Strong suppression of near-field thermal transport between twisted bilayer graphene near the magic angle

TL;DR

This study theoretically demonstrates that near-field thermal transport between twisted bilayer graphene is significantly suppressed near the magic angle, with potential for thermal control applications.

Contribution

It provides a detailed theoretical analysis of thermal transport suppression in twisted bilayer graphene near the magic angle, considering various factors like temperature, gap size, and substrate effects.

Findings

Heat flow is suppressed near the magic angle due to reduced Drude weight.

Over 100-fold heat-flow variation achievable at low temperature and specific twist angles.

Suppression can exceed 10,000-fold by reducing electron scattering rate.

Abstract

Twisted bilayer graphene (TBLG) has recently emerged as a versatile platform for studying a variety of exotic transport phenomena. Here, we present a theoretical study of near-field thermal radiation between suspended TBLG with a focus on the magic angle. Within the chirally symmetric continuum model, we observe a suppressed heat flow when approaching the magic angle owing to a reduced Drude weight, with greater suppressions at lower temperatures and larger gap sizes. When the chemical potential lies in the energy gap near the charge neutrality point, more than 100-fold heat-flow variation can be achieved at 50 K within 0.25{\deg}of twist. By reducing the electron scattering rate, the radiation spectrum near the magic angle dramatically narrows, leading to over 10,000-fold of suppression. In addition, supported TBLG is briefly considered to facilitate experimental measurement. With rationally tailored substrates, the heat-flow contrast can still exceed 1000. We also discuss lattice relaxation effect in terms of the interlayer coupling energy, finding that a stronger coupling leads to a smaller heat-flow contrast and more prominent multiband transport. Our results highlight the great potential of magic-angle TBLG in thermal transport, especially for controlling thermal radiation.