Group Seminar Dynamics of Correlated Quantum Matter: "Cavity induced long-range interaction in strongly correlated system”

by Mr Paul Fadler (University of Erlangen-Nürnberg)

Wednesday 21 Jun 2023, 16:00 → 17:30 Europe/Berlin

4064 (Campus Bahrenfeld)

Cavity induced long-range interaction in

strongly correlated systems

 

 

In Floquet engineering of quantum systems it is not possible to engineer long-range interactions through driving with classical fields. With quantum fields, such as the electromagnetic field of an optical cavity, one can engineer long-range interactions [1,2]. Local couplings can create excitations of the field, that are able to propagate long ranges before being reabsorbed. The field therefore acts as mediator for long-range processes.

We investigate such interactions for a correlated Fermi-Hubbard system coupled to the electromagnetic field of a cavity. In the Fermi-Hubbard model at half filling we find cavity mediated magnetic long-range interactions in terms of four-spin interactions. They are reliant on two energy scales: that of cavity fluctuations ω and that of charge excitations U. We derive them either through the elimination of the cavity from an effective spin-photon Hamiltonian [3] or through the simultaneous elimination of both cavity and charge fluctuations.

We show that the former and much simpler approach fails if the energy scales do not separate as ω≫U. Hybrid charge-cavity excitations are not properly contained leading to unphysical divergences. The simultaneous elimination of both types of fluctuations is, however, capable of reproducing the long-range interactions. Finally, we show that an additional classical drive can enhance the interactions such that they contribute in the thermodynamic limit. If detunings are properly chosen, it can furthermore recover the simple dynamics of the spin-photon Hamiltonian based description.

 

[1] F. Schlawin, A. Cavalleri, D. Jaksch, Phys. Rev. Lett. 122, 133602 (2019)

[2] A. Chiocchetta, D. Kiese, C.P. Zelle, F. Piazza, S. Diehl, Nat Commun 12, 5901 (2021)

[3] M.A. Sentef, J. Li, F. Künzel, M. Eckstein, Phys. Rev. Research 2, 033033 (2020)