Tuning Rashba spin-orbit coupling in homogeneous semiconductor nanowires

Paweł Wójcik,Andrea Bertoni,Guido Goldoni

doi:10.1103/physrevb.97.165401

Paweł Wójcik, Andrea Bertoni + Show 1 more

Open Access

https://doi.org/10.1103/physrevb.97.165401

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Abstract

We use $\vec{k}\cdot\vec{p}$ theory to estimate the Rashba spin-orbit coupling (SOC) in large semiconductor nanowires. We specifically investigate GaAs- and InSb-based devices with different gate configurations to control symmetry and localization of the electron charge density. We explore gate-controlled SOC for wires of different size and doping, and we show that in high carrier density SOC has a non-linear electric field susceptibility, due to large reshaping of the quantum states. We analyze recent experiments with InSb nanowires in light of our calculations. Good agreement is found with SOC coefficients reported in Phys. Rev.B 91, 201413(R) (2015), but not with the much larger values reported in Nat Commun., 8, 478 (2017). We discuss possible origins of this discrepancy.

Highlights

Semiconductor nanowires (NWs) are attracting increasing interest for electronic and optoelectronic applications, including single-photon sources [1], field effect transistors [2], photovoltaic cells [3], thermoelectric devices [4], lasers [5,6], and programmable circuits [7]
The electric field may arise from a symmetry breaking that is either intrinsic, i.e., related to the crystallographic structure of the material (Dresselhaus spin-orbit coupling (SOC)) [25], or induced by the overall asymmetry of the confinement potential due to an electrostatic field, due to, e.g., compositional profiles, strain, or external gates (Rashba SOC) [26]
SOC is the combination of both components [27], but zinc-blende NWs grown along [111] posses inversion symmetry, and the Dresselhaus contribution vanishes

Summary

INTRODUCTION

Semiconductor nanowires (NWs) are attracting increasing interest for (ultrafast) electronic and optoelectronic applications, including single-photon sources [1], field effect transistors [2], photovoltaic cells [3], thermoelectric devices [4], lasers [5,6], and programmable circuits [7]. Due to strong spinorbit coupling (SOC) in InSb- or InAs-based NWs, a helical gap has been observed if a finite magnetic field is applied orthogonal to the SOC effective field, BSOC [12,13,14,15,16] In this 1D state, carriers with opposite momentum have opposite spin. The standard method to extract the SOC in semiconductor NWs is by magnetoconductance measurements in low magnetic fields, exploiting the negative magnetoresistance due to weak antilocalization [32,33] This technique was used to extract SO strength in InSb NWs demonstrating very large values of the SOC constant, αR = 50–100 meV nm [34].

THEORETICAL MODEL

Effective Hamiltonian for SOC of conduction electrons

RESULTS

Computation of SO coupling constants

SUMMARY