Chiral Quantum well Rashba splitting in Sb monolayer on Au(111)

We present a comprehensive investigation into the atomic and electronic structures of a single-layer Sb(110) rhombohedral crystal formed on an Au(111) substrate. Low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) reveal a pure two-dimensional (2D) Sb stripe structure, composed of a pair of Sb(110) unit cells located in a chiral configuration with mirror symmetry breaking perpendicular to the direction of the bright stripe. Based on angle-resolved photoemission spectroscopy (ARPES) measurements and Sb-weighted band structure from density functional theory calculations, we report the unambiguous determination of Rashba spin-orbit coupled bands from the 2D Sb film, exhibiting a chiral symmetry in the electronic structure with the crossing points located at the ${\Gamma}$ point and the X point, respectively. Moreover, From dI/dV spectra and density of states (DOS) calculations, the quantum well (QW) Rashba-type states induced by the in-plane mirror symmetry breaking in the Sb stripe structure have been identified. Orbital decomposition of the projected band structure reveals that hybridization between Sb py states and Au states modifies the spin splitting of the QW states, attributed to the intrinsic strong SOC of Au states introduced into the QW states.