Effect of Disorder on the Interacting Fermi Gases in a One-Dimensional Optical Lattice (original) (raw)
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Interacting Fermi gases in disordered one-dimensional lattices
Physical Review B, 2006
Interacting two-component Fermi gases loaded in a one-dimensional (1D) lattice and subject to harmonic trapping exhibit intriguing compound phases in which fluid regions coexist with local Mottinsulator and/or band-insulator regions. Motivated by experiments on cold atoms inside disordered optical lattices, we present a theoretical study of the effects of a random potential on these groundstate phases. Within a density-functional scheme we show that disorder has two main effects: (i) it destroys the local insulating regions if it is sufficiently strong compared with the on-site atom-atom repulsion, and (ii) it induces an anomaly in the compressibility at low density from quenching of percolation.
Ground-state phases of interacting Fermi gases in disordered one-dimensional lattices
Journal of Physics B: Atomic, Molecular and Optical Physics, 2012
Interacting two-component Fermi gases loaded in a one-dimensional ͑1D͒ lattice and subject to harmonic trapping exhibit intriguing compound phases in which fluid regions coexist with local Mott-insulator and/or band-insulator regions. Motivated by experiments on cold atoms inside disordered optical lattices, we present a theoretical study of the effects of a random potential on these ground-state phases. Within a densityfunctional scheme we show that disorder has two main effects: ͑i͒ it destroys the local insulating regions if it is sufficiently strong compared with the on-site atom-atom repulsion, and ͑ii͒ it induces an anomaly in the compressibility at low density from quenching of percolation.
Phase behaviors of strongly correlated Fermi gases in one-dimensional confinements
Laser Physics, 2007
We report on the ground state of models for strongly correlated one-dimensional Fermi systems by means of theoretical studies of two-component atomic Fermi gases in highly anisotropic harmonic traps. In this context, we consider (i) the Gaudin-Yang model for a Luttinger liquid with repulsive interactions, including an analysis of the emergence of Wigner molecules in the 2 k F 4 k F crossover, and (ii) the lattice Hubbard model yielding Luttinger liquid and Mott insulator or band-insulator phases for repulsive interactions and the Luther-Emery phase for attractive interactions, including in the former case an analysis of the role of disorder. Our calculations use novel versions of density and spin-density functional theory and a density-matrix renormalization-group technique. We also discuss preliminary results and future perspectives in the study of nonsymmetric two-component Fermi gases.
Two-Component Fermi Gas on Internal-State-Dependent Optical Lattices
Physical Review Letters, 2005
We study the phase diagram of one dimensional spin-1 2 fermionic cold atoms. The two "spin" species can have different hopping or mass. The phase diagram at equal densities of the species is found to be very rich, containing Mott insulators and superfluids. We also briefly discuss coupling 1D systems together, and some experimental signatures of these phases. In particular, we compute the spin structure factor for small momentum, which should allow the spin gap to be detected.
Random on-site interactions versus random potential in ultra cold atoms in optical lattices
Applied Physics B, 2006
We consider the physics of lattice bosons in the presence of either disordered on-site chemical potential or disordered on-site interparticle interactions. By means of analytical results using strong-coupling expansion, and numerical results based on quantum Monte Carlo calculations, we show that important qualitative changes in the zero temperature phase diagram are observed when comparing both cases. Although for both types of disorder superfluid, Mott-insulator and Bose-glass phases may be found, we show that in the case of random interactions the Mott-insulating regions shrink and eventually vanish for any finite disorder strength beyond a sufficiently large filling factor. Furthermore, at low values of the chemical potential both the superfluid and Mott insulator are stable towards the formation of a Bose-glass, leading to a possibly non-trivial tricritical point. We discuss possible experimental realizations of both types of disorder in the context of ultra cold atomic gases in optical lattices.
Thermodynamic properties of correlated fermions in lattices with spin-dependent disorder
New Journal of Physics, 2013
Motivated by the rapidly growing possibilities for experiments with ultracold atoms in optical lattices, we investigate the thermodynamic properties of correlated lattice fermions in the presence of an external spindependent random potential. The corresponding model, a Hubbard model with spin-dependent local random potentials, is solved within dynamical mean-field theory. This allows us to present a comprehensive picture of the thermodynamic properties of this system. In particular, we show that for a fixed total number of fermions spin-dependent disorder induces a magnetic polarization. The magnetic response of the polarized system differs from that of a system with conventional disorder.
We investigate the static and dynamical behavior of 1D interacting fermions in disordered Hubbard chains, contacted to semi-infinite leads. The chains are described via the repulsive Anderson-Hubbard Hamiltonian, using static and time-dependent lattice density-functional theory. The dynamical behavior of our quantum transport system is performed via an integration scheme available in the literature, which we modify via the recursive Lanczos method, to increase its efficiency. To quantify the degree of localization due to disorder and interactions, we adapt the definition of the inverse participation ratio to obtain an indicator which is both suitable for quantum transport geometries and which can be obtained within density-functional theory. Lattice density functional theories are reviewed and, for contacted chains, we analyze the merits and limits of the coherentpotential approximation in describing the spectral properties, with interactions included via lattice density functional theory. Our approach appears to able to capture complex features due to the competition between disorder and interactions. Specifically, we find a dynamical enhancement of delocalization in presence of a finite bias, and an increase of the steady-state current induced by inter-particle interactions. This behavior is corroborated by results for the time-dependent densities and for the inverse participation ratio. Using short isolated chains with interaction and disorder, a brief comparative analysis between time-dependent density-functional theory and exact results is then given, followed by general conclusive remarks.
Strongly correlated Fermi–Bose mixtures in disordered optical lattices
Journal of Physics B: Atomic, Molecular and Optical Physics, 2006
We investigate theoretically the low-temperature physics of a two-component ultracold mixture of bosons and fermions in disordered optical lattices. We focus on the strongly correlated regime. We show that, under specific conditions, composite fermions, made of one fermion plus one bosonic hole, form. The composite picture is used to derive an effective Hamiltonian whose parameters can be controlled via the boson-boson and the bosonfermion interactions, the tunnelling terms and the inhomogeneities. We finally investigate the quantum phase diagram of the composite fermions and show that it corresponds to the formation of Fermi glasses, spin glasses and quantum percolation regimes.
Phase diagram of imbalanced strongly interacting fermions on a one-dimensional optical lattice
Physical Review A, 2009
We show that the Hubbard Hamiltonian with particle-assisted tunneling rates -recently proposed to model a fermionic mixture near a broad Feshbach resonance-displays a ground state phase diagram with superfluid, insulating, and phase separated regimes. In the latter case, when the populations are balanced the two phases coexist in microscopic antiferromagnetic domains. Macroscopic phase segregation into a high-density superfluid of molecules, and a low-density Fermi liquid of single atoms appears in the density profile above a critical polarization pc.
Collective Excitations of an Imbalanced Fermion Gas in a 1D Optical Lattice
Journal of Low Temperature Physics, 2014
The collective excitations that minimize the Helmholtz free energy of a population-imbalanced mixture of a 6 Li gas loaded in a quasi one-dimensional optical lattice are obtained. These excitations reveal a rotonic branch after solving the Bethe-Salpeter equation under a generalized random phase approximation based on a singleband Hubbard Hamiltonian. The phase diagram describing stability regions of Fulde-Ferrell-Larkin-Ovchinnikov and Sarma phases is also analyzed.