Physicists find a way to control heat in a way once thought impossible

Physicists have developed a material capable of controlling heat in a manner once deemed impossible, potentially revolutionizing energy systems and information storage. This groundbreaking material, detailed in a June 25 study published in Laser & Photonics Reviews, circumvents a century-old principle of physics that dictates how materials absorb and emit heat.

Traditionally, materials that absorb heat in one direction also emit heat in that same direction, a rule known as reciprocity. This limitation has constrained engineers' ability to independently manage incoming and outgoing heat.

The researchers ingeniously crafted a theoretical device utilizing two incompatible materials. By applying a magnetic field, they disrupted the inherent symmetry of an indium arsenide layer, a substance that naturally absorbs and emits infrared light. This disruption led to divergent radiation behavior depending on the direction of travel.

Overlying this layer is a grating composed of a phase-changing material, germanium-antimony-tellurium (GST), which can adopt and maintain two distinct physical structures. Once set into position, the GST layer locks the directional difference of radiation in place, retaining this programmed behavior even when the power is switched off—a feat known as nonvolatility.

Professor Juejun Hu, a materials science expert at MIT not involved in the study, praised the innovative approach, highlighting the seamless integration of magneto-optical nonreciprocity with a nonvolatile phase-change material. This combination is particularly noteworthy because it functions effectively even at minute angles—just 3 degrees off a straight line, making it far more practical for practical applications.

Unlike prior attempts that only succeeded at wider angles, this device can be seamlessly incorporated into existing optical systems.

While the device remains a theoretical construct, its reliance on established materials and manufacturing techniques makes it a plausible reality. However, one hurdle remains: the GST layer's thickness could complicate frequent switching between structures. Nonetheless, the potential applications are vast, with the most immediate use likely being in infrared sensing, where direction-selective heat absorption is highly beneficial.