Electromagnetic Response of a Half-Filled Chern Band near Topological Criticality

TL;DR

This paper investigates electromagnetic responses in a half-filled Chern band near a topological phase transition, revealing plasmon damping due to emergent gauge fields and analyzing related transport phenomena.

Contribution

It provides new insights into the damping of plasma modes and electromagnetic responses across a topological phase transition in a Chern band, highlighting phenomena near criticality.

Findings

Sharp plasma mode exists deep in CFL phase

Plasmon damping occurs near the phase transition

Damping persists over a finite range across the boundary

Abstract

We evaluate electromagnetic-response observables in a half-filled Chern band, across a topological phase transition between a composite Fermi liquid (CFL) and a Fermi liquid (FL) phase. While a sharp gapped plasma mode exists deep in the CFL phase, we demonstrate that it is damped near the proposed continuous phase transition between CFL and FL. This plasmon-damping phenomenon originates from emergent gauge fields and a Dirac-fermion-like spectrum. Similar features also occur in other continuous deconfined topological phase transitions, such as the Laughlin to superfluid transition in a bosonic system. In particular, this damping behavior extends over a finite range across the phase boundary, and, hence, we expect it to persist even when the transition is weakly first-order. Furthermore, we analyze the behavior of the Drude weight, the wavevector-dependent conductivity, and the chiral mirror effect across these topological phase transitions.