A Discovery Born in Hamburg

The breakthrough traces its origins to Hamburg, where McIver led a research group at the Max Planck Institute for the Structure and Dynamics of Matter (MPSD). The institute is part of the Max Planck–New York Center on Nonequilibrium Quantum Phenomena, a collaboration with Columbia University, the Flatiron Institute, and Cornell University. Together, these researchers explore how stable systems behave when pushed out of equilibrium.

Figure 1. Hidden Quantum Mirrors Found Trapping Light Inside 2D Materials.

Shrinking Light to Reveal Hidden Quantum Waves

To overcome the vast size mismatch between light and 2D materials, the team built a miniature, chip-scale spectroscope capable of compressing terahertz (THz) light—from about one millimeter down to just three micrometers. This breakthrough allowed them to directly observe how electrons move and interact within ultra-thin systems. Their first test subject was graphene, chosen for its well-documented optical properties. But what they found went beyond expectations—standing waves appeared where none were supposed to exist. Figure 1 shows Hidden Quantum Mirrors Found Trapping Light Inside 2D Materials.

Hybrid Light–Matter Waves

“Light can couple with electrons to form hybrid light–matter quasiparticles,” explained MPSD postdoctoral fellow and co–first author Hope Bretscher. “These quasiparticles behave like waves and can become confined—just like a standing wave on a guitar string that produces a single note.”

In a guitar, the string’s fixed ends define the wave’s boundaries. Shortening the string shifts the vibration frequency and changes the pitch. In optics, mirrors can serve a similar purpose by trapping light between them to create standing waves inside a cavity. When a material is placed between these mirrors, the trapped light can strongly interact with it, reshaping its properties.

“We found that the material’s own edges act as mirrors,” said first author Gunda Kipp. Using their THz spectroscope, the team saw that excited electron waves reflected off the edges of the material, forming plasmon polaritons—hybrid light–matter quasiparticles that naturally confine themselves.

The researchers examined a layered device in which each layer acted as a separate cavity, separated by only a few tens of nanometers. The plasmons in these layers interacted strongly with each other—so much so that linking them altered their resonant frequencies. “It’s like connecting two guitar strings; once they’re coupled, the note changes,” Bretscher said. “In our case, it changes dramatically.”

Understanding and Designing Quantum Behavior

The next challenge was to determine what controls the frequencies of these quasiparticle vibrations and how strongly light and matter interact. “Together with co-author Marios Michael, we developed an analytical model that only needs a few geometric parameters to match the results of our experiments,” said Kipp. “With a single calculation, the theory can extract a material’s properties and help design new samples with tailored quantum characteristics.”

By tracking how these resonances shift under changing conditions—such as carrier density, temperature, or magnetic field—the team hopes to uncover the mechanisms behind exotic quantum phases.

Source:SciTECHDaily

Cite this article:

Priyadharshini S (2025), Physicists Discover Hidden Quantum Mirrors That Confine Light Within 2D Materials, AnaTechMaz, pp. 295