实现不稳定性的细节，也就是说，只要电压变化相对于自旋扩散常数决定的时间是缓慢的（准静态），即在 fs 量级。不稳定性的存在可以通过太赫兹时域光谱或泵浦探针技术检测到。
{"title":"Generation of femtosecond spin-polarized current pulses at Fe/MgO interface by quasi-static voltage","authors":"Piotr Graczyk , Maria Pugaczowa-Michalska , Maciej Krawczyk","doi":"10.1016/j.physe.2024.116120","DOIUrl":"10.1016/j.physe.2024.116120","url":null,"abstract":"<div><div>The generation of short spin-current pulses is essential for fast spintronic devices. So far, spin current pulses are generated by femtosecond laser pulses which drive spins from a ferromagnetic metal layer. However, the need for miniaturization, simplicity and energy efficiency favour electric-field control of spintronic devices over optic or thermal control. Here, we combine ab initio calculations of electronic density of states at MgO/Fe interface with continuous model for charge transport to investigate the dynamics of the spin-dependent potential. We demonstrate that the voltage-driven instability of the electronic band structure due to the electronic resonant states at the Fe/MgO interface results in the generation of the femtosecond spin-polarized current pulse with the spin polarization up to <span><math><mrow><mi>P</mi><mo>=</mo><mn>7</mn></mrow></math></span> 00 % that propagates from the interface to the bulk. The dynamics of the current pulses driven by the Stoner instability depends neither on the dielectric relaxation time nor on the details of how the instability is achieved by changing the voltage, i.e. as long as the voltage changes are slow (quasi-static) with respect to the time determined by the spin diffusion constant, being of the order of fs. The presence of the instability can be detected by THz time-domain spectroscopy or pump-probe techniques.</div></div>","PeriodicalId":20181,"journal":{"name":"Physica E-low-dimensional Systems & Nanostructures","volume":"165 ","pages":"Article 116120"},"PeriodicalIF":2.9,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142425063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-02DOI: 10.1016/j.physe.2024.116119
Mona Abdi , Bandar Astinchap , Farhad Khoeini
Extensive research is underway to improve the thermoelectric properties of materials by enhancing the figure of merit (ZT). In this study, we are investigating the thermoelectric properties of MoS2/MoTe2 and MoS2/MoSe2 lateral heterostructures (LH-S) under the influence of external magnetic fields (EMF) and transverse electric fields (TEF). We employ the non-equilibrium Green's function (N-EGF) and tight-binding (TB) methods for our analysis. The results obtained indicate that the ZT for MoS2-MoTe2 and MoS2-MoSe2 LH-S enhanced with an increase in the TEF. The ZT of MoS2-MoSe2 LH-S increases near room temperature, while the ZT of MoS2-MoTe2 LH-S increases with an increase in EMF across the entire temperature range. Additionally, the ZT for MoS2-MoSe2 LH-S increases with an increase in the nanoribbon width, whereas for MoS2-MoTe2 LH-S, it decreases. The results reveal that the semiconductor type of MoS2-MoSe2 and MoS2-MoTe2 LH-S changes from n-type to p-type when subjected to EMF and transverse TEF. The examination of the temperature dependence of ZT in the presence of TEF and EMF for MoS2-MoTe2 and MoS2-MoSe2 LH-S indicates that these structures are highly promising candidates for use in electrical devices.
{"title":"Thermoelectric properties of MoS2-MoTe2 and MoS2-MoSe2lateral hetero-structures: The effects of external magnetic, transverse electric fields and nanoribbon width","authors":"Mona Abdi , Bandar Astinchap , Farhad Khoeini","doi":"10.1016/j.physe.2024.116119","DOIUrl":"10.1016/j.physe.2024.116119","url":null,"abstract":"<div><div>Extensive research is underway to improve the thermoelectric properties of materials by enhancing the figure of merit (ZT). In this study, we are investigating the thermoelectric properties of MoS<sub>2</sub>/MoTe<sub>2</sub> and MoS<sub>2</sub>/MoSe<sub>2</sub> lateral heterostructures (LH-S) under the influence of external magnetic fields (EMF) and transverse electric fields (TEF). We employ the non-equilibrium Green's function (N-EGF) and tight-binding (TB) methods for our analysis. The results obtained indicate that the ZT for MoS<sub>2</sub>-MoTe<sub>2</sub> and MoS<sub>2</sub>-MoSe<sub>2</sub> LH-S enhanced with an increase in the TEF. The ZT of MoS<sub>2</sub>-MoSe<sub>2</sub> LH-S increases near room temperature, while the ZT of MoS<sub>2</sub>-MoTe<sub>2</sub> LH-S increases with an increase in EMF across the entire temperature range. Additionally, the ZT for MoS<sub>2</sub>-MoSe<sub>2</sub> LH-S increases with an increase in the nanoribbon width, whereas for MoS<sub>2</sub>-MoTe<sub>2</sub> LH-S, it decreases. The results reveal that the semiconductor type of MoS<sub>2</sub>-MoSe<sub>2</sub> and MoS<sub>2</sub>-MoTe<sub>2</sub> LH-S changes from n-type to p-type when subjected to EMF and transverse TEF. The examination of the temperature dependence of ZT in the presence of TEF and EMF for MoS<sub>2</sub>-MoTe<sub>2</sub> and MoS<sub>2</sub>-MoSe<sub>2</sub> LH-S indicates that these structures are highly promising candidates for use in electrical devices.</div></div>","PeriodicalId":20181,"journal":{"name":"Physica E-low-dimensional Systems & Nanostructures","volume":"165 ","pages":"Article 116119"},"PeriodicalIF":2.9,"publicationDate":"2024-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142425343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 develop a method to calculate the electron flow between an arbitrary atomic monolayer sheet and an arbitrary tube by expressing the corresponding sheet-tube tunneling matrix elements with those between sheets. We use this method to calculate the spin current from a monolayer silicene sheet with sublattice-staggered current-induced spin polarization to a silicene tube. The calculated sheet-to-tube spin current exhibits an oscillation as a function of the tube circumferential length because the Fermi points in the tube cross the Fermi circle in the sheet. Furthermore, the spin current with spin in the out-of-plane direction, which is absent in the sheet-sheet junction (including twisted sheets) with rotational symmetry, appears in an oscillating form in the tube-sheet junction due to the broken rotational symmetry. This is an example of the symmetry manipulation which realizes switching a particular component of the spin current.
{"title":"Transport through a monolayer-tube junction: Sheet-to-tube spin current","authors":"Yuma Kitagawa , Yuta Suzuki , Shin-ichiro Tezuka , Hiroshi Akera","doi":"10.1016/j.physe.2024.116111","DOIUrl":"10.1016/j.physe.2024.116111","url":null,"abstract":"<div><div>We develop a method to calculate the electron flow between an arbitrary atomic monolayer sheet and an arbitrary tube by expressing the corresponding sheet-tube tunneling matrix elements with those between sheets. We use this method to calculate the spin current from a monolayer silicene sheet with sublattice-staggered current-induced spin polarization to a silicene tube. The calculated sheet-to-tube spin current exhibits an oscillation as a function of the tube circumferential length because the Fermi points in the tube cross the Fermi circle in the sheet. Furthermore, the spin current with spin in the out-of-plane direction, which is absent in the sheet-sheet junction (including twisted sheets) with <span><math><msub><mrow><mi>C</mi></mrow><mrow><mn>3</mn></mrow></msub></math></span> rotational symmetry, appears in an oscillating form in the tube-sheet junction due to the broken <span><math><msub><mrow><mi>C</mi></mrow><mrow><mn>3</mn></mrow></msub></math></span> rotational symmetry. This is an example of the symmetry manipulation which realizes switching a particular component of the spin current.</div></div>","PeriodicalId":20181,"journal":{"name":"Physica E-low-dimensional Systems & Nanostructures","volume":"165 ","pages":"Article 116111"},"PeriodicalIF":2.9,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142425064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-10-01DOI: 10.1016/j.physe.2024.116117
Shalini Kumari , Neha Dhull , Weichang Lin , Zonghuan Lu , Joan Redwing , Toh-Ming Lu , Gwo-Ching Wang
Transition-metal dichalcogenides and their heterostructures have attractive potential applications in electronics and optoelectronics. Wafer scale 1 to 3 monolayers WS2 and MoS2 ultrathin films on GaN/sapphire substrates were grown by metal organic chemical vapor deposition. Azimuthal reflection high-energy electron diffraction (ARHEED) was used to characterize the long-range order of these TMDC ultrathin films. The RHEED patterns of WS2 and MoS2 show stripes and arcs but the MoS2 on GaN shows sharp spots in addition to stripes and arcs. The 2D map constructed from ARHEED patterns shows that WS2 is epitaxial and has an in-plane domain orientation dispersion. For the MoS2 on GaN/sapphire substrate, the 2D map shows concentric continuous rings for each diffraction order of MoS2 and GaN indicating that the in-plane MoS2 domain orientation and GaN nanocrystals are random. The out-of-plane orientation dispersion of MoS2 on the GaN substrate is larger than that of WS2 on the GaN substrate. The observations of stripes, arcs, and spots from RHEED patterns and the 2D maps reveal the deviation of ultrathin epitaxial films from its perfect epitaxy, especially the TMDC domain orientation dispersion over a large area. These rich findings from 2D maps broaden the application of ARHEED in more than one monolayer thick 2D materials.
{"title":"In-plane and out-of-plane domain orientation dispersions in 1 to 3 monolayers epitaxial WS2 and MoS2 films on GaN(0001) film/sapphire(0001)","authors":"Shalini Kumari , Neha Dhull , Weichang Lin , Zonghuan Lu , Joan Redwing , Toh-Ming Lu , Gwo-Ching Wang","doi":"10.1016/j.physe.2024.116117","DOIUrl":"10.1016/j.physe.2024.116117","url":null,"abstract":"<div><div>Transition-metal dichalcogenides and their heterostructures have attractive potential applications in electronics and optoelectronics. Wafer scale 1 to 3 monolayers WS<sub>2</sub> and MoS<sub>2</sub> ultrathin films on GaN/sapphire substrates were grown by metal organic chemical vapor deposition. Azimuthal reflection high-energy electron diffraction (ARHEED) was used to characterize the long-range order of these TMDC ultrathin films. The RHEED patterns of WS<sub>2</sub> and MoS<sub>2</sub> show stripes and arcs but the MoS<sub>2</sub> on GaN shows sharp spots in addition to stripes and arcs. The 2D map constructed from ARHEED patterns shows that WS<sub>2</sub> is epitaxial and has an in-plane domain orientation dispersion. For the MoS<sub>2</sub> on GaN/sapphire substrate, the 2D map shows concentric continuous rings for each diffraction order of MoS<sub>2</sub> and GaN indicating that the in-plane MoS<sub>2</sub> domain orientation and GaN nanocrystals are random. The out-of-plane orientation dispersion of MoS<sub>2</sub> on the GaN substrate is larger than that of WS<sub>2</sub> on the GaN substrate. The observations of stripes, arcs, and spots from RHEED patterns and the 2D maps reveal the deviation of ultrathin epitaxial films from its perfect epitaxy, especially the TMDC domain orientation dispersion over a large area. These rich findings from 2D maps broaden the application of ARHEED in more than one monolayer thick 2D materials.</div></div>","PeriodicalId":20181,"journal":{"name":"Physica E-low-dimensional Systems & Nanostructures","volume":"165 ","pages":"Article 116117"},"PeriodicalIF":2.9,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142425332","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
The 1D Anderson model featuring uncorrelated diagonal disorder is considered. The wavefunction statistics associated to transitions between distinct locations is analyzed. In the presence of mild disorder, the local squared wavefunctions, that is occupation probabilities, obey exponential statistics. When disorder is high, amplitudes measured near the input site are well described by Rician distributions, a form of sub-exponential statistics, due to the influence of strongly localized modes. This results in a reduced likelihood of rogue wave events. When the statistics is taken over various disorder realizations or locations, the lack of knowledge over the rate of the exponential processes acting locally yields long-tailed distributions. As a consequence, rogue waves become more frequent at locations closer to the input for increasing disorder strength. Our findings can be used to assess the occurrence of extreme events as well as the degree of localization over a broad class of disordered models.
{"title":"Rogue-wave statistics in Anderson chains","authors":"M.F.V. Oliveira , A.M.C. Souza , M.L. Lyra , F.A.B.F. de Moura , G.M.A. Almeida","doi":"10.1016/j.physe.2024.116114","DOIUrl":"10.1016/j.physe.2024.116114","url":null,"abstract":"<div><div>The 1D Anderson model featuring uncorrelated diagonal disorder is considered. The wavefunction statistics associated to transitions between distinct locations is analyzed. In the presence of mild disorder, the local squared wavefunctions, that is occupation probabilities, obey exponential statistics. When disorder is high, amplitudes measured near the input site are well described by Rician distributions, a form of sub-exponential statistics, due to the influence of strongly localized modes. This results in a reduced likelihood of rogue wave events. When the statistics is taken over various disorder realizations or locations, the lack of knowledge over the rate of the exponential processes acting locally yields long-tailed distributions. As a consequence, rogue waves become more frequent at locations closer to the input for increasing disorder strength. Our findings can be used to assess the occurrence of extreme events as well as the degree of localization over a broad class of disordered models.</div></div>","PeriodicalId":20181,"journal":{"name":"Physica E-low-dimensional Systems & Nanostructures","volume":"165 ","pages":"Article 116114"},"PeriodicalIF":2.9,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142358030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-09-28DOI: 10.1016/j.physe.2024.116112
B. Aghalli , H. Khandan Fadafan , M.B. Bagherieh Najjar
This study presents the synthesis and comprehensive evaluation of nanocrystalline CoxNi0.5-xMn0.5Fe2O4 (0.0 ≤ x ≤ 0.5) ferrites. Utilizing a variety of analytical techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV–Vis) spectroscopy, field emission scanning electron microscopy (FESEM), and vibrating sample magnetometry (VSM), we characterized the structural, optical, elastic, and magnetic properties of the synthesized nanoparticles. Our findings reveal that increasing Co content leads to a systematic increase in lattice constant from 8.33 Å to 8.39 Å and influences the crystallite size, which ranges between 10 and 15 nm as determined by XRD. Notably, the band gaps of these nanoparticles span from 2.8 to 3.6 eV, varying with Co concentration. Magnetic measurements indicate a transition from superparamagnetic-like behavior at x = 0 to enhanced saturation magnetization, remanence, and coercivity with higher Co content. The novelty of this research lies in the detailed correlation between Co substitution and the resultant changes in multiple physical properties of NiMn nanoferrite, offering potential applications in various technological fields such as magnetic storage, sensors, and biomedical applications.
本研究介绍了纳米晶 CoxNi0.5-xMn0.5Fe2O4 (0.0 ≤ x ≤ 0.5) 铁氧体的合成和综合评估。我们利用多种分析技术，包括 X 射线衍射 (XRD)、傅立叶变换红外光谱 (FTIR)、紫外可见光谱 (UV-Vis)、场发射扫描电子显微镜 (FESEM) 和振动样品磁力计 (VSM)，对合成纳米粒子的结构、光学、弹性和磁性能进行了表征。我们的研究结果表明，钴含量的增加会导致晶格常数从 8.33 Å 系统性地增加到 8.39 Å，并影响晶粒大小，X 射线衍射仪测定的晶粒大小在 10 到 15 nm 之间。值得注意的是，这些纳米粒子的带隙在 2.8 至 3.6 eV 之间，随 Co 浓度的变化而变化。磁性测量结果表明，随着钴含量的增加，从 x = 0 时的超顺磁性行为过渡到饱和磁化、剩磁和矫顽力的增强。这项研究的新颖之处在于，镍锰纳米铁氧体的钴替代与多种物理性质的变化之间存在着详细的关联，这为磁存储、传感器和生物医学应用等各种技术领域提供了潜在的应用前景。
{"title":"Characterization of Co-doped Ni-Mn spinel nanoferrites: A Multi-faceted evaluation of structural, optical, elastic, and magnetic properties","authors":"B. Aghalli , H. Khandan Fadafan , M.B. Bagherieh Najjar","doi":"10.1016/j.physe.2024.116112","DOIUrl":"10.1016/j.physe.2024.116112","url":null,"abstract":"<div><div>This study presents the synthesis and comprehensive evaluation of nanocrystalline Co<sub>x</sub>Ni<sub>0.5-x</sub>Mn<sub>0.5</sub>Fe<sub>2</sub>O<sub>4</sub> (0.0 ≤ x ≤ 0.5) ferrites. Utilizing a variety of analytical techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV–Vis) spectroscopy, field emission scanning electron microscopy (FESEM), and vibrating sample magnetometry (VSM), we characterized the structural, optical, elastic, and magnetic properties of the synthesized nanoparticles. Our findings reveal that increasing Co content leads to a systematic increase in lattice constant from 8.33 Å to 8.39 Å and influences the crystallite size, which ranges between 10 and 15 nm as determined by XRD. Notably, the band gaps of these nanoparticles span from 2.8 to 3.6 eV, varying with Co concentration. Magnetic measurements indicate a transition from superparamagnetic-like behavior at x = 0 to enhanced saturation magnetization, remanence, and coercivity with higher Co content. The novelty of this research lies in the detailed correlation between Co substitution and the resultant changes in multiple physical properties of NiMn nanoferrite, offering potential applications in various technological fields such as magnetic storage, sensors, and biomedical applications.</div></div>","PeriodicalId":20181,"journal":{"name":"Physica E-low-dimensional Systems & Nanostructures","volume":"165 ","pages":"Article 116112"},"PeriodicalIF":2.9,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142358032","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-09-28DOI: 10.1016/j.physe.2024.116116
Jing-Jing He , Jia-Bei Dong , Ying Zhang , Qin-Yue Cao , Ling-Xiao Liu , Jun-Yi Gu , Min Hua , Jia-Ren Yuan , Xiao-Hong Yan
To meet the demands of low-power micromaterials applications, the generation of pure spin currents in spintronics by utilizing an effective thermal spin conversion mechanism has become a hot topic among researchers. In this paper, based on the newly reported novel 2D P3S monolayer, various P3S nanoribbons with different edge atom arrangements are formed by one-dimensional tailoring. Intriguingly, the original nonmagnetism is broken in both armchair and zigzag orientations, introducing ferromagnetism contributed mainly by the 3p orbitals of the edge P atoms. More importantly, all bare nanoribbons exhibit peculiar transmission spectra with transmission peaks of opposite spin components located on both sides of the Fermi level. This apparent bipolar magnetic semiconductor property leads to a considerable spin Seebeck coefficient of ∼3 mV/K, which successfully suppresses the charge current and excites a giant spin current. Furthermore, the significant spin-dependent Seebeck effect is robust to width. The bi-directional superior spin thermoelectric properties, simple clipping method, and width robustness make the P3S nanoribbons promising and competitive in spintronic devices.
为满足低功耗微材料应用的需求，利用有效的热自旋转换机制在自旋电子学中产生纯自旋电流已成为研究人员的热门话题。本文以最新报道的新型二维 P3S 单层为基础，通过一维裁剪形成了具有不同边缘原子排列的各种 P3S 纳米带。有趣的是，原有的非磁性在扶手椅和之字形方向上都被打破，引入了主要由边缘 P 原子的 3p 轨道贡献的铁磁性。更重要的是，所有裸纳米带都显示出奇特的透射光谱，在费米级两侧都有自旋成分相反的透射峰。这种明显的双极磁性半导体特性导致自旋塞贝克系数 Ss 达到 ∼3 mV/K，从而成功地抑制了电荷电流并激发了巨大的自旋电流。此外，显著的自旋相关塞贝克效应对宽度具有稳健性。双向卓越的自旋热电特性、简单的削波方法和宽度稳健性使 P3S 纳米带在自旋电子器件中大有可为并具有竞争力。
{"title":"P3S nanoribbons with bi-directional superior spin thermoelectric properties","authors":"Jing-Jing He , Jia-Bei Dong , Ying Zhang , Qin-Yue Cao , Ling-Xiao Liu , Jun-Yi Gu , Min Hua , Jia-Ren Yuan , Xiao-Hong Yan","doi":"10.1016/j.physe.2024.116116","DOIUrl":"10.1016/j.physe.2024.116116","url":null,"abstract":"<div><div>To meet the demands of low-power micromaterials applications, the generation of pure spin currents in spintronics by utilizing an effective thermal spin conversion mechanism has become a hot topic among researchers. In this paper, based on the newly reported novel 2D P<sub>3</sub>S monolayer, various P<sub>3</sub>S nanoribbons with different edge atom arrangements are formed by one-dimensional tailoring. Intriguingly, the original nonmagnetism is broken in both armchair and zigzag orientations, introducing ferromagnetism contributed mainly by the 3<em>p</em> orbitals of the edge P atoms. More importantly, all bare nanoribbons exhibit peculiar transmission spectra with transmission peaks of opposite spin components located on both sides of the Fermi level. This apparent bipolar magnetic semiconductor property leads to a considerable spin Seebeck coefficient <span><math><mrow><msub><mi>S</mi><mi>s</mi></msub></mrow></math></span> of ∼3 mV/K, which successfully suppresses the charge current and excites a giant spin current. Furthermore, the significant spin-dependent Seebeck effect is robust to width. The bi-directional superior spin thermoelectric properties, simple clipping method, and width robustness make the P<sub>3</sub>S nanoribbons promising and competitive in spintronic devices.</div></div>","PeriodicalId":20181,"journal":{"name":"Physica E-low-dimensional Systems & Nanostructures","volume":"165 ","pages":"Article 116116"},"PeriodicalIF":2.9,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142425342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}
In the n-InGaAs/GaAs double quantum well, the suppression of resonant resistance by an in-plane magnetic field B ≤ 9 T in the temperature range T = (1.8–70) K is studied. The electron quantum lifetime, τq, is determined and the contributions of various scattering mechanisms to τq(T) are separated. It is shown that the observed nonmonotonic temperature dependence of the electron quantum lifetime is due to a combination of the interference contribution from the exchange electron-electron interaction in the ballistic regime and the inelastic electron-electron scattering in the diffusion regime (Fukuyama-Abrahams mechanism).
在 n-InGaAs/GaAs 双量子阱中，研究了在温度范围 T = (1.8-70) K 内平面磁场 B ≤ 9 T 对谐振电阻的抑制作用。确定了电子量子寿命τq，并分离了各种散射机制对τq(T)的贡献。研究表明，所观察到的电子量子寿命的非单调温度依赖性是由弹道机制中电子-电子交换相互作用的干涉贡献和扩散机制中的非弹性电子-电子散射（福山-亚伯拉罕机制）共同造成的。
{"title":"Temperature dependence of the electron quantum lifetime in InGaAs/GaAs double quantum well: Fukuyama-Abrahams mechanism","authors":"S.V. Gudina, Yu.G. Arapov, V.N. Neverov, A.P. Savelyev, N.S. Sandakov, N.G. Shelushinina, M.V. Yakunin","doi":"10.1016/j.physe.2024.116113","DOIUrl":"10.1016/j.physe.2024.116113","url":null,"abstract":"<div><div>In the n-InGaAs/GaAs double quantum well, the suppression of resonant resistance by an in-plane magnetic field <em>B</em> ≤ 9 T in the temperature range <em>T</em> = (1.8–70) K is studied. The electron quantum lifetime, <em>τ</em><sub><em>q</em></sub>, is determined and the contributions of various scattering mechanisms to <em>τ</em><sub><em>q</em></sub>(<em>T</em>) are separated. It is shown that the observed nonmonotonic temperature dependence of the electron quantum lifetime is due to a combination of the interference contribution from the exchange electron-electron interaction in the ballistic regime and the inelastic electron-electron scattering in the diffusion regime (Fukuyama-Abrahams mechanism).</div></div>","PeriodicalId":20181,"journal":{"name":"Physica E-low-dimensional Systems & Nanostructures","volume":"165 ","pages":"Article 116113"},"PeriodicalIF":2.9,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142425344","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2024-09-26DOI: 10.1016/j.physe.2024.116110
Ruixue Bai , Yaojie Zhu , Xilin Zhang , Yulun Liu , Zuowei Yan , Hui Ma , Chongyun Jiang
Heterojunction devices based on low-dimensional materials have the potential for convenient and efficient photodetection applications. In this study, we demonstrate a van der Waals (vdW) heterojunction device constructed by p-ZrGeTe4 and n-MoS2. Forming a p-n junction, the response speed of the device increased by 6 orders of magnitude compared to devices with individual MoS2. To further improve the responsivity of the device, a bipolar phototransistor (PTD) was prepared based on the p-n junction. The PTD achieves the photocurrent gain of almost 40. This PTD achieves high responsivity of 1.48 A W−1, and the corresponding specific detectivity can reach 3 × 1014 Jones in low frequencies. Under low frequencies, the noise of the device is dominated by generation–recombination noise; and as the frequency increases, it gradually becomes dominated by 1/f noise. The PTD is competitive in optoelectronics and promising in high-performance integrated devices.
{"title":"The enhanced characteristics of bipolar phototransistor with huge amplification","authors":"Ruixue Bai , Yaojie Zhu , Xilin Zhang , Yulun Liu , Zuowei Yan , Hui Ma , Chongyun Jiang","doi":"10.1016/j.physe.2024.116110","DOIUrl":"10.1016/j.physe.2024.116110","url":null,"abstract":"<div><div>Heterojunction devices based on low-dimensional materials have the potential for convenient and efficient photodetection applications. In this study, we demonstrate a van der Waals (vdW) heterojunction device constructed by <em>p</em>-ZrGeTe<sub>4</sub> and <em>n</em>-MoS<sub>2</sub>. Forming a <em>p-n</em> junction, the response speed of the device increased by 6 orders of magnitude compared to devices with individual MoS<sub>2</sub>. To further improve the responsivity of the device, a bipolar phototransistor (PTD) was prepared based on the <em>p-n</em> junction. The PTD achieves the photocurrent gain of almost 40. This PTD achieves high responsivity of 1.48 A W<sup>−1</sup>, and the corresponding specific detectivity can reach 3 × 10<sup>14</sup> Jones in low frequencies. Under low frequencies, the noise of the device is dominated by generation–recombination noise; and as the frequency increases, it gradually becomes dominated by 1/<em>f</em> noise. The PTD is competitive in optoelectronics and promising in high-performance integrated devices.</div></div>","PeriodicalId":20181,"journal":{"name":"Physica E-low-dimensional Systems & Nanostructures","volume":"165 ","pages":"Article 116110"},"PeriodicalIF":2.9,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142358031","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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