Supersolid state in fermionic optical lattice systems

Abstract

We study ultracold fermionic atoms trapped in an optical lattice with harmonic confinement by combining the real-space dynamical mean-field theory with a two-site impurity solver. By calculating the local particle density and the pair potential in the systems with different clusters, we discuss the stability of a supersolid state, where an s-wave superfluid coexists with a density-wave state of checkerboard pattern. It is clarified that a confining potential plays an essential role in stabilizing the supersolid state. The phase diagrams are obtained for several effective particle densities.Comment: 7 pages, 5 figures, Phys. Rev. A in pres

Inhomogeneous BCS-BEC crossover for trapped cold atoms in optical lattices

“…As pointed out in Ref. [15], defining a typical radius r c such that V 0 2 (r c /a) 2 = t and rescaling the density profiles in units of r c , the results for fixed μ and increasing r c , i.e., increasing N and decreasing V 0 , collapse on the same curve. Thus our results are directly relevant for current experiments in ultracold gases as they can be easily extrapolated to actual system size and number of particles.…”

“…The key approximation is to assume a local, albeit site-dependent, self-energyˆ ij =ˆ i δ ij . In order to deal with the superconducting phase, we recast the method in the Nambu spinor formalism [15], introducing anomalous (pair) Green's functions and self-energy components F i and S i , respectively. The existence of a nonzero anomalous Green's function and of a correspondent SF condensate order parameter is the fingerprint of spontaneous U (1) symmetry breaking.…”

Intersite electron correlations in a Hubbard model on inhomogeneous lattices

“…The successful development of dynamical mean field theory (DMFT) [1] enables us to investigate a wide range of heavy fermion systems. In its real-space formulation (RDMFT), it has successfully been applied to inhomogeneous systems such as quasiperiodic systems [2,3,4], fermionic cold atoms [5,6,7,8], electron systems on surfaces [9], interfaces [10,11] and topological insulating systems [12]. However, this method does not take into account intersite correlation effects, which should be important at very low temperatures.…”

Thermodynamic properties of two-component fermionic atoms trapped in a two-dimensional optical lattice

“…The observation of the magnetic-ordered phase in the optical-lattice system is a major concern for condensed matter physicists because it could provide ways to elucidate the nature of high-T c superconductors [16]. By using the recently developed real-space dynamical mean-field theory (R-DMFT) [17][18][19][20], it has been pointed out that an antiferromagnetic-(AF-) ordered phase is stable in the Hubbard model with a trapping potential at zero temperature [18]. This naturally motivates us to undertake a detailed study of both the magnetic transition and the Mott transition at finite temperatures using a reliable numerical method.…”