Correlated insulator Moiré bolometer

Abstract

Light incident on an insulator is generally not expected to turn it into a metal without invoking intense ultrafast excitation that leads to transient structural transitions. Here we show that magic-angle twisted bilayer graphene tuned to half filling of the moiré band provides a notable exception to this expectation. We find that weak long-wavelength photons, with energies comparable to the flat-band width, selectively heat the low-heat-capacity electronic subsystem, thereby suppressing the correlated gap. This produces a giant resistance change governed not by a persistent photocarrier population, but by the extreme sensitivity of a many-body correlated gap to weak electronic heating. The resulting photon-driven insulator-to-metal transition produces a broadband low-noise photoresponse with voltage responsivity exceeding millivolts per nW of absorbed power. The mechanism is dual to superconducting hot-electron response: radiation-heated electrons suppress a many-body order, but in reverse the correlated insulator melts into a metal, providing robustness to magnetic fields of several tesla and a sharp insulator-to-metal resistive contrast. Our results establish correlated flat-band systems as a platform for ultrasensitive detection of faint long-wavelength radiation. Light irradiation can change the resistance of a material, but it is not expected to convert it into a metal without inducing structural transitions. Here, the authors report evidence of the photon-driven collapse of a many-body correlated energy gap in magic-angle twisted bilayer graphene, leading to a high voltage responsivity per absorbed power in the THz range.