Coherent Control of Topologically Protected Spin Currents

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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.