Sommaire:

In this talk, I will discuss the issue of gauge fixing for strongly correlated electrons coupled to quantum light, described by projected low-energy models such as those obtained within tight-binding methods. I will present a formalism that allows one to write down the Hamiltonian of correlated electrons coupled to photons in the dipole and Coulomb gauges which remain fully equivalent, i.e., related by a unitary transformation. I will discuss the relation between this approach and the so called Peierls substitution, often used to describe light-matter coupling in tight-binding models. I will apply proposed formalism to a two-band model for an excitonic insulator coupled to a uniform cavity mode. In the dipole gauge the absence of superradiance beyond mean-field theory is confirmed, in accordance with the recent no-go theorem. Furthermore, the excitation spectrum of the model contains non-trivial light-matter entanglement in the form of polariton modes. I will show that the polariton spectrum is the same within the projected dipole and Coulomb gauge, a further demonstration of gauge equivalence. Moreover, I will show that by applying the proposed formalism to a model presenting topological behavior allows for controlling its topological phase transition point.

Pour plus d'informations, merci de contacter Antezza M.