Spectroscopic footprints of quantum friction in nonreciprocal and chiral media

TL;DR

This paper explores how quantum friction on a moving atom near various media, including topological insulators and chiral materials, is affected by nonreciprocity and chirality, revealing new asymptotic behaviors and links between these properties.

Contribution

It generalizes quantum friction effects to media with broken time-reversal symmetry, highlighting the roles of chirality and nonreciprocity in Casimir-Polder interactions.

Findings

Different asymptotic power laws for various materials.

Identification of links between chirality and nonreciprocity via magnetoelectric coupling.

Dependence of frequency shift on optical rotatory strength and geometric magnetic fields.

Abstract

We investigate how the quantum friction experienced by a polarizable atom moving with constant velocity parallel to a planar interface is modified when the latter consists of chiral or nonreciprocal media, with special focus on topological insulators. We use macroscopic quantum electrodynamics to obtain the velocity-dependent Casimir-Polder frequency shift and decay rate. These results are a generalization to matter with time-reversal symmetry breaking. We illustrate our findings by examining the nonretarded and retarded limits for five examples: a perfectly conducting mirror, a perfectly reflecting nonreciprocal mirror, a three-dimensional topological insulator, a perfectly reflecting chiral mirror and an isotropic chiral medium. We find different asymptotic power laws for all these materials. Interestingly, we find two bridges between chirality and nonreciprocity through the frequency shift that arise as a consequence of the magnetoelectric coupling. Namely, the position-dependent Casimir-Polder frequency shift for the nonreciprocal case depend on a geometric magnetic field associated with photoionization of chiral molecules, the Casimir-Polder depending on the velocities for the chiral case have the optical rotatory strength as the atomic response while those for the nonreciprocal case depend on an analog of the optical rotatory strength.