Physics Department - Quantized Light-Matter Interaction beyond Classical Limits: From Meta to Quantum Optoelectronics

Abstract
Light-matter interaction, spanning vast energy and length scales, is at the heart of the technologies driving our modern world. Light serves as a sustainable energy source, an efficient information carrier, and a bridge between humans and machines. Meanwhile, electrons enable energy storage, information processing, and logic operations within materials. At the nanoscale, new opportunities emerge as light and electronic states naturally couple strong and become quantized, producing discrete resonances in metallic and dielectric nanostructures and enhanced quasi-particle and collective excitations in 2D materials.

In this seminar, I will talk about a series of coherent efforts to create cutting-edge nanostructures for achieving unprecedented control over extreme and quantized photon-electron interactions, paving the way for revolutionary devices and deeper insights into unexplored physics. We start the investigation by shrinking down the size of bulk materials to hundreds of nanometers. The resulting engineered nanostructures provide a rich library of quantized optical resonant modes [1], enabling precise manipulation of light and the integration of electronic and optical components in ways that break conventional limits [2-4]. Further miniaturization of nanomaterials to atomically thin limits reduces optical confinement but enhances quantum confinement and suppresses dielectric screening. These effects unlock the quantized quasi-particle and collective excitations in low-dimensional materials, enabling strong and tunable interactions with free-space light as well [5], leading to the creation of functional optical elements as thin as atoms [6].

The exciting story continues with the synergy between the above mentioned two material platforms: by selectively interacting with targeted quantum states and driving materials to the well-designed far-from-equilibrium phase, these tailored nanostructures become powerful tools for probing and controlling exotic quantum behaviors in low-dimensional materials. Here, we exemplify this concept by studying the exciton properties and dynamics in 2D semiconductors with carefully engineered optical, electrical, and mechanical nano-environments. Ultimately, by merging advanced device technology with a profound understanding of quantum materials, my work may enable harnessing quantum light and matter in more controllable ways, driving innovations in quantum communication, simulation, and computing.

References

[1] Qitong Li, et al., “Structural color from a coupled nanowire pair beyond the bonding and anti-bonding model,” Optica 8, 464-470 (2021).
[2] Qitong Li et al., “Transparent Multispectral Photodetectors Mimicking the Human Visual System,” Nature Communications 10, e4982 (2019).
[3] Qitong Li et al., “Metasurface Optofluidics for Dynamic Control of Light Fields,” Nature Nanotechnology 17, 1097-1103 (2022).
[4] Son Tung Ha*, Qitong Li* et al., “Optoelectronic Metadevices,” Science, 386, eadm7442 (2024).
[5] Qitong Li, et al., “A Purcell Enabled Monolayer Semiconductor Free-Space Optical Modulator,” Nature Photonics 17, 897-903 (2023). 
6] Melissa Li, Qitong Li†, Mark L. Brongersma†, Harry A. Atwater†, “Optical devices as thin as atoms,” Science, 386, adk7707 (2024).