Excitations in a spin-polarized tow-dimensional electron gas

TL;DR

This paper investigates the properties of spin plasmons in a two-dimensional spin-polarized electron gas, revealing how spin-dependent correlations influence their dispersion, damping, and excitation spectrum, including a novel magnetic antiresonance feature.

Contribution

It introduces a method to incorporate spin-dependent correlations into response functions, showing significant modifications to spin plasmon behavior beyond the random phase approximation.

Findings

Spin plasmon dispersion is significantly lowered.

Critical wave vector for Landau damping is reduced.

Discovery of a magnetic antiresonance with potential experimental observation.

Abstract

A remarkably long-lived spin plasmon may exist in two-dimensional electron liquids with imbalanced spin up and spin down population. Predictions for this interesting mode by Agarwal et al. [Phys. Rev. B 90, 155409 (2014)] are based on the random phase approximation. We here show how to account for spin dependent correlations from known ground state pair correlation functions and study the consequences on the various spin dependent longitudinal response functions. The spin plasmon dispersion relation and its critical wave vector for Landau damping by minority spins turn out to be significantly lowered. We further demonstrate that spin dependent effective interactions imply a rich structure in the excitation spectrum of the partially spin-polarized system. Most notably, we find a "magnetic antiresonance", where the imaginary part of both, the spin-spin as well as the density-spin response function vanish. The resulting minimum in the double-differential cross section is awaiting experimental confirmation.