Studies of spin-polarized surface states by laser-based time-resolved ARPES and spin-resolved ARPES

   We have been studying spin-polarized surface states by using laser-based time-resolved angle-resolved photoemission spectroscopy (Tr-ARPES), and spin-resolved ARPES (SARPES). For an intrinsic three-dimensional topological insulator, Bi1.5Sb0.5Te1.7Se1.3, we clarified suppression of electron backscattering in a helically spin-polarized surface state in combination with quasi-particle interference detection using scanning tunneling spectroscopy.[1] We have further investigated the electron dynamics of the surface electrons by Tr-ARPES. Recently, we have developed laser-based SARPES with twin spin detectors of a very-low-energy-electron-diffraction type for the 3-dimensional measurements of the spin direction. We have measured spin-polarized surface states for several systems including Bi(111) and a Weyl semimetal.[2]

1.S. Kim et. al., Phys. Rev. Lett. 112, 136802 (2014).

2.2. S.-Y. Xu et. al., arXiv preprint arXiv:1510.08430 (2015).