Erin Fleck, Stanford University

Probing spin-orbit interactions near a topological phase transition using spin-ARPES

Angle-resolved photoemission spectroscopy (ARPES) is a powerful technique that enables the direct measurement of electronic band structure. Spin-resolved ARPES in addition directly probes the spin polarization of photoemitted electrons, providing deeper insight into the underlying physics of these materials, though the intrinsic inefficiency of spin detection has proven to be a significant barrier to harnessing the full power of this technique. Recent progress in creating increasingly efficient methods of spin detection have thus stimulated a wealth of spin-ARPES measurements across a wide range of materials. Leveraging the increasing capability of this technique, we have performed high-resolution spin-ARPES measurements to observe the spin texture of a material on the threshold of a topological phase transition, ZrTe5. Our work reveals spin-polarized electronic bands as the material approaches a topological phase transition and offers new perspectives on how spin-orbit interactions manifest in the topological character of this material. We highlight strong light polarization dependence of the spin texture, which further evidences coupling between the spin and orbital degrees of freedom. Beyond the material of study, our results underscore the growing capabilities of spin-resolved ARPES and its potential to uncover novel spin-dependent phenomena in complex materials.