Temperature-independent thermal radiation

TL;DR

This paper presents ultrathin thermal emitters using samarium nickel oxide that achieve temperature-independent thermal radiation by exploiting a reversible phase transition, challenging traditional laws of thermal emission.

Contribution

The study demonstrates a novel approach to control thermal emissivity through a phase transition in a quantum material, enabling temperature-independent thermal emission.

Findings

Achieved temperature-independent emission in the 8-14 μm range.

Utilized a reversible insulator-metal phase transition in SmNiO3.

Enabled new control over heat transfer and infrared visibility.

Abstract

Thermal emission is the process by which all objects at non-zero temperatures emit light, and is well-described by the classic Planck, Kirchhoff, and Stefan-Boltzmann laws. For most solids, the thermally emitted power increases monotonically with temperature in a one-to-one relationship that enables applications such as infrared imaging and non-contact thermometry. Here, we demonstrate ultrathin thermal emitters that violate this one-to-one relationship via the use of samarium nickel oxide (SmNiO3), a strongly correlated quantum material that undergoes a fully reversible, temperature-driven solid-state phase transition. The smooth and hysteresis-free nature of this unique insulator-to-metal (IMT) phase transition allows us to engineer the temperature dependence of emissivity to precisely cancel out the intrinsic blackbody profile described by the Stefan-Boltzmann law, for both heating and cooling. Our design results in temperature-independent thermally emitted power within the long-wave atmospheric transparency window (wavelengths of 8 - 14 um), across a broad temperature range of ~30 {\deg}C, centered around ~120 {\deg}C. The ability to decouple temperature and thermal emission opens a new gateway for controlling the visibility of objects to infrared cameras and, more broadly, new opportunities for quantum materials in controlling heat transfer.