Magnetic phase transition in coherently coupled Bose gases in optical lattices

Year: 2016

Authors: Barbiero L., Abad M., Recati A.

Autors Affiliation: Univ Padua, Dipartimento Fis & Astron Galileo Galiei, I-35131 Padua, Italy; Univ Trento, CNR, INO, BEC Ctr, I-38123 Povo, Italy; Univ Trento, Dipartimento Fis, I-38123 Povo, Italy; OIST Grad Univ, Quantum Syst Unit, Onna, Okinawa 9040495, Japan; Tech Univ Munich, James Franck Str 1, D-85748 Garching, Germany

Abstract: We describe the ground state of a gas of bosonic atoms with two coherently coupled internal levels in a deep optical lattice in a one-dimensional geometry. In the single-band approximation this system is described by a Bose-Hubbard Hamiltonian. The system has a superfluid and a Mott insulating phase that can be either paramagnetic or ferromagnetic. We characterize the quantum phase transitions at unit filling by means of a density-matrix renormalization-group technique and compare the results with a mean-field approach and an effective spin Hamiltonian. The presence of the ferromagnetic Ising-like transition modifies the Mott lobes. In the Mott insulating region the system maps to the ferromagnetic spin-1/2 XXZ model in a transverse field and the numerical results compare very well with the analytical results obtained from the spin model. In the superfluid regime quantum fluctuations strongly modify the phase transition with respect to the well-established mean-field three-dimensional classical bifurcation.


Volume: 93 (3)      Pages from: 033645-1  to: 033645-6

More Information: Useful discussions with G. Ferrari, Yan-Hua Hou, and Tommaso Roscilde are acknowledged. This work was supported by ERC through a QGBE grant and by Provincia Autonoma di Trento. L.B. acknowledges support from the Cariparo Foundation (Eccellenza Grant No. 11/12) and the CNR-INO BEC Center in Trento for CPU time. A.R. acknowledges support from the Alexander von Humboldt Foundation. M.A. acknowledges support from the Okinawa Institute of Science and Technology Graduate University during the final stages of the work.
KeyWords: Coherently Coupled Bose gases, Bose-Hubbard Models, Quantum Magnetism
DOI: 10.1103/PhysRevA.93.033645

Citations: 9
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