Spin waves in magnetic quantum wells with Coulomb interaction and $sd$ exchange coupling

TL;DR

This paper theoretically investigates the spin excitation spectrum in a 2D electron gas within a quantum well containing magnetic impurities, highlighting the interplay between Coulomb interactions and $sd$ exchange coupling and revealing significant qualitative changes.

Contribution

It introduces a new theoretical framework that considers both Coulomb interactions and $sd$ exchange coupling simultaneously, revealing complex spin wave behaviors.

Findings

Mixed spin waves propagate below the single particle continuum.

An anticrossing gap appears at a specific wavevector.

Electron kinetic damping significantly affects electron-impurity spin coupling.

Abstract

We theoretically describe the spin excitation spectrum of a two dimensional electron gas embedded in a quantum well with localized magnetic impurities. Compared to the previous work, we introduce equations that allow to consider the interplay between the Coulomb interaction of delocalized electrons and the $sd$ exchange coupling between electrons and magnetic impurities. Strong qualitative changes are found : mixed waves propagate below the single particle continuum, an anticrossing gap is open at a specific wavevector and the kinetic damping due to the electron motion strongly influences the coupling strength between electrons and impurities spins.