Intrinsic nonreciprocal bulk plasmons in noncentrosymmetric magnetic systems

TL;DR

This paper reveals that bulk plasmons in noncentrosymmetric magnetic systems exhibit intrinsic nonreciprocity due to underlying symmetries, with implications for nanoscale photonics and nonreciprocal light propagation.

Contribution

It uncovers the geometric origins of nonreciprocal bulk plasmons, linking quantum metric quantities to asymmetric dispersion in specific material models.

Findings

Interband and intraband plasmons show asymmetric dispersion depending on wavevector sign.

Quantum metric connection and dipole govern nonreciprocity in plasmon modes.

Numerical evidence in Qi-Wu-Zhang model and moire systems like twisted bilayer graphene.

Abstract

Nonreciprocal plasmonics enables one-way light propagation at the nanoscale and it is an essential building block for photonics applications. Here, we explore intrinsic nonreciprocity in bulk plasmon propagation based on underlying symmetries. We demonstrate that the interband, as well as the intraband bulk plasmon modes, follow asymmetric dispersion depending on the sign of the wavevector for systems with broken inversion and time-reversal symmetry. We show that the nonreciprocity in the interband plasmon dispersion is dictated by the quantum metric connection, which is a band geometric quantity. The intrinsic nonreciprocity in bulk intraband plasmon dispersion is dictated by the quantum metric dipole and a higher-order `Drude' weight-like term. We corroborate our findings via explicit numerical calculations for the two-dimensional Qi-Wu-Zhang model and demonstrate the existence of intrinsic nonreciprocal intraband and interband plasmon modes in moire systems such as twisted bilayer graphene.