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TT: Fachverband Tiefe Temperaturen

TT 86: Correlated Electrons: Method Development

TT 86.12: Talk

Friday, March 22, 2024, 12:30–12:45, H 3007

Engineering photon-mediated long-range spin interactions in Mott insulators — •Paul Fadler¹, Jiajun Li², Kai Phillip Schmidt¹, and Martin Eckstein³ — ¹Friedrich-Alexander-Universität Erlangen-Nürnberg — ²Paul Scherrer Institut — ³Universität Hamburg

We investigate the potential to induce long-range spin interactions in a Mott insulator via the quantum electromagnetic field of a cavity. The coupling between light and spins is inherently non-linear and occurs via multi-photon processes like Raman scattering and two-photon absorption/emission with electronically excited intermediate states. Based on this, in arXiv:2311.01339 we elucidate two pathways: (i) In the absence of external driving, long-range interactions are mediated by the exchange of at least two virtual cavity photons. We show that these vacuum-mediated interactions can surpass local Heisenberg interactions in mesoscopic setups, e.g., in small enough split-ring resonators. (ii) In a laser-driven cavity, interactions can be tailored through a hybrid scheme of both laser and cavity photons. This offers a versatile pathway for Floquet engineering of long-range interactions in macroscopic systems. In general, the derivation of these interactions requires careful consideration: We demonstrate that a simple phenomenological approach, based on an effective spin-photon Hamiltonian, can be used only if the cavity is resonantly driven. Outside of these narrow regimes and for the undriven case, a series expansion within the underlying electronic model is necessary, which we perform to obtain long-range four-spin interactions in the half-filled Hubbard model.

Keywords: Cavity quantum electrodynamics; Light-matter interaction; Hubbard model; Floquet engineering; Exchange interaction