Research Project: Aşırı Soğuk Kuvantum Gazları ile Kuvvetl,ce İlişkili Yoğun Madde Olayları
Loading...
Contributors
Funders
ID
TB.00047
Authors
Işkın, Menderes
Faculty Member
Publications
Vortex line in spin-orbit coupled atomic Fermi gases
(American Physical Society (APS), 2012) Işkın, Menderes; Department of Physics; Yes; College of Sciences
It has recently been shown that the spin-orbit coupling gives rise to topologically nontrivial and thermodynamically stable gapless superfluid phases when the pseudospin populations of an atomic Fermi gas are imbalanced, with the possibility of featuring Majorana zero-energy quasiparticles. In this paper, we consider a Rashba-type spin-orbit coupling, and use the Bogoliubov-de Gennes formalism to analyze a single vortex line along a finite cylinder with a periodic boundary condition. We show that the signatures for the appearance of core-and edge-bound states can be directly found in the density of single-particle states and particle-current density. In particular, we find that the pseudospin components counterflow near the edge of the cylinder, the strength of which increases with increasing spin-orbit coupling.
Route to supersolidity for the extended Bose-Hubbard model
(American Physical Society (APS), 2011) Işkın, Menderes; Department of Physics; Yes; College of Sciences
We use the Gutzwiller ansatz and analyze the phase diagram of the extended Bose-Hubbard Hamiltonian with on-site (U) and nearest-neighbor (V ) repulsions. For d-dimensional hypercubic lattices, when 2dV < U, it is well known that the ground state alternates between the charge-density-wave (CDW) and Mott insulators, and the supersolid (SS) phase occupies small regions around the CDW insulators. However, when 2dV > U, in this Rapid Communication, we show that the ground state has only CDW insulators, and more importantly, the SS phase occupies a much larger region in the phase diagram, existing up to very large hopping values which could be orders of magnitude higher than that of the well-known case. In particular, the SS-superfluid phase boundary increases linearly as a function of hopping when 2dV 1.5U, for which the prospects of observing the SS phase with dipolar Bose gases loaded into optical lattices is much higher.
Trapped Fermi gases with Rashba spin-orbit coupling in two dimensions
(American Physical Society (APS), 2012) Işkın, Menderes; Department of Physics; Yes; College of Sciences
Here we consider both balanced and imbalanced Fermi gases throughout the BCS-BEC evolution, and we study the effects of spin-orbit coupling (SOC) on the spontaneously induced countercirculating mass currents and the associated intrinsic angular momentum via the Bogoliubov-de Gennes (BdG) formalism. In particular, we find that even a small SOC destabilizes Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) type spatially modulated superfluid phases and phase-separated states against the polarized superfluid phase. We also show that the continuum of the quasiparticle and quasihole excitation spectrum can be connected by zero, one, or two discrete branches of interface modes, depending on the number of interfaces between a topologically trivial phase and a nontrivial phase.
Artificial gauge fields for the Bose-Hubbard model on a checkerboard superlattice and extended Bose-Hubbard model
(Springer, 2012) Işkın, Menderes; Department of Physics; Yes; College of Sciences
We study the effects of an artificial gauge field on the ground-state phases of the Bose-Hubbard model on a checkerboard superlattice in two dimensions, including the superfluid phase and the Mott and alternating Mott insulators. First, we discuss the single-particle Hofstadter problem, and show that the presence of a checkerboard superlattice gives rise to a magnetic flux-independent energy gap in the excitation spectrum. Then, we consider the many-particle problem, and derive an analytical mean-field expression for the superfluid-Mott and superfluid-alternating-Mott insulator phase transition boundaries. Finally, since the phase diagram of the Bose-Hubbard model on a checkerboard superlattice is in many ways similar to that of the extended Bose-Hubbard model, we comment on the effects of magnetic field on the latter model, and derive an analytical mean-field expression for the superfluid-insulator phase transition boundaries as well.
Quantum phases of atomic Fermi gases with anisotropic spin-orbit coupling
(American Physical Society (APS), 2011) Işkın, Menderes; Subaşı, A. L.; Department of Physics; Yes; College of Sciences
We consider a general anisotropic spin-orbit coupling and analyze the phase diagrams of both balanced and imbalanced Fermi gases for the entire BCS-BEC evolution. In the first part, we use the self-consistent mean-field theory at zero temperature, and show that the topological structure of the ground-state phase diagrams is quite robust against the effects of anisotropy. In the second part, we go beyond the mean-field description, and investigate the effects of Gaussian fluctuations near the critical temperature. This allows us to derive the time-dependent Ginzburg-Landau theory, from which we extract the effective mass of the Cooper pairs and their critical condensation temperature in the molecular BEC limit.
