The latest research in the journal Nature Physics shows that the layered structure of two-dimensional materials can naturally form optical cavities, providing a new perspective for understanding the generation mechanisms of quantum phases such as superconductivity. A joint team from Columbia University and the Max Planck Institute used a novel terahertz spectroscopy technique to observe the coupling phenomenon between light and electrons in two-dimensional materials.

James McIver, assistant professor of physics at Columbia University, stated: "We have discovered hidden control layers in quantum materials and opened a path to shaping the interaction between light and matter, which can both help us understand exotic phases of matter and ultimately utilize them to develop future quantum technologies." The research team employed a chip-level terahertz spectrometer to compress light wavelengths from 1 millimeter to 3 microns, successfully overcoming the technical barrier where the scale of two-dimensional materials is much smaller than the detection wavelength.

The experiment observed for the first time plasmon standing waves formed by reflections from material edges in a graphene system. Gonda Kip, a doctoral student at the Max Planck Institute, explained: "Light can couple with electrons to form hybrid light-matter quasiparticles. These quasiparticles move in the form of waves, and under certain conditions, they can be confined, just like standing waves on a guitar string producing a unique note." The study confirmed that each interlayer in the multilayer structure of two-dimensional materials can form a natural cavity, and plasmons between adjacent cavities produce strong interactions.

This discovery reveals an unrecognized control dimension in two-dimensional material systems. Postdoctoral researcher Hope Brecher pointed out: "The whole project was a bit like a serendipitous discovery. We didn’t expect to see these cavity effects, but we are very excited to be able to use these effects to regulate various phenomena in quantum materials." The analytical theoretical model established by the research team can predict material properties with only a few geometric parameters, providing a new method for designing quantum materials with specific properties.

The novel terahertz spectroscopy technique provides a universal platform for studying various quasiparticle oscillations in two-dimensional materials. The research team is currently conducting new sample measurements simultaneously in Hamburg and New York to further explore the control mechanisms of natural cavities on different quantum material systems.