Phase Space Crystal Vibrations: Chiral Edge States with Preserved Time-reversal Symmetry

TL;DR

This paper demonstrates that interactions in phase-space crystals can produce topologically nontrivial phonon states with chiral edge transport, even while preserving time-reversal symmetry, challenging conventional understanding.

Contribution

It introduces a novel mechanism for topological phonon states in phase-space crystals arising from atom-atom interactions with complex phases, without breaking time-reversal symmetry.

Findings

Phonon Chern insulator can be realized in phase-space crystals.

Chiral edge states exist despite preserved time-reversal symmetry.

Implications for 2D charged particle dynamics in magnetic fields.

Abstract

It was recently discovered that atoms subject to a time-periodic drive can give rise to a crystal structure in phase space. In this work, we point out the atom-atom interactions give rise to collective phonon excitations of phase-space crystal via a pairing interaction with intrinsically complex phases that can lead to a phonon Chern insulator, accompanied by topologically robust chiral transport along the edge of the phase-space crystal. This topological phase is realized even in scenarios where the time-reversal transformation is a symmetry, which is surprising because the breaking of time-reversal symmetry is a strict precondition for topological chiral transport in the standard setting of real-space crystals. Our work has also important implications for the dynamics of 2D charged particles in a strong magnetic field.