Experimental Development of a Radiative Thermal Memristor.

We report the experimental realization of a radiative thermal memristor made of a 200-nm-thick VO2 film exchanging heat by far-field radiation with a heat-flux sensor. This two-terminal device exploits the metal-insulator transition and thermal hysteresis of VO2, exhibiting large emissivity variations and a hysteresis width of 5 K around the mean temperature T0 = 338.7 K. Under low-frequency sinusoidal modulation of the VO2 temperature around T0, we observe a pinched, infinity-shaped Lissajous curve for the heat flux versus temperature difference. From this characteristic curve we extract a history-dependent thermal memristance with clear ON and OFF states defined by the emissivity contrast between its insulating and metallic phases. These memristive states remain robust over multiple cycles, enabling binary information encoding in a purely radiative configuration. Our results demonstrate the operation of a contactless thermal memristor and provide a fundamental element for thermal memories, thermal neurons, and neuromorphic networks analogous to their electrical counterparts.