Quantum plasmonic non-reciprocity in parity-violating magnets

TL;DR

This paper introduces quantum metric plasmons (QMPs) in parity-violating magnetic metals, revealing their intrinsic non-reciprocal behavior driven by quantum geometry, even in symmetric dispersions, with potential realizations in materials like twisted bilayer graphene.

Contribution

The study uncovers a new class of plasmons, QMPs, whose non-reciprocity stems from quantum metric dipoles, advancing understanding of optical responses in parity-violating magnetic materials.

Findings

QMPs exhibit intrinsic non-reciprocity due to quantum metric dipoles.

QMP non-reciprocity persists even with symmetric single-particle dispersions.

Potential realization of QMPs in twisted bilayer graphene and similar materials.

Abstract

The optical responses of metals are often dominated by plasmonic resonances - the collective oscillations of interacting electron liquids. Here we unveil a new class of plasmons - quantum metric plasmons (QMPs) - that arise in a wide range of parity violating magnetic metals. In these materials, a dipolar distribution of the quantum metric (a fundamental characteristic of Bloch wavefunctions) produces intrinsic non-reciprocal bulk plasmons. Strikingly, QMP non-reciprocity manifests even when the single-particle dispersion is symmetric: QMPs are sensitive to time-reversal and parity violations hidden in the Bloch wavefunction. In materials with asymmetric single-particle dispersions, quantum metric dipole induced non-reciprocity can continue to dominate at large frequencies. We anticipate that QMPs can be realized in a wide range of parity violating magnets, including twisted bilayer graphene heterostructures, where quantum geometric quantities can achieve large values.