Spin-texture inversion in the giant Rashba semiconductor BiTeI

Abstract

Semiconductors with strong spin–orbit interaction as the underlying mechanism for the generation of spin-polarized electrons are showing potential for applications in spintronic devices. Unveiling the full spin texture in momentum space for such materials and its relation to the microscopic structure of the electronic wave functions is experimentally challenging and yet essential for exploiting spin–orbit effects for spin manipulation. Here we employ a state-of-the-art photoelectron momentum microscope with a multichannel spin filter to directly image the spin texture of the layered polar semiconductor BiTeI within the full two-dimensional momentum plane. Our experimental results, supported by relativistic ab initio calculations, demonstrate that the valence and conduction band electrons in BiTeI have spin textures of opposite chirality and of pronounced orbital dependence beyond the standard Rashba model, the latter giving rise to strong optical selection-rule effects on the photoelectron spin polarization. These observations open avenues for spin-texture manipulation by atomic-layer and charge carrier control in polar semiconductors.

Direct mapping of spin and orbital entangled wave functions under interband spin-orbit coupling of giant Rashba spin-split surface states

“…This explains not only that the even-and odd-parity orbitals couple with opposite spins but also that the SO entanglement is a general consequence of the SO coupling. Indeed the similar SO-coupled states have been recently confirmed in surface states of topological insulators [34][35][36][37][38][39] and Rashba states in BiTeI [40,41].…”

Rashba-like spin splitting along three momentum directions in trigonal layered PtBi2

“…Many phenomena related to Rashba-type SOC have been studied in a variety of systems . In particular, BiTeI and GeTe gained attention for their giant Rashba splitting in bulk states [35][36][37][38][39][40][41][42][43][44][45]. However, in all known instances, the Rashba bands remain spin degenerate along out-of-plane direction k z for k x = k y = 0, while they show spin splitting along the in-plane momentum directions, namely, k x and k y directions.…”

Strong Linear Dichroism in Spin-Polarized Photoemission from Spin-Orbit-Coupled Surface States

“…At the same time, the efficiency of stateof-the-art photoelectron spin detectors has been improved tremendously [11,16,17], making it now possible to measure the photoelectron spin polarization over wide regions of momentum space with varying energy and polarization of the exciting light. Despite these encouraging developments fundamental issues remain debated, namely to which degree, under which conditions, and in which way the measured photoelectron spin polarization actually reflects the intrinsic spin properties of spin-orbit split states [11,[18][19][20][21][22][23][24][25][26].Within the one-step theory of photoemission the spindependent photocurrent is determined by the photoemission matrix element which involves the initial state of the transition -the object of interest -and the final state of the outgoing photoelectron. In the vacuum ultraviolet photonenergy regime, commonly used in spin-ARPES experiments, the properties of the final state may quickly vary with the excitation energy and deviate considerably from the naive assumption of a free-electron state [27].…”

“…At the same time, the efficiency of stateof-the-art photoelectron spin detectors has been improved tremendously [11,16,17], making it now possible to measure the photoelectron spin polarization over wide regions of momentum space with varying energy and polarization of the exciting light. Despite these encouraging developments fundamental issues remain debated, namely to which degree, under which conditions, and in which way the measured photoelectron spin polarization actually reflects the intrinsic spin properties of spin-orbit split states [11,[18][19][20][21][22][23][24][25][26].…”