Dr. zeno Bacciconi

Theory of fractional quantum Hall liquids coupled to quantum light and emergent graviton-polaritons

Recent breakthrough experiments [1, 2] have demonstrated how it is now possible to explore the dynamics of quantum Hall states interacting with quantum electromagnetic cavity fields. While the impact of strongly coupled non-local cavity modes on integer quantum Hall physics has been recently addressed, the effects on fractional quantum Hall (FQH) liquids – and, more generally, fractionalized states of matter – remain largely unexplored. In this talk I will discuss our recent efforts [3] in understanding the fate of FQH states under the action of quantum light. Combining analytical arguments with tensor network simulations, we study the dynamics of a ν = 1/3 Laughlin state in a single-mode cavity with finite electric field gradients. The existence of cavity field gradients is crucial to achieve a finite coupling with intra-Landau Level excitations as these have a vanishing dipole moment. We inspect the resilience of topological order by calculating the bulk Hall resistivity and by studying bipartite entanglement spectra. The latter carry direct fingerprints of light-matter entanglement and topology, revealing peculiar polaritonic replicas of the U(1) counting. As a further response to cavity fluctuations, we also find a squeezed anisotropic FQH geometry, encoded in long-wavelength correlations. Only at very strong cavity field gradients finite systems become unstable towards the formation a sliding Tomonaga-Luttinger liquid phase, featuring a strong density modulation in the gradient direction. Finally, by exploring the low-energy excited spectrum inside the FQH phase, we identify a new quasiparticle, the graviton-polariton, arising from the hybridization between quadrupolar FQH collective excitations (known as gravitons [4]) and light. I will then discuss the experimental implications of our findings and possible extension of our results to more complex scenarios. [1] F. Appugliese, J. Faist et. al. , Science 375, 1030 (2022). [2] J. Enkner, J. Faist et. al. , arXiv:2311.10462 (2023). [3] Z. Bacciconi, H. Xavier, I. Carusotto, T. Chanda, and M. Dalmonte , arXiv:2405.12292 (2024). [4] J. Liang, Z. Liu, Z. Yang, Y. Huang, U. Wurstbauer, C. R. Dean, K. W. West, L. N. Pfeiffer, L. Du, and A. Pinczuk, Nature 628, 78 (2024).