Nonlinear twophoton RabiHubbard model: Superradiance, photon, and photonpair BoseEinstein condensates
Abstract
We study the groundstate phase diagram of a nonlinear twophoton RabiHubbard (RH) model in one dimension using quantum Monte Carlo simulations and densitymatrix renormalizationgroup calculations. Our model includes a nonlinear photonphoton interaction term. Absent this term, the RH model has only one phase, the normal disordered phase, and suffers from spectral collapse at larger values of the photonqubit interaction or intercavity photon hopping. The photonphoton interaction, no matter how small, stabilizes the system, which now exhibits two quantum phase transitions: Normal phase to photonpair superfluid (PSF) transition and PSF to singleparticle superfluid (SPSF). The discrete Z_{4} symmetry of the Hamiltonian spontaneously breaks in two stages: First it breaks partially as the system enters the PSF and then it completely breaks when the system finally enters the SPSF phase. We show detailed numerical results supporting this, and map out the groundstate phase diagram.
 Publication:

Physical Review A
 Pub Date:
 September 2020
 DOI:
 10.1103/PhysRevA.102.033334
 arXiv:
 arXiv:2006.09412
 Bibcode:
 2020PhRvA.102c3334C
 Keywords:

 Condensed Matter  Quantum Gases;
 Condensed Matter  Other Condensed Matter;
 Quantum Physics
 EPrint:
 9 pages, 11 figures