4 research outputs found
Absent thermal equilibration on fractional quantum Hall edges over macroscopic scale
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. Such 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
Heat Conductance of the Quantum Hall Bulk
The Quantum Hall Effect (QHE) is the prototypical realization of a
topological state of matter. It emerges from a subtle interplay between
topology, interactions, and disorder. The disorder enables the formation of
localized states in the bulk that stabilize the quantum Hall states with
respect to the magnetic field and carrier density. Still, the details of the
localized states and their contribution to transport remain beyond the reach of
most experimental techniques. Here, we describe an extensive study of the
bulk's heat conductance. Using a novel 'multi-terminal' device, we separate the
longitudinal thermal conductance (due to bulk's contribution)
from the two-terminal value , by eliminating the contribution of
the edge modes. We find that when the field is tuned away from the conductance
plateau center, the electronic states of the bulk conduct heat efficiently
while the bulk remains electrically insulating. For fragile fractional states,
such as the non-Abelian , we observe a finite
throughout the plateau. We identify the localized states as the cause of the
finite and propose a theoretical model which qualitatively
explains our findings.Comment: 26 pages 9 figure
Absent thermal equilibration on fractional quantum Hall edges over macroscopic scale
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. Such 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