Giant Rashba spin splitting induced by heavy element adsorption at germanene

Abstract

Density functional theory calculations have been performed to investigate the structural and electronic properties of the Pb@germanene adsorption system. By employing equilibrium ab initio atomistic thermodynamics and phonon spectra analysis a dynamically stable configuration have been found. It is a (1 × 1) structure with coverage of 1 monolayer [(1×1)′@germanene]. The surface configuration shares some structural similarities with the sTable (1 × 1) phase of Pb@Ge(111), however, it favors a different adsorption site, and facilitates more Pb–Ge bonds per adsorbed atom. This results in (1×1)′@germanene having lower surface free energy than its Ge(111) counterpart. The electronics have been investigate using both GGA-type PBE and hybrid HSE functionals in order to ensure the accuracy. In both cases the system is a metal. Strong spin-orbit interaction of electrons in Pb facilitates a giant spin splitting of metallic bands up to 646 meV at the Fermi level, which makes the system an interesting platform for two-dimensional spintronics.