Speaker
Description
Quantum vacuum fluctuations are usually negligible in solid-state systems due to their minimal strength. They have traditionally been linked to phenomena such as spontaneous emission and the Casimir effect. Recent advances in cavity engineering, however, allow for extreme compression of the photonic mode volume, enhancing considerably the vacuum electric field strength and driving light–matter interactions into the ultra-strong coupling regime.
Quantum Hall systems have provided a fertile platform for discovering new physics for more than four decades, and their coupling to the vacuum has recently attracted both experimental and theoretical attention.
In this talk, I will review recent experimental progress in the field and present our theoretical contributions. We show how electronic correlations are affected by the emergence of a cavity-mediated effective interaction that is attractive and long-ranged. This interaction modifies spin splittings driven by exchange interactions and, perhaps more remarkably, stabilizes certain fractional quantum Hall (FQH) phases. Using exact diagonalization, semi-analytical approaches, and Monte Carlo simulations, we show that these interactions indeed increase the excitation gap, a key measure of the FQH state’s robustness.
References:
J. Enkner, L. Graziotto, D. Boriçi, F. Appugliese, C. Reichl, G. Scalari, N. Regnault, W. Wegscheider, C. Ciuti, and J. Faist, “Tunable vacuum-field control of fractional and integer quantum hall phases,” Nature 641, 884–889 (2025)
D. Boriçi, N. Regnault, and C. Ciuti, “Cavity-modified fractional quantum hall phases,” in preparation (2025)
D. Boriçi, G. Arwas, and C. Ciuti, “Cavity-modified quantum electron transport in multiterminal devices and interferometers,” Phys. Rev. B 112, 045301 (2025)
C. Ciuti, “Cavity-mediated electron hopping in disordered quantum Hall systems,” Physical Review B 104 (2021).
F.Appugliese, J.Enkner, G.L.Paravicini-Bagliani, M.Beck, C.Reichl, W.Wegscheider, G.Scalari, C.Ciuti, and J.Faist, “Breakdown of topological protection by cavity vacuum fields in the integer quantum Hall effect,” Science 375, 1030–1034 (2022)
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