Low-symmetry nanowire cross-sections for enhanced Dresselhaus spin-orbit interaction

TL;DR

This paper provides a theoretical analysis of the Dresselhaus spin-orbit interaction in low-symmetry nanowire cross-sections, highlighting configurations that enhance or suppress spin-orbit coupling for potential spintronic applications.

Contribution

It derives the effective Dresselhaus term for various nanowire orientations and cross-sections, offering detailed predictions for experimental setups and material combinations.

Findings

Certain configurations suppress Dresselhaus coupling at low symmetry.

Nanowire cross-sections like half-disks yield strong Dresselhaus interactions.

InAs and InSb nanowires can achieve millielectronvolt spin-orbit energies.

Abstract

We study theoretically the spin-orbit interaction of low-energy electrons in semiconducting nanowires with a zinc-blende lattice. The effective Dresselhaus term is derived for various growth directions, including <11(-2)>-oriented nanowires. While a specific configuration exists where the Dresselhaus spin-orbit coupling is suppressed even at confinement potentials of low symmetry, many configurations allow for a strong Dresselhaus coupling. In particular, we discuss qualitative and quantitative results for nanowire cross-sections modeled after sectors of rings or circles. The parameter dependence is analyzed in detail, enabling predictions for a large variety of setups. For example, we gain insight into the spin-orbit coupling in recently fabricated GaAs-InAs nanomembrane-nanowire structures. By combining the effective Dresselhaus and Rashba terms, we find that such structures are promising platforms for applications where an electrically controllable spin-orbit interaction is needed. If the nanowire cross-section is scaled down and InAs replaced by InSb, remarkably high Dresselhaus-based spin-orbit energies of the order of millielectronvolt are expected. A Rashba term that is similar to the effective Dresselhaus term can be induced via electric gates, providing means to switch the spin-orbit interaction on and off. By varying the central angle of the circular sector, we find, among other things, that particularly strong Dresselhaus couplings are possible when nanowire cross-sections resemble half-disks.