Interplay of spin-orbit coupling and Zeeman splitting in the absorption lineshape of 2D fermions

TL;DR

This paper explores how spin-orbit coupling and Zeeman splitting influence the ESR absorption lineshape in 2D fermions, revealing divergence at spectrum edges and temperature-dependent features near the compensation point.

Contribution

It models ESR response considering strong spin-orbit coupling, extending previous work by not assuming small elta_{SO} compared to elta_Z, and links ESR features to spin-liquid states.

Findings

ESR response diverges at absorption spectrum edges for perpendicular ac magnetic field.

Features in the absorption spectrum evolve with temperature near the compensation point.

The model applies to 2D electron gases with Rashba spin-orbit coupling, relevant for spin-liquid probes.

Abstract

We suggest that electron spin resonance (ESR) experiment can be used as a probe of spinon excitations of hypothetical spin-liquid state of frustrated antiferromagnet in the presence of asymmetric Dzyaloshinskii-Moriya (DM) interaction. We describe assumptions under which the ESR response is reduced to the response of 2D electron gas with Rashba spin-orbit coupling. Unlike previous treatments, the spin-orbit coupling, \Delta_{SO}, is not assumed small compared to the Zeeman splitting, \Delta_Z. We demonstrate that ESR response diverges at the edges of the absorption spectrum for ac magnetic field perpendicular to the static field. At the compensation point, \Delta_{SO}\approx \Delta_Z, the broad absorption spectrum exhibits features that evolve with temperature, T, even when T is comparable to the Fermi energy.