Coherent Control of Topologically Protected Spin Currents

这项提议是为了购买一个用于在红外中产生可调谐相干光子的光学参数放大器、一个近红外光谱仪和一些额外的关键光学部件。这一新设备将补充达马塞利、琼斯和萨瓦茨基在哥伦比亚大学量子材料实验室建立的角度、自旋和时间分辨光电子能谱的世界级基础设施，并使我们能够开发一种新的实验技术，用于相干控制自旋极化电流，被广泛认为是自旋电子学领域的圣杯。 我们的研究重点是理解、控制和开发量子材料的磁性和电学性质，其中拓扑绝缘体-由于存在自旋极化和拓扑保护的表面态(TSS)-具有巨大的自旋电子应用前景。我们已经在理论和实验水平上成功地探索了典型的拓扑绝缘体Bi2Se_3的轨道和磁性织构。获得完全自旋极化控制的下一步是开发技术，使我们能够填充和连贯地控制TSS的占据，进而产生和操纵自旋极化电流。 为此，我们最近发现了一条新的途径，基于可调的双色光激发方案，实现了对拓扑绝缘体中拓扑保护的自旋电流的相干控制。然而，该实验室缺少实现正确条件所需的关键设备，在这种条件下可以产生这种自旋极化电流-并最终通过我们最先进的基础设施进行可视化。将后者与所需的设备相结合，我们的目标是首次在实验上演示TSS占据和相关自旋极化电流的相干控制。

This proposal is for the purchase of an Optical Parametric Amplifier for the generation of tunable coherent photons in the infrared, a Near Infrared Spectrometer, and a few additional key optical components. This new equipment will complement the world-class infrastructure for angle-, spin-, and time-resolved photoelectron spectroscopy established by Damascelli, Jones, and Sawatzky in the Quantum Materials Laboratory at UBC, and enable us to develop a novel experimental technique for the coherent control of spin-polarized currents, broadly considered to be the holy grail in the field of spintronics. The focus of our research effort is the understanding, control, and exploitation of the magnetic and electronic properties of quantum materials, and among them topological insulators which - owing to the presence of a spin-polarized and topologically-protected surface state (TSS) - hold great promise for spintronic applications. We have already successfully explored, at both theoretical and experimental level, the orbital and magnetic texture of the archetypical topological insulator Bi2Se3. The next step towards gaining full spin-polarization control is to develop techniques that will allow us to populate and coherently control the occupation of the TSS, and in turn generate and manipulate spin-polarized electrical currents. To this end, we have recently identified a new pathway towards achieving coherent control of topologically protected spin currents in topological insulators, based on the utilization of a tunable two-color photoexcitation scheme. However, the laboratory is missing key equipment needed to achieve the correct conditions under which this spin-polarized current can be generated - and eventually visualized with our state-of-the-art infrastructure. Combining the latter with the requested equipment, we aim to experimentally demonstrate - for the fist time - the coherent control of the TSS occupation and of the associated spin-polarized currents.