Absent thermal equilibration on fractional quantum Hall edges over macroscopic scale

TL;DR

This study reveals that in fractional quantum Hall states, heat transport along edges with counter-propagating modes remains nearly ballistic over large distances, despite rapid charge equilibration, highlighting unique thermal properties.

Contribution

It demonstrates the inefficiency of heat equilibration and the emergent quantization of heat conductance in fractional quantum Hall edges with counter-propagating modes.

Findings

Charge modes equilibrate rapidly.

Heat transport remains nearly ballistic over macroscopic scales.

Quantized heat conductance observed at a strong interaction fixed point.

Abstract

Two-dimensional topological insulators, and in particular quantum Hall states, are characterized by an insulating bulk and a conducting edge. Fractional states may host both downstream (dictated by the magnetic field) and upstream propagating edge modes, which leads to complex transport behavior. Here, we combine two measurement techniques, local noise thermometry and thermal conductance, to study thermal properties of states with counter-propagating edge modes. We find that, while charge equilibration between counter-propagating edge modes is very fast, the equilibration of heat is extremely inefficient, leading to an almost ballistic heat transport over macroscopic distances. Moreover, we observe an emergent quantization of the heat conductance associated with a strong interaction fixed point of the edge modes. This new understanding of the thermal equilibration on edges with counter-propagating modes is a natural route towards extracting the topological order of the exotic 5/2 state.