谷层耦合二维材料中的非常规线性横向激子输运
Unconventional linear transverse exciton transport in valley-layer coupling two-dimensional materials
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中文总结 AI 辅助
本研究提出谷层耦合二维材料中由垂直电场调控的非常规线性横向激子输运，揭示单层与扭曲双层中的各向异性机制，为激子输运控制提供新途径。
中文摘要 AI 辅助
谷层耦合（VLC）二维（2D）材料定义了一类独特的量子系统，其中谷由晶体对称性而非时间反演（$\mathcal{T}$）对称性相关联，从而实现了栅极控制的谷对比层极化。在此，我们将这一概念扩展到激子。以TiSiCo作为原型VLC材料，我们展示了垂直电场$E_{\perp}$控制激子色散的各向异性，从而在单层和扭曲双层结构中产生非常规的线性横向激子输运。在单层中，该响应由各向异性诱导的横向电导率表征，这些电导率源于电导率张量对角元反对称组合，并可通过$E_{\perp}$强烈调节。在扭曲双层中，对称性还允许来自电导率张量对称部分的横向响应。由于不同层内的层内激子通过Förster耦合相连，这些对称和反对称响应共存并与最近提出的$\mathcal{T}$偶层霍尔和能斯特激子反向流竞争。这种相互作用可通过扭曲角、温度和面内驱动力方向高度调节，为实验上区分不同的横向激子输运信号提供了途径。我们的结果确立了$E_{\perp}$作为通过VLC控制激子输运的强大旋钮，并将VLC二维材料确定为工程化激子现象的有前景平台。
英文摘要
Valley-layer coupling (VLC) two-dimensional (2D) materials define a distinct class of quantum systems in which valleys are related by crystal, rather than time-reversal ($\mathcal{T}$) symmetry, enabling gate-controlled valley-contrasted layer polarization. Here we extend this concept to excitons. Using TiSiCo as a prototype VLC material, we show that a perpendicular electric field $E_{\perp}$ controls exciton- dispersion anisotropy and thereby generates unconventional linear transverse exciton transport in both monolayer and twisted bilayer structures. In the monolayer, this response is characterized by anisotropy-induced transverse conductivities, arising from the antisymmetric combination of diagonal elements in the conductivity tensor and strongly tunable by $E_{\perp}$. In the twisted bilayer, symmetry additionally permits transverse responses from the symmetric part of the conductivity tensor. Since intralayer excitons in different layers are connected by the Förster coupling, these symmetric and antisymmetric responses coexist and compete with the recently proposed $\mathcal{T}$-even layer Hall and Nernst exciton counterflow. This interplay is highly tunable by twisted angle, temperature, and the direction of the in-plane driving force, providing a route to disentangle distinct transverse exciton transport signals experimentally. Our results establish $E_{\perp}$ as a powerful knob for controlling exciton transport via VLC and identify VLC 2D materials as a promising platform for engineered excitonic phenomena.
发表机构
- School of Physics and Electronics, Hunan University（湖南大学物理与电子学院）
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