Spin Configuration and Scattering Rates on the Heavily Electron-doped Surface of Topological Insulator Bi$_2$Se$_3$

TL;DR

This study investigates the spin configurations and scattering mechanisms on heavily electron-doped Bi$_2$Se$_3$ surfaces, revealing Rashba-type spin splitting, alternating spin helicities, and dominant intra-band scattering influenced by Fermi surface warping.

Contribution

It provides detailed spin-resolved measurements of doped Bi$_2$Se$_3$, demonstrating Rashba splitting and analyzing how spin configurations affect scattering channels.

Findings

Rashba-type spin splitting observed due to large spin-orbit coupling.

Alternating spin helicities in Rashba doublet and topological surface state.

Intra-band scattering dominates, influenced by Fermi surface warping.

Abstract

Heavily electron-doped surfaces of Bi$_2$Se$_3$ have been studied by spin and angle resolved photoemission spectroscopy. Upon doping, electrons occupy a series of {\bf k}-split pairs of states above the topological surface state. The {\bf k}-splitting originates from the large spin-orbit coupling and results in a Rashba-type behavior, unequivocally demonstrated here via the spin analysis. The spin helicities of the lowest laying Rashba doublet and the adjacent topological surface state alternate in a left-right-left sequence. This spin configuration sets constraints to inter-band scattering channels opened by electron doping. A detailed analysis of the scattering rates suggests that intra-band scattering dominates with the largest effect coming from warping of the Fermi surface.