Observation of Peculiar Rashba-Type Spin-Split Band on Bi(111) Surface by High-Resolution Spin- and Angle-Resolved Photoemission Spectroscopy

Abstract

Spin polarized surface states of Bi(111) film fabricated on Si(111) surface have been investigated by means of high-resolution spin-resolved photoemission spectroscopy. In contrast to the Rashba-type spin-split ideal two-dimensional electron gas in which the spin orientation is locked in-plane and tangential to the electron momentum, significant out-of-plane spin polarization has been observed in the surface states which are forming the hole pocket. The out-of-plane spin polarization is anti-symmetric with respect to Γ-M line and vanishes at the line suggesting that the out-of-plane polarization is derived from the three-fold symmetry of the Bi crystal. The magnitude of the out-of-plane spin components depends on the condition of Bi film fabrication, which is consistent with the recent x-ray diffraction results suggesting the existence of double domains rotating 180° each other on the Bi(111) film grown on Si(111) surface. [DOI: 10.1380/ejssnt.2012.153]