Shunsuke A. Sato
We theoretically investigate field-induced charge-transport processes from the viewpoint of time-reversal symmetry. We analytically demonstrate that breaking of the time-reversal symmetry is a necessary condition to induce charge-transport and direct-current by external fields. This finding provides microscopic insights into photovoltaic effects and optical-control of currents.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
继续探索
The development of van der Waals (vdW) crystals and their heterostructures has created a fascinating platform for exploring optoelectronic properties in the two-dimensional (2D) limit. With the recent discovery of 2D magnets, the control of the spin degree of freedom can be integrated to realize 2D spin-optoelectronics with spontaneous time-reversal symmetry breaking. Here, we report spin photovoltaic effects in vdW heterostructures of atomically thin magnet chromium triiodide (CrI3) sandwiched by graphene contacts. In the absence of a magnetic field, the photocurrent displays a distinct depen…
We investigate the bulk photovoltaic effect, which rectifies light into electric current, in a collective quantum state with correlation driven electronic ferroelectricity. We show via explicit real-time dynamical calculations that the effect of the applied electric field on the electronic order parameter leads to a strong enhancement of the bulk photovoltaic effect relative to the values obtained in a conventional insulator. The enhancements include both resonant enhancements at sub-band-gap frequencies, arising from excitation of optically active collective modes, and broadband enhancements …
We theoretically study the circularly polarized light-induced Floquet state in line-node semimetals with time-reversal symmetry and inversion symmetry. It is found that the Floquet state can show the photovoltaic anomalous Hall effect when an applied circularly polarized light gaps out the line node in the bulk and leave Weyl point nodes. The Hall conductivity is sensitive to the location of Fermi level: When the Fermi level locates at the node, the Hall conductivity depends on the radius of line node and is nearly independent of the intensity of light. Away from the line node, the Hall conduc…
Layer photovoltaic effect in van der Waals heterostructures
本文提出非中心对称范德华异质结中存在可通过光照控制的层光伏效应（LPE），系统分类了其依赖对称性的多种机制，并发现该效应在太赫兹频段具有可观的极化率，可作为体光伏探测的新手段。
Anomalous shift and optical vorticity in the steady photovoltaic current
本文研究了非中心对称半导体稳态光生伏特电流中的反常位移与光学涡度，发现带内弛豫和辐射复合诱导的位移远大于带间激发位移，并归因于带内 Berry 曲率和带间 Berry 相位拓扑奇点，无需精细调谐即可产生量级为 $mAV^{-2}$ 的非线性电导率。
Graphene is a promising candidate for optoelectronic applications such as photodetectors, terahertz imagers, and plasmonic devices. The origin of photoresponse in graphene junctions has been studied extensively and is attributed to either thermoelectric or photovoltaic effects. In addition, hot carrier transport and carrier multiplication are thought to play an important role. Here we report the intrinsic photoresponse in biased but otherwise homogeneous graphene. In this classic photoconductivity experiment, the thermoelectric effects are insignificant. Instead, the photovoltaic and a photo-i…
Vortex-enhanced photovoltaic current in disordered topological materials
研究发现无序拓扑材料中，动量空间的光学涡旋结构通过增强电子-杂质斜散射来提升体光伏电流，其频率指数和光伏张量约束依赖于拓扑材料类别、缺陷对称性和光偏振。
Bulk photovoltaic effects in the Haldane model
本文研究了Haldane模型中的体光伏效应，推导了镜面-时间对称性对电导率张量的约束，发现线偏振光可诱导位移和注入电流，而圆偏振光受三重旋转对称性限制不能诱导，并揭示了拓扑相变中电流符号变化与量子几何的微观联系。
Weyl semimetals (WSM) have been discovered in time-reversal symmetric materials, featuring monopoles of Berry's curvature in momentum space. WSM have been distinguished between Type-I and II where the velocity tilting of the cone in the later ensures a finite area Fermi surface. To date it has not been clear whether the two types results in any qualitatively new phenomena. Here we focus on the shift-current response ($σ_{shift}(ω)$), a second order optical effect generating photocurrents. Surprisingly we find that up to an order unity constant, $σ_{shift}(ω)\sim \frac{e^3}{h^2}\frac{1}ω$ in Ty…
The generation of photocurrent in condensed matter is of main interest for photovoltaic and optoelectronic applications. Shift current, a nonlinear photoresponse, has attracted recent intensive attention as a dominant player of bulk photovoltaic effect in ferroelectric materials. In three dimensional topological insulators $\text{Bi}_2\text{X}_3$ (X: Te, Se), we find that Dirac surface states with a hexagonal warping term carry shift current by linearly polarized light. In addition, shift spin-current is introduced with the time-reversal symmetry breaking perturbation. The estimate for the mag…
Pure Spin Bulk Photovoltaic Effect in an Altermagnetic Higher-Order Topological Insulator
研究PT对称二维异质结构中体光伏效应，开发非阿贝尔公式描述其对称简并能带。发现奈尔矢量方向控制拓扑相和光学响应，该结构可产生纯自旋光电流，揭示非线性自旋输运对拓扑和磁对称性的探测作用。
Charge carriers in Dirac/Weyl semi-metals exhibit a relativistic-like behavior. In this work we propose a novel type of intrinsic half-integer Quantum Hall effect in 2D materials, thereby also offering a topological protection mechanism for the current. Its existence is rooted in the 2D parity anomaly, without any need for a perpendicular magnetic field. We conjecture that it may occur in disturbed honeycomb lattices where both spin degeneracy and time reversal symmetry are broken. These configurations harbor two distinct gap-opening mechanisms that, when occurring simultaneously, drive slight…
Topological phases and their topological features are enriched by the fundamental time-reversal, particle-hole, and chiral as well as crystalline symmetries. While one-dimensional (1D) generalized Su-Schrieffer-Heeger (SSH) systems show various topological phenomena such as topological solitons and topological charge pumping, it remains unclear how such symmetry protects and relates such topological phenomena. Here we show that the generalized time-reversal, particle-hole, and chiral symmetry operators consistently explain not only the symmetry transformation properties between the ground stat…
Numerical simulations of magnetization reversal of a quantum uniaxial magnet under a swept magnetic field [Hatomura, \textit{et al}., \textit{Quantum Stoner-Wohlfarth Model}, Phys. Rev. Lett. \textbf{116}, 037203 (2016)] are extended. In particular, how the "wave packet" describing the time-evolution of the system is scattered in the successive avoided level crossings is investigated from the viewpoint of the distribution of the eigenstate populations. It is found that the peak of the distribution as a function of the magnetic field does not depend on spin-size $S$, which indicates that the de…
When Screening Current Controls Ferroelectric Switching: From Field-Limited to Current-Limited Regimes
本文通过实验和模拟揭示，在扫描探针下铁电翻转受屏蔽电流供应和再分布速率限制，提出屏蔽电流限制机制，并解释纳米尺度压电滞回测量中畴壁定律的失效，将电流调控作为确定性纳米畴工程的手段。
Using the Keldysh technique, we derive a set of quasiclassical equations for Bloch electrons in noncentrosymmetric crystals upon excitation with quasimonochromatic radiation in the presence of external electrical and magnetic fields. These equations are the analog to the semiconductor-Bloch-equations for the dynamics of electrons including the photogalvanic effect (PGE) in particular the shift mechanism. The shift PGE was recently identified as showing promise for the development of new photovoltaic materials. In addition, our theory may be useful to investigate the interplay between breaking …
Band inversion, one of the key signatures of time-reversal invariant topological insulators (TIs), arises mostly due to the spin-orbit (SO) coupling. Here, based on ab initio density-functional calculations, we report a theoretical investigation of the SO-driven band inversion in isostructural bismuth and antimony chalcogenide TIs from the viewpoint of its interplay with the crystal-field effect. We calculate the SO-induced energy shift of states in the top valence and bottom conduction manifolds and reproduce this behavior using a simple one-atom model adjusted to incorporate the crystal-fiel…
Quantum wires subject to the combined action of spin-orbit and Zeeman coupling in the presence of \emph{s}-wave pairing potentials (superconducting proximity effect in semiconductors or superfluidity in cold atoms) are one of the most promising systems for the developing of topological phases hosting Majorana fermions. The breaking of time-reversal symmetry is essential for the appearance of unpaired Majorana fermions. By implementing a \emph{time-dependent} spin rotation, we show that the standard magnetostatic model maps into a \emph{non-magnetic} one where the breaking of time-reversal symm…
An ultra-strong photovoltaic effect has recently been reported for electrons trapped on a liquid Helium surface under a microwave excitation tuned at intersubband resonance [D. Konstantinov et. al. : J. Phys. Soc. Jpn. 81, 093601 (2012) ]. In this article, we analyze theoretically the redistribution of the electron density induced by an overheating of the surface electrons under irradiation, and obtain quantitative predictions for the photocurrent dependence on the effective electron temperature and confinement voltages. We show that the photo-current can change sign as a function of the param…
Despite the unsettled mechanism of electricity generation from the continuous flow of liquids on a surface, the charge-discharge theory has been widely accepted for alternating current (AC) generation from a moving droplet. It has been recently extended to rationalize direct current (DC) generation across a droplet moving between two different materials. By designing a reconfigurable contact between a metal wire and a water droplet moving on graphene, we show that the charge-discharge theory cannot explain the reversal of current when water-metal interfaces switch from dynamic to static. All e…
In this paper, by the use of the topological current theory, the topological structures and the dynamic processes in thin-film ferromagnetic systems are investigated directly from viewpoint of topology. It is found that the topological charge of a thin-film ferromagnetic system can be changed by annihilation or creation processes of opposite polarized vortex-antivortex pairs taking place at space-time singularities of the normalized magnetization vector field of the system, the variation of the topological charge is integer and can further be expressed in terms of the Hopf indices and Brouwer …
扫码添加微信好友，提出您的宝贵建议 👇
💡 备注请填写：网站反馈
发表机构由 AI 从论文文本抽取，如发现错误，欢迎反馈修正建议。