Terahertz spin- and valleytronics

自旋和谷指数代表了二维材料中准粒子的关键量子标签，并形成了自旋电子学和谷电子学领域的基础元素。虽然已经确定超快光脉冲可以控制谷的电荷状态，但是用于控制谷和自旋电流的幅度和方向的鲁棒协议仍然是寻求的目标。通过采用定制的混合光脉冲相结合的太赫兹调制信封与电荷激发脉冲，我们的目标是证明光控制的自旋和谷电流的产生在广泛的材料：自旋电流在2D磁铁CrI 3和Fe 3GeTe 2和谷电流异质结构的六方BN（hBN）和单层石墨烯。后者的系统将提供一个平台，用于探测相干电流产生的莫尔效应，而异质结构的2D磁体CrI 3和TMDC将作为一个系统进行研究，在几个层堆叠的层自由度可以选择性地激发通过调整脉冲参数。这项工作分为三个工作包：（WP）WP 1：建立（THz）先导和激励组件的混合光脉冲如何在2D磁体中产生受控的自旋光电流。将考虑目前实验感兴趣的两种磁体：CrI 3和Fe 3GeTe 2。在本工作包中，将建立和测试项目其余部分的方法，最重要的是，将建立与从头算含时密度泛函理论（TD-DFT）相比的Wannierized紧束缚的准确性。WP 2：在六方氮化硼和石墨烯的波纹中产生谷光电流，建立在建立最小间隙的理想石墨烯中的光电流响应的初步工作的基础上。一个关键的问题是由光引起的谷电流的莫尔效应的确定：什么是光电流上的莫尔条纹的印记？WP 3：定制脉冲，用于在2D磁体和TMDC的异质结构中产生自旋和谷光电流。这里的中心问题将是如何调整脉冲参数，以控制异质结构的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.