Bulk and surface Rashba splitting in single termination BiTeCl

Gabriel Landolt,Stefan Muff,Evgueni V Chulkov,Jürg Osterwalder,Bartosz Slomski,Masaki Kobayashi,Vladimir N Strocov,Thorsten Schmitt,Konstantin A Kokh,Oleg E Tereshchenko,Sergey V Eremeev,J Hugo Dil

doi:10.1088/1367-2630/15/8/085022

Abstract

By angle-resolved photoemission spectroscopy (ARPES) we observe a giant Rashba-type spin splitting in the electronic bulk conduction and valence bands of the semiconductor BiTeCl. This material belongs to the group of bismuth tellurohalides BiTeX (X = Cl,Br,I) which are layered non-centrosymmetric materials with strong spin–orbit interaction. By photon energy-dependent ARPES, we separate the bulk and surface contribution of the electronic structure and show that the tellurium-terminated (0001) crystal surface hosts spin-split two-dimensional surface states. On the chlorine-terminated surface at the opposite side of the crystal no surface states are observed due to photon-induced surface chemistry.

Highlights

Μ kx macroscopic scale with well-defined surface terminations
We argue that a chemical process at the chlorine surface induced by the intense synchrotron photon beam is the reason for the reduced size of the band bending and the absence of surface states on the chlorine termination
We suggest that the states are destroyed by the photon beam which significantly changes the surface chemistry

Summary

Introduction

Μ kx macroscopic scale (mm) with well-defined surface terminations. A preserved stacking order along the polar axis is indispensable for transport measurements since spin effects would cancel out in systems with a mixed orientation of quantization axes. BiTeCl has a hexagonal crystal structure (space group C64v) of alternating layers of chlorine, bismuth and tellurium atoms as illustrated in figure 1(a) [11]. The crystal has no inversion symmetry due to the continuous stacking order of the three atomic layers. In contrast to BiTeI and BiTeBr, the unit cell of BiTeCl is doubled in the c-direction in such a way that the crystal is symmetric under the screw operation composed of a non-primitive translation by c/2 along the hexagonal axis and a rotation of π/3 around the same axis. Owing to the lack of inversion symmetry, an ideal crystal can have two nonequivalent surfaces, with either Te- or Cl termination, determined by the underlying crystal stacking order. For our measurements care was taken to produce chemically pure terminations

Methods

Discussion

Conclusion