# Modulation of Radiative Heat Transfer at the Nanoscale via Topological Polaritons in Twisted van der Waals Crystals

## TL;DR

Researchers show that adjusting the twist angle in α-MoO3 layers can control heat transfer at the nanoscale through topological changes in polaritons.

## Contribution

This work introduces twistoptics as a novel method to modulate near-field radiative heat transfer using topological transitions in twisted van der Waals crystals.

## Key findings

- Increasing the twist angle in α-MoO3 bilayers monotonically increases heat flux.
- Topological transitions from hyperbolic to elliptical polaritonic dispersions explain the modulation of heat transfer.
- Gapped trilayers of α-MoO3 offer greater flexibility in regulating near-field radiative heat transfer.

## Abstract

Twisted layers of α‐MoO3 support phonon polaritons whose propagation can be adjusted by the twist angle, a concept known as ‘twistoptics’. Although emergent in the field of nano‐optics, the application to heat transfer has lagged behind, particularly regarding near‐field radiative heat transfer (NFRHT), which is important for thermal management in nanodevices and remains insufficiently explored. Here, we report the role of twistoptics in NFRHT, demonstrating that the heat flux between two separated twisted α‐MoO3 bilayers can be monotonically increased by simply increasing the twist angle. Interestingly, this modulation is explained by the emergence of topological transitions from open (hyperbolic) to closed (elliptical) polaritonic dispersions. This phenomenon is further demonstrated by considering α‐MoO3 gapped trilayers, which show greater flexibility in regulating the NFRHT due to the emergence of a wider variety of topological transitions. Based on these findings, we propose an experimental scenario where the NFRHT between a nanoparticle and a closely spaced twisted α‐MoO3 bilayer can be modulated by a factor of 3 by simply adjusting the twist angle. This work provides theoretical guidance for the modulation of NFRHT using twistoptics, making an important step toward the development of twisted thermotics.

Twisted α‐MoO3 layers support phonon polaritons whose propagation depends on the twist angle, enabling control of near field radiative heat transfer. Increasing the angle yields a monotonic rise in heat flux, driven by topological transitions from open hyperbolic to closed elliptical dispersions.