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Topologically Entangled Rashba-Split Shockley States on the Surface of Grey Arsenic
Peng Zhang1,2, J-Z Ma2, Y Ishida1
1Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
Abstract:
We discover a pair of spin-polarized surface bands on the (111) face of grey arsenic by using angle-resolved photoemission spectroscopy (ARPES). In the occupied side, the pair resembles typical nearly-free-electron Shockley states observed on noble-metal surfaces. However, pump-probe ARPES reveals that the spin-polarized pair traverses the bulk band gap and that the crossing of the pair at Γ[over ¯] is topologically unavoidable. First-principles calculations well reproduce the bands and their nontrivial topology; the calculations also support that the surface states are of Shockley type because they arise from a band inversion caused by crystal field. The results provide compelling evidence that topological Shockley states are realized on As(111).
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