Researchers at Osaka Metropolitan University, led by Professor Koichi Okamoto and Dr. Shunsuke Murai, have built a device that breaks thermal reciprocity — the long-standing physics rule stating that a material absorbing heat efficiently from one direction must emit it the same way. By combining a magneto-optical material with the phase-change compound GST, the team created a device that absorbs heat from one direction while radiating it in another.
The device can also switch its thermal behavior on and off, and because GST holds its structural state without continuous power, it "remembers" its last configuration the way flash memory retains data without a battery. Earlier prototypes lost their settings the instant power was cut and only worked at extreme, impractical angles; the Osaka team's design operates near normal incidence, making it far more practical.
The breakthrough, published in Laser & Photonics Reviews, points toward compact devices that control heat radiation "much like electronic circuits" — with potential uses in smarter infrared sensors, more efficient energy systems, and photonic memory that stores data using heat and light instead of electrical charge.