Topologically entangled Rashba-split Shockley states on the surface of grey arsenic
ORAL
Abstract
Topological surface states (SSs) and Shockley SSs are two kinds of typical SSs. The relationship between them has been theoretically proposed while convincing experimental evidence is still absent. Here 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 $\Gamma $ is topologically unavoidable. First-principles calculations well reproduce the bands and their non-trivial topology; it also supports 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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