Polaritonic Insights into Emergent Quantum Phases

by Prof. Shuai Zhang(张帅) (Fudan University)

Friday 30 Jan 2026, 10:30 → 11:30 Asia/Shanghai

Tsung-Dao Lee Institute/N4F-N400 - meeting room (Tsung-Dao Lee Institute)

Host: Prof. Jinbo Peng  

Venue: TDLI Meeting Room N400

Tencent Meeting link: https://meeting.tencent.com/dm/A8xSNWUtxCcg 

Meeting ID: 915970058, no password

 

Abstract:

Polaritons—hybrid quasiparticles formed by strong light–matter coupling—exhibit extreme electromagnetic confinement. When combined with the high tunability and versatile stacking of two-dimensional quantum materials, they provide unprecedented opportunities to engineer and explore exotic quantum phases.

In this talk, I will present our recent advances in infrared nano-optics of quantum materials, enabled by a custom-developed cryogenic scattering-type scanning near-field optical microscope (s-SNOM). I will first introduce the design and capabilities of our in-house–built s-SNOM system. I will then demonstrate how nano-infrared plasmon imaging can be used to probe moiré polarization. We find that the plasmonic response is highly sensitive to the underlying moiré potential landscape, enabling spatially resolve imaging of polarization domains and, importantly, allowing us to challenge the widely accepted notion of moiré ferroelectricity [1]. Finally, I will show that hyperbolic phonon polaritons can be harnessed to enhance vacuum fluctuations, through which we successfully engineer the superfluid density of adjacent superconducting layers [2]. If time permits, I will also present our recent observation of plasmon-polaritonic bistability, an emerging nonlinear state realized through resonant tunneling and the highly tunable plasmonic response of van der Waals materials [3]. Together, these results establish polaritons as a powerful platform for sensing, controlling, and designing quantum phases in van der Waals heterostructures.

 

References:

[1] S. Zhang et al., Phys. Rev. X 15, 011019 (2025).

[2] I. Keren†, T. A. Webb†, S. Zhang† et al., arXiv:2505.17378 (2025). (Nature, in press).

[3] S. Zhang et al., arXiv:2512.02909, Phys. Rev. Lett. DOI: 10.1103/7xlm-s3s5 (2025).

 

Biography:

Shuai Zhang is an assistant professor in the Department of Physics at Fudan University. He received his Ph.D. from Fudan University and subsequently worked as a postdoctoral researcher and associate research scientist at Columbia University. His research focuses on infrared and terahertz nano-optics of quantum materials, particularly polaritons, moiré systems, and strongly correlated phases. He has developed advanced cryogenic near-field optical microscopy techniques to probe and control quantum phenomena at the nanoscale. His work has been published in journals including Physical Review Letters, Physical Review X, and Nature.