Low-temperature thermal transport in moir\'e superlattices

TL;DR

This paper investigates how moiré superlattices affect phonon thermal conductivity at low temperatures, revealing significant reductions and enhancements due to phonon band reconstruction and group velocity changes.

Contribution

It provides a continuum and semiclassical analysis of phonon thermal transport in moiré bilayers, highlighting the impact of twist angle on thermal conductivity behavior.

Findings

Thermal conductivity decreases near zero twist angle at low temperatures.

Moiré effects can enhance thermal conductivity beyond non-moiré systems at zero temperature.

Temperature dependence deviates from quadratic behavior in moiré superlattices.

Abstract

We calculate the phonon thermal conductivity of various moir\'e bilayer systems using a continuum approach and the semiclassical transport theory. When the twist angle is close to 0, we observe a significant reduction of thermal conductivity in a particular low-temperature regime. This reduction is attributed to a moir\'e-induced reconstruction of acoustic phonon bands and associated decrease of the group velocity. Conversely, in the zero temperature limit, the thermal conductivity is enhanced by moir\'e effect, surpassing the original values in non-moir\'e counterparts. These changes result in a characteristic temperature dependence which deviates from the quadratic behavior in intrinsic two-dimensional systems.