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

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.