Quantum spin Hall effect spintronics

量子自旋霍尔效应自旋电子学

基本信息

批准号：
EP/T034343/1
负责人：
Christopher Marrows
金额：
$ 109.82万
依托单位：
University of Leeds
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2021
资助国家：
英国
起止时间：
2021 至无数据
项目状态：
未结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FT034343%2F1
关键词：
Quantum spin Hall effect spintronics

项目摘要

In this project we shall investigate the potential for spintronics of the quantum spin Hall (QSH) regime in hybrid nanostructures made by attaching ferromagnetic metal contacts to the edge states of two-dimensional topological insulators. These 2D materials will be formed from semiconducting InAs/GaSb coupled quantum wells. Being able to harness the spin-momentum-locked helical edge states in the QSH regime will have the potential for realising dramatic reductions in the power consumption of classical ICT hardware, and in the longer term offer the prospect of being useful for topological quantum computing. To build such spintronic devices, we need to know the conditions under which current flows through their edge states. We need to know the spin polarisation of a current injected from a ferromagnet into the QSH edge state, and which ferromagnetic contact material provides the largest spin-polarisation. We need to know how efficiently spins can be injected and detected in these QSH edge channels using ferromagnetic metal contacts. We also need to know over what distance spin information can propagate in the QSH edge states, and in what circumstances this distance is the longest.The project is a collaboration between the School of Physics and Astronomy, who have expertise in spintronics and the study of devices incorporating ferromagnetic materials, as well as topological materials, and the School of Electronic and Electrical Engineering, who are capable of growing ultra-high quality InAs/GaSb coupled quantum wells in their III-V semiconductor molecular beam epitaxy system. We will begin by constructing contacted InAs/GaSb mesas with top and bottom gates that allow them to be tuned into a charge-neutral and non-trivial regime, which are the correct conditions for current to flow only in the edge states. We will attach normal drain contacts on either side of a ferromagnetic source contact on a InAs/GaSb mesa and measure the drain currents from left- and right-flowing edge states in the non-trivial edge state regime; the spin-momentum locking in the QSH edge states will mean that these spatially separated currents directly correspond to the spin-resolved currents, allowing a direct measurement of the spin-polarisation of the current injected from the ferromagnet. We shall try different ferromagnetic metals to determine which one works best. We will then study the flow of a current in a QSH edge state between two closely-spaced ferromagnetic contacts, which is expected to be larger when the current flow direction is spin-momentum locked to the majority spin direction of the contacts; reversing the magnetisation direction in the contacts will invert this diode-like behaviour. The difference between forward and reverse currents will tell us the efficiency of the spin injection and detection. Moving the contacts apart will allow us to determine the length over which spins can flow coherently within the edge states by measuring the decline in difference between forward and reverse currents with spacing; we shall study this as a function of temperature in order to determine the physical mechanisms causing the loss of spin coherence. The results we shall obtain will not only lead to high impact publications and conference presentations by shedding light on the possibilities offered by this novel combination of materials, but also develop valuable know-how in the field of quantum spin Hall spintronics for technological applications.

在这个项目中，我们将研究通过将铁磁金属触点连接到二维拓扑绝缘子的边缘状态的混合纳米结构中量子旋转大厅（QSH）体制的潜力。这些2D材料将是由半导体INAS/GASB耦合量子井形成的。能够利用QSH政权中的旋转摩托杆锁的螺旋边缘状态将有可能实现经典ICT硬件的功耗急剧减少，从而长期提供了对拓扑量子计算有用的前景。要构建此类自旋设备，我们需要知道电流通过其边缘状态的条件。我们需要知道从铁磁体注入QSH边缘状态的电流的自旋极化，哪种铁磁接触材料提供了最大的自旋化。我们需要知道如何使用铁磁金属触点在这些QSH边缘通道中注入和检测到如何有效地注入和检测到。我们还需要了解QSH边缘状态下哪些距离旋转信息可以传播的，并且在什么情况下，该项目是最长的。 III-V半导体分子束外延系统。我们将首先构建具有顶部和底部大门的接触INAS/GASB台面，使它们可以将其调整为电荷中性和非平凡的状态，这是当前仅在边缘状态下流动的正确条件。我们将在INAS/GASB MESA上的铁磁源接触的两侧附加正常的排水接触，并在非平凡边缘状态状态下的左和右边缘状态测量排水电流； QSH边缘状态中的自旋摩托锁定将意味着这些空间分离的电流直接对应于自旋分辨电流，从而可以直接测量从铁磁体注入的电流的自旋化。我们将尝试不同的铁磁金属来确定哪种作用最佳。然后，我们将研究两个紧密间隔的铁磁触点之间的QSH边缘状态下的电流流动，当电流流动方向锁定到触点的多数自旋方向时，预计会更大。逆转触点中的磁化方向将颠倒这种类似二极管的行为。正向电流和反向电流之间的差异将告诉我们自旋注射和检测的效率。将触点分开将使我们能够通过测量旋转在边缘状态中连贯流动的长度，通过测量向前和反向电流之间的差异下降；我们将研究这是温度的函数，以确定导致旋转相干性丧失的物理机制。我们将获得的结果不仅会通过阐明这种新型材料组合所提供的可能性，还会导致高影响出版物和会议演讲，而且还可以在量子旋转霍尔纺纱型领域开发出宝贵的知识，以用于技术应用。