Faint far-infrared radiation drives a correlated insulator-to-metal transition in magic-angle graphene
One of the central ideas in modern physics is the phase transition—a sudden transformation of the state of a material. We encounter phase transitions throughout everyday life: water freezes into ice, wax melts in the warmth of a flame, and water vapor condenses into droplets on a cold window. In these familiar examples, the atoms themselves rearrange into a new structure, giving the material…
In a recent study published in Nature Communications, researchers from the National University of Singapore demonstrated that magic-angle twisted bilayer graphene (MATBG) can transition from a correlated insulator to a metallic state when exposed to faint far-infrared (FIR) radiation. This phenomenon occurs even at very low radiation intensities, which is remarkable since FIR radiation is difficult to detect.
The key to this transition lies in the unique electronic structure of MATBG, which is created by stacking two graphene sheets with a relative rotation of about one degree. This special angle causes the electronic bands to become extremely narrow, intensifying electron-electron interactions. Under appropriate conditions, these interactions can give rise to a correlated insulating state, where electrical conduction is strongly suppressed.
When MATBG is exposed to FIR radiation, the photons selectively heat the electrons while the crystal lattice remains cold. This tiny increase in electron temperature is sufficient to melt the fragile insulating state and restore metallic conduction. The implications of this discovery are both scientifically intriguing and practically significant.
Investigating the delicate collective behavior of electrons in such fragile phases offers new insights into quantum materials. Moreover, the ability to switch between insulating and metallic states using a simple gate voltage and a faint beam of FIR light makes MATBG a promising platform for developing sensitive far-infrared detectors.
These detectors could find applications in various fields, including medical diagnostics, security screening, and observational astronomy.
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