This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: 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 entirely different properties. But some of the most fascinating phase transitions are invisible to the naked eye. Instead of atomic rearrangement, it is the electrons that collectively reorganize into a new quantum state.
A subtle change in external parameters—temperature, magnetic field or even exposure to light—can completely transform how such a material behaves. Superconductivity is perhaps the most celebrated example of an electronic phase transition. For over a century, the superconducting state—carrying electrical current without any resistance—has captivated physicists.
Yet the transition itself is just as remarkable as the state it leads to. Near the transition point, even a tiny external stimulus produces a dramatic change in the material's properties. This extraordinary sensitivity has made superconductors the foundation of some of the world's most sensitive detectors, capable of registering individual photons arriving from distant galaxies.
In our laboratory (CMX lab) at the National University of Singapore, we investigate how emerging quantum materials interact with far-infrared (FIR) radiation—an important band of the electromagnetic spectrum that is notoriously difficult to detect. In a recent study published in Nature Communications, we showed, using magic-angle twisted bilayer graphene (MATBG) as an example, that superconductors are not the only materials whose phase transitions can be harnessed for ultrasensitive radiation detection. MATBG is formed by stacking two graphene sheets with a relative rotation of about one degree.
At this special angle, the electronic bands become extremely narrow, greatly enhancing interactions between electrons. Under the right conditions, these interactions can produce a correlated insulator—a fragile collective state in which electrical conduction is strongly suppressed. By exposing the MATBG sample to far-infrared (FIR) radiation, we found that even very low radiation intensities are sufficient to drive this correlated insulator into a metallic state.
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