Terahertz spin- and valleytronics

自旋和谷指数代表了一类二维材料中准粒子的关键量子标记，是自旋电子学和谷电子学领域的基本元素。虽然已经确定超快光脉冲可以控制谷的电荷状态，但控制谷和自旋电流的大小和方向的可靠协议仍然是一个寻求的目标。通过将太赫兹调制包层与电荷激发脉冲相结合的定制混合光脉冲，我们旨在展示光控制各种材料中自旋电流和谷电流的产生：二维磁体CrI3和Fe3GeTe2中的自旋电流以及六方BN （hBN）和单层石墨烯异质结构中的谷电流。后一系统将为探测相干电流产生中的云纹效应提供一个平台，而二维磁体CrI3和TMDCs的异质结构将作为一个可以通过调谐脉冲参数选择性激发几层堆栈中的层自由度的系统进行研究。这项工作分为三个工作包：（WP） WP1：建立（太赫兹）导频和激励组件的混合光脉冲如何在二维磁体中产生受控的自旋光电流。两种磁体目前的实验兴趣将考虑：CrI3和Fe3GeTe2。在这个工作包中，将建立和测试项目其余部分的方法，最重要的是，将建立与从头算时相关密度泛函理论（TD-DFT）相比，万尼化紧密结合的准确性。WP2：六方氮化硼和石墨烯云纹中谷光电流的产生，基于在最小间隙理想石墨烯中建立光电流响应的初步工作。一个关键问题是确定由光引起的谷电流的云纹效应：云纹在光电流上的印记是什么？WP3：二维磁体和TMDC异质结构中产生自旋和谷光电流的裁剪脉冲。这里的核心问题将是如何调整脉冲参数来控制异质结构不同层中的层间和层内电流。

Spin and valley indices represent the key quantum labels of quasi-particles in a wide class of two dimensional materials, and form the foundational elements of the fields of spintronics and valleytronics. While it is well established that ultrafast light pulses can control the charge state of a valley, robust protocols for control over the magnitude and direction of valley and spin-currents remains a sought for goal. By employing tailored hybrid light pulses combining THz modulating envelopes with charge excitation pulses we aim to demonstrate light control over the generation of spin and valley currents in a wide range of materials: spin currents in the 2d magnets CrI3 and Fe3GeTe2 and valley currents heterostructures of hexagonal BN (hBN) and single layer graphene. The latter system will provide a platform for probing moire effects in coherent current generation, while heterostructures of the 2d magnet CrI3 and TMDCs will be investigated as a system for which the layer freedom in a few layer stack can be selectively excited by tuning pulse parameters. The work is divided into three work packages :(WP) WP1: Establish how hybrid light pulses of (THz) pilot and excitation components can generate controlled spin photocurrents in 2d magnets. Two magnets of current experimental interest will be considered: CrI3 and Fe3GeTe2. In this work-package methodologies for the rest of the project will be established and tested, most importantly the accuracy of a Wannierized tight-binding as compared to ab-initio time-dependent density functional theory (TD-DFT) will be established. WP2: Generation of valley photocurrents in moires of hexagonal Boron Nitride and graphene, building on preliminary work establishing a photocurrent response in minimally gapped ideal graphene. A key question is the determination of moire effects on valley currents induced by light: what is the imprint of the moire on the photocurrent? WP3: Tailoring pulses for the generation of spin and valley photocurrents in heterostructures of 2d magnets and TMDC. The central question here will be how pulse parameters can be tuned to control both interlayer and intralayer current in the distinct layers of the heterostructure.