Quasiparticle velocities in 2D electron/hole liquids with spin-orbit coupling

TL;DR

This paper analyzes how spin-orbit interactions affect quasiparticle velocities in 2D electron and hole liquids, revealing significant effects in hole systems that can be observed experimentally.

Contribution

It provides analytical results for quasiparticle dispersions with isotropic spin-orbit interactions in high-density 2D liquids, extending known models to higher order and highlighting differences between electrons and holes.

Findings

Electron quasiparticle velocities are weakly affected by linear spin-orbit coupling.

Hole systems exhibit significant differences in group velocities of spin branches due to spin-orbit interactions.

Interplay of Coulomb and spin-orbit interactions is more pronounced in holes, affecting observable properties.

Abstract

We study the influence of spin-orbit interactions on quasiparticle dispersions in two-dimensional electron and heavy-hole liquids in III-V semiconductors. To obtain closed-form analytical results, we restrict ourselves to spin-orbit interactions with isotropic spectrum and work within the screened Hartree-Fock approximation, valid in the high-density limit. For electrons having a linear-in-momentum Rashba (or, equivalently, Dresselhaus) spin-orbit interaction, we show that the screened Hartree-Fock approximation recovers known results based on the random-phase approximation and we extend those results to higher order in the spin-orbit coupling. While the well-studied case of electrons leads only to a weak modification of quasiparticle properties in the presence of the linear-in-momentum spin-orbit interaction, we find two important distinctions for hole systems (with a leading nonlinear-in-momentum spin-orbit interaction). First, the group velocities associated with the two hole-spin branches acquire a significant difference in the presence of spin-orbit interactions, allowing for the creation of spin-polarized wavepackets in zero magnetic field. Second, we find that the interplay of Coulomb and spin-orbit interactions is significantly more important for holes than for electrons and can be probed through the quasiparticle group velocities. These effects should be directly observable in magnetotransport, Raman scattering, and femtosecond-resolved Faraday rotation measurements. Our results are in agreement with a general argument on the velocities, which we formulate for an arbitrary choice of the spin-orbit coupling.