Discovery of Hidden Quantum Cavities in 2D Materials

Researchers at Columbia University and the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) have made a significant advancement in understanding two-dimensional (2D) materials, which can exhibit unique quantum properties such as superconductivity and exotic magnetism. A study published in *Nature Physics* reveals that these materials can naturally form cavities that confine light and electrons, fundamentally altering their interactions and behaviors. This discovery was facilitated by a novel terahertz (THz) spectroscopy technique that miniaturizes the measurement process to a chip-scale platform, allowing for unprecedented observation of quantum phenomena.

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The research team, led by James McIver, utilized their advanced THz spectroscope to investigate the optical conductivity of graphene, a well-known 2D material. They observed unexpected standing waves, which are indicative of hybrid light-matter quasiparticles. These quasiparticles, such as plasmon polaritons, arise when light couples with electrons, forming confined waves similar to those produced on a vibrating guitar string. Notably, the researchers found that the edges of the 2D materials themselves can act as mirrors, creating these cavities without the need for external reflective surfaces.

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To address the challenge of probing materials that are thinner than a human hair, the team developed a chip-sized spectroscope that compresses THz light from 1 millimeter down to just 3 micrometers. This innovation enables direct observation of electron behavior within 2D materials, revealing hidden dynamics that were previously inaccessible. Gunda Kipp, a PhD student and co-author of the study, emphasized the importance of this technique, stating, “By shining light on them, we can literally shed light on the hidden behavior of their electrons.”

2D Devices Have Hidden Cavities That Can Modify Electronic Behavior

The findings from this study open new avenues for manipulating quantum materials. The ability to control light-matter interactions through these cavities could lead to advancements in quantum technologies. Hope Bretscher, a postdoctoral fellow and co-author, expressed excitement about the potential applications, noting, “We didn’t expect to see these cavity effects, but we’re excited to use them to manipulate phenomena in quantum materials going forward.”

2D Devices Have Hidden Cavities That Can Modify Electronic Behavior

James McIver remarked on the significance of the discovery, stating, “We’ve uncovered a hidden layer of control in quantum materials and opened a path to shaping light–matter interactions in ways that could help us both understand exotic phases of matter and ultimately harness them for future quantum technologies.” The research team is now focused on exploring how these cavity effects might influence other materials and quantum phases.

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The researchers plan to continue their investigations by measuring new samples in both Hamburg and New York, aiming to further understand the implications of their findings on a broader range of 2D materials. This ongoing work could significantly enhance the understanding of quantum behaviors and their applications in technology.

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• “We’ve uncovered a hidden layer of control in quantum materials and opened a path to shaping light–matter interactions in ways that could help us both understand exotic phases of matter and ultimately harness them for future quantum technologies,” — James McIver, Assistant Professor of Physics, Columbia University

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• “2D materials, with their fascinating macroscopic properties, often behave like black boxes. By shining light on them, we can literally shed light on the hidden behavior of their electrons, revealing details that would otherwise remain unseen,” — Gunda Kipp, PhD Student, MPSD

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• “This whole project was a bit of a serendipitous discovery. We didn't expect to see these cavity effects, but we're excited to use them to manipulate phenomena in quantum materials going forward,” — Hope Bretscher, Postdoctoral Fellow, MPSD

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