Rashba quantum wire: exact solution and ballistic transport

TL;DR

This paper provides an exact analytical solution for Rashba spin-orbit interaction in quantum wires, analyzing spectral and transport properties, and revealing spin polarization effects at interfaces within the ballistic regime.

Contribution

It offers an exact wave function solution and detailed transport analysis for Rashba quantum wires, including interface effects and comparison with simplified models.

Findings

Exact wave function and eigenvalues for Rashba quantum wires

Spin polarization occurs at interfaces with different spin-orbit strengths

Oscillations in spin polarization due to spin-selective bound states

Abstract

The effect of Rashba spin-orbit interaction in quantum wires with hard-wall boundaries is discussed. The exact wave function and eigenvalue equation are worked out pointing out the mixing between the spin and spatial parts. The spectral properties are also studied within the perturbation theory with respect to the strength of the spin-orbit interaction and diagonalization procedure. A comparison is done with the results of a simple model, the two-band model, that takes account only of the first two sub-bands of the wire. Finally, the transport properties within the ballistic regime are analytically calculated for the two-band model and through a tight-binding Green function for the entire system. Single and double interfaces separating regions with different strengths of spin-orbit interaction are analyzed injecting carriers into the first and the second sub-band. It is shown that in the case of a single interface the spin polarization in the Rashba region is different from zero, and in the case of two interfaces the spin polarization shows oscillations due to spin selective bound states.