title: Dicke-type phase transition in a spin-orbit-coupled Bose-Einstein condensate.
abstract: Spin-orbit-coupled Bose-Einstein condensates (BECs) provide a powerful tool to investigate interesting gauge field-related phenomena. Here we study the ground state properties of such a system and show that it can be mapped to the well-known Dicke model in quantum optics, which describes the interactions between an ensemble of atoms and an optical field. A central prediction of the Dicke model is a quantum phase transition between a superradiant phase and a normal phase. We detect this transition in a spin-orbit-coupled BEC by measuring various physical quantities across the phase transition. These quantities include the spin polarization, the relative occupation of the nearly degenerate single-particle states, the quantity analogous to the photon field occupation and the period of a collective oscillation (quadrupole mode). The applicability of the Dicke model to spin-orbit-coupled BECs may lead to interesting applications in quantum optics and quantum information science.
authors.affiliation: Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, USA.
authors.forename: Chris
authors.initials: C
authors.lastname: Hamner
authors.affiliation: Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080, USA.
authors.forename: Chunlei
authors.initials: C
authors.lastname: Qu
authors.affiliation: 1] Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, USA [2] Quantum System Unit, Okinawa Institute of Science and Technology, Okinawa 904-0495, Japan.
authors.forename: Yongping
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, USA.
authors.forename: JiaJia
authors.initials: J
authors.lastname: Chang
authors.affiliation: 1] Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080, USA [2] Department of Physics and Center of Coherence, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Gong
authors.affiliation: 1] Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, USA [2] Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080, USA.
authors.forename: Chuanwei
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Engels