Ultra-thin topological insulator spin-current transistor

拓扑绝缘体是现有的一类带隙绝缘体，同时它们确实通过它们的边缘（或在三维材料的情况下的表面）进行传导。由于材料独特的能带结构与强自旋轨道耦合，这些无带隙金属表面态自然产生螺旋极化自旋纹理。此外，由于反向散射的禁止，这些状态仅受到时间反演对称性的保护，并且在材料的边缘（表面）实现几乎无耗散的纯自旋电流（无净电荷电流）。基于拓扑绝缘体的自旋电流器件节省能量，因为它需要在边缘（表面）而不是在体中流动的小电流来访问它们的表面特性。 在本计画中，我们将利用利兹新的多重沈积系统，在真空中以分子束磊晶成长出超薄拓扑绝缘体Bi_（2-x）Sb_xTe_3与GeTe（Weyl半金属候选者）薄膜，以制作自旋电流场效电晶体。拓扑绝缘体（拓扑Weyl半金属）中存在无隙态是其特有的特性之一，但我们将通过采用超薄膜在表面态中打开间隙，其中顶部和底部表面态由于两者之间的干涉而变得不稳定。带隙表面态与门控技术将为我们提供一种制造自旋电流场效应晶体管的能力，可以打开/关闭的自旋极化电流。我们还将继续关注适用于该器件项目的其他拓扑绝缘体材料。 这是一个令人兴奋和非常活跃的研究领域的项目，使我们能够与利兹大学的其他研究团队密切互动和合作，包括理论小组。我们正在寻找一位有物理学、物理化学或材料科学背景的积极进取的学生

Topological insulators are an existing class of band-gap insulators, whilst they do conduct through their edge (or the surface in the case of 3 dimensional materials). These gapless metallic surface states are naturally generated with helically polarized spin texture due to strong spin-orbit coupling with a peculiar energy band structure of materials. Moreover, the states are protected by time-reversal symmetry simply due to prohibition of back scattering and realize almost dissipation-less pure spin currents (no net charge current) at the edge (surface) of materials. Spin-current devices based on the topological insulators save energy because it requires small current that flow at the edge (the surface) not in the bulk to access their surface properties. In this project, we will fabricate a spin-current field effect transistor with an ultra-thin topological insulator Bi2-xSbxTe3 and GeTe (a Weyl semimetal candidate) films grown by molecular beam epitaxy in ultrahigh vacuum, a part of a new multi-deposition system in Leeds. Existence of gapless states in topological insulators (topological Weyl semimetals) are one of peculiar characteristics but we will open a gap in the surface state by employing ultra-thin films where the top and bottom surface states get unstable due to an interference between two. The gapped surface state with a gating technique will provide us a capability of fabricating a spin-current filed effect transistor that can switch on/off the spin-polarized current. We will also keep our eye on other topological insulator materials suitable for this device project. This is a project in an exciting and very active research area which allows us to closely interact and collaborate with other research teams in the University of Leeds including a theoretical group. We are looking for a motivated student with a background in physics, physical chemistry, or material science