We consider a model of free fermions in a ladder geometry coupled to a non-uniform cavity mode via Peierls substitution. Since the cavity mode generates a magnetic field, no-go theorems on spontaneous photon condensation do not apply, and we indeed observe a phase transition to a photon condensed phase characterized by finite circulating currents, alternatively referred to as the equilibrium superradiant phase. We consider both square and triangular ladder geometries, and characterize the transition by studying the energy structure of the system, light-matter entanglement, the properties of the photon mode, and chiral currents. The transition is of first order and corresponds to a sudden change in the fermionic band structure as well as the number of its Fermi points. Thanks to the quasi-one dimensional geometry we scrutinize the accuracy of (mean field) cavity-matter decoupling against large scale density-matrix renormalization group simulations. We find that light-matter entanglement is essential for capturing corrections to matter properties at finite sizes and for the description of the correct photon state. The latter remains Gaussian in the the thermodynamic limit both in the normal and photon condensed phases.
Authors / Affiliations: mappings to Contributors and OrganizationsSee all Organizations.
- 1 2 Zeno Bacciconi,
- 3 Gian Marcello Andolina,
- 1 Titas Chanda,
- 1 2 Giuliano Chiriacò,
- 3 Marco Schirò,
- 1 2 Marcello Dalmonte
- 1 Centro Internazionale di Fisica Teorica Abdus Salam / Abdus Salam International Centre for Theoretical Physics [ICTP]
- 2 Scuola Internazionale Superiore di Studi Avanzati / International School for Advanced Studies [SISSA]
- 3 Collège de France
- European Research Council [ERC]
- Horizon 2020 (through Organization: European Commission [EC])
- Infrastruktura PL-Grid
- Ministero dell’Istruzione, dell’Università e della Ricerca (MIUR) (through Organization: Ministero dell'Istruzione, dell'Università e della Ricerca / Ministry of Education, Universities and Research [MIUR])