Strongly anisotropic spin-orbit splitting in a two-dimensional electron gas

TY - JOUR

T1 - Strongly anisotropic spin-orbit splitting in a two-dimensional electron gas

AU - Michiardi, Matteo

AU - Bianchi, Marco

AU - Dendzik, Maciej

AU - Miwa, Jill

AU - Hoesch, Moritz

AU - Kim, Timur K.

AU - Matzen, Peter

AU - Mi, Jianli

AU - Bremholm, Martin

AU - Iversen, Bo Brummerstedt

AU - Hofmann, Philip

PY - 2015

Y1 - 2015

N2 - Near-surface two-dimensional electron gases on the topological insulator Bi$_2$Te$_2$Se are induced by electron doping and studied by angle-resolved photoemission spectroscopy. A pronounced spin-orbit splitting is observed for these states. The $k$-dependent splitting is strongly anisotropic to a degree where a large splitting ($\approx 0.06$ \AA$^{-1}$) can be found in the $\bar{\Gamma}\bar{M}$ direction while the states are hardly split along $\bar{\Gamma}\bar{K}$. The direction of the anisotropy is found to be qualitatively inconsistent with results expected for a third-order anisotropic Rashba Hamiltonian. However, a $\mathbf{k} \cdot \mathbf{p}$ model that includes the possibility of band structure anisotropy as well as both isotropic and anisotropic third order Rashba splitting can explain the results. The isotropic third order contribution to the Rashba Hamiltonian is found to be negative, reducing the energy splitting at high $k$. The interplay of band structure, higher order Rashba effect and tuneable doping offers the opportunity to engineer not only the size of the spin-orbit splitting but also its direction.

AB - Near-surface two-dimensional electron gases on the topological insulator Bi$_2$Te$_2$Se are induced by electron doping and studied by angle-resolved photoemission spectroscopy. A pronounced spin-orbit splitting is observed for these states. The $k$-dependent splitting is strongly anisotropic to a degree where a large splitting ($\approx 0.06$ \AA$^{-1}$) can be found in the $\bar{\Gamma}\bar{M}$ direction while the states are hardly split along $\bar{\Gamma}\bar{K}$. The direction of the anisotropy is found to be qualitatively inconsistent with results expected for a third-order anisotropic Rashba Hamiltonian. However, a $\mathbf{k} \cdot \mathbf{p}$ model that includes the possibility of band structure anisotropy as well as both isotropic and anisotropic third order Rashba splitting can explain the results. The isotropic third order contribution to the Rashba Hamiltonian is found to be negative, reducing the energy splitting at high $k$. The interplay of band structure, higher order Rashba effect and tuneable doping offers the opportunity to engineer not only the size of the spin-orbit splitting but also its direction.

KW - cond-mat.str-el

KW - cond-mat.mes-hall

U2 - 10.1103/PhysRevB.91.035445

DO - 10.1103/PhysRevB.91.035445

M3 - Tidsskriftartikel

SN - 0163-1829

VL - 91

JO - Physical Review B Condensed Matter

JF - Physical Review B Condensed Matter

M1 - 035445

ER -