Ultra-thin topological insulator spin-current transistor

拓扑绝缘体是一种现有的带隙绝缘体，虽然它们确实通过它们的边缘（或三维材料的表面）导电。由于材料的特殊能带结构与强自旋轨道耦合，这些无间隙的金属表面态自然产生了螺旋极化的自旋织构。此外，由于禁止反向散射，这些状态受到时间反转对称性的保护，并在材料的边缘（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了能量，因为它需要在边缘（表面）流动的小电流，而不是在大块中流动，以获得其表面特性。在这个项目中，我们将用超薄拓扑绝缘体Bi2-xSbxTe3和在超高真空中通过分子束外延生长的GeTe （Weyl半金属候选物）薄膜制造自旋电流场效应晶体管，这是利兹大学新的多层沉积系统的一部分。拓扑绝缘体（拓扑Weyl半金属）中存在无间隙态是其独特的特性之一，但我们将通过使用超薄薄膜在表面状态中打开一个间隙，其中顶部和底部表面状态由于两者之间的干扰而变得不稳定。采用门控技术的间隙表面态将为我们提供制造自旋电流场效应晶体管的能力，该晶体管可以开关自旋极化电流。我们也将继续关注其他适合该器件项目的拓扑绝缘体材料。这是一个令人兴奋和非常活跃的研究领域的项目，它使我们能够与利兹大学的其他研究团队密切互动和合作，包括一个理论小组。我们正在寻找具有物理，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