arXiv subjects

Linxiao Zhu

Publications and source records attributed to Linxiao Zhu.

5 recordsLinked to original sources

arXiv2026

Designing Strong and Broadband Nonreciprocal Thermal Radiation in Magnetic Topological Materials

Breaking reciprocity in thermal radiation opens opportunities for energy harvesting, sensing, and thermal management. Traditional nonreciprocal radiative semiconductor devices need external magnetic field. In this work, we predict a series of magnetic topological materials for magnetic-field-free nonreciprocal thermal radiation in the infrared regime, by combining first-principles calculations with Maxwell electrodynamics. We find strong and broadband nonreciprocity in magnetic Weyl semimetals (e.g., Co$_3$Sn$_2$S$_2$), outperforming the conventional semiconductor such as InAs. Furthermore, we propose universal material design recipes: strong nonreciprocity requires a large anomalous Hall response relative to the optical loss, whereas the broadband response favors large optical loss and small dielectric dispersion. Our work establishes a predictive materials-discovery framework and quantitative design rules for next-generation magnet-free nonreciprocal thermal devices.

cond-mat.mtrl-sci↗

arXiv2025

Near-field photon Nernst effect

We consider the consequence of having nonreciprocal photon transfer between two surfaces with temperature gradient. We demonstrate that in a system consisting of graphene and a magneto-optical substrate separated by a gap, a transverse electric field is generated in graphene perpendicular to magnetic field and temperature gradient, in analogy to the Nernst effect. Such photon Nernst effect is driven by nonreciprocal Casimir force carried by photons. We show that the thermal efficiency of near-field photon Nernst effect is bounded by the Carnot limit, and nonreciprocal high-k modes are needed for approaching the limit. The near-field photon Nernst effect enables electrical probing of nonreciprocal radiative transfer and provides a novel means of energy harvesting.

physics.optics↗

arXiv2025

Observation of Strong Nonreciprocal Thermal Emission

The Kirchhoff`s law of thermal radiation stating the equivalence of emissivity and absorptivity at the same wavelength, angle, and polarization, has completely constrained emission and absorption processes. Achieving strong nonreciprocal emission points to fundamental advances for applications such as energy harvesting, heat transfer, and sensing, but strong nonreciprocal thermal emission has not been experimentally realized. Here, we observe strong nonreciprocal thermal emission using a custom-designed angle-resolved magnetic thermal emission spectroscopy and an epitaxially-transferred gradient-doped metamaterial. We show that under magnetic field, the metamaterial strongly breaks the Kirchhoff`s law, with a difference between emissivity and absorptivity at the same wavelength and angle reaching as high as 0.43. Significant nonreciprocal emission persists over broad spectral and angular ranges. The demonstration of strong nonreciprocal thermal emission and the approach can be useful for systematic exploration of nonreciprocal thermal photonics for thermal management, infrared camouflage, and energy conversion.

physics.optics↗

arXiv2016

Persistent Directional Current at Equilibrium in Nonreciprocal Many-Body Near Field Electromagnetic Heat Transfer

We consider the consequence of nonreciprocity in near-field heat transfer by studying systems consisting of magneto-optical nanoparticles.We demonstrate that, in thermal equilibrium, a nonreciprocal many-body system in heat transfer can support a persistent directional heat current, without violating the second law of thermodynamics. Such a persistent directional heat current cannot occur in reciprocal systems, and can only arise in many-body systems in heat transfer. The use of nonreciprocity therefore points to a new regime of near-field heat transfer for the control of heat flow in the nanoscale.

physics.optics↗

arXiv2015

Near-field radiative heat transfer between nanostructures in the deep sub-wavelength regime

Radiative heat transfer between parallel objects separated by deep sub-wavelength distances and subject to large thermal gradients (>100 K) could enable breakthrough technologies for electricity generation and thermal transport control. However, thermal transport in this regime has never been achieved experimentally due to the difficulty of maintaining large thermal gradients over nm-scale distances while avoiding other heat transfer mechanism such as conduction. Previous experimental measurement between parallel planes were limited to distances greater than 500 nm (with a 20 K thermal gradient), which is much larger than the theoretically predicted distance (<100 nm) required for most applications. Here we show near-field radiative heat transfer between parallel nanostructures in the deep sub-wavelength regime using high precision micro electromechanical (MEMS) displacement control. We also exploit the high mechanical stability of structures under high tensile stress to minimize thermal buckling effects and maintain small separations at large thermal gradients. We achieve an enhancement of heat transfer of almost two orders of magnitude relative to the far-field limit, which corresponds to a 54 nm separation. We also achieve a high temperature gradient (260 K) between the cold and hot surfaces while maintaining a ~100 nm distance.

cond-mat.mes-hall↗