Superfluid and Mott-insulator phases of one-dimensional Bose-Fermi mixtures

Abstract

We study the ground state phases of Bose-Fermi mixtures in one-dimensional optical lattices with quantum Monte Carlo simulations using the canonical worm algorithm. Depending on the filling of bosons and fermions, and the on-site intra-and interspecies interaction, different kinds of incompressible and superfluid phases appear. On the compressible side, correlations between bosons and fermions can lead to a distinctive behavior of the bosonic superfluid density and the fermionic stiffness, as well as of the equal-time Green functions, which allow one to identify regions where the two species exhibit anticorrelated flow. We present here complete phase diagrams for these systems at different fillings and as a function of the interaction parameters.

Feshbach-Einstein Condensates

“…Moreover, the inset shows that the correlated superfluid density ρ cor s vanishes as the system size increases, as expected for an insulating phase. However we can see that the superfluid densities associated with the individual atomic and molecular species converge to a finite value, which is the signature of a SM phase (a similar phase is also present in the case of Bose-Fermi mixtures [15]). This is the first qualitative difference between MF results and ours.…”

Effects of a single fermion in a Bose Josephson junction

“…These have been studied mostly on the mean-field level by solving nonlinear Schrödinger equations for one [10] or two wells [11] or by compositefermion methods on an optical lattice [12][13][14]. Phase diagrams have been computed for Bose-Fermi mixtures in three [15] or one dimensions [16][17][18].…”

Generalized dynamical mean-field theory for Bose-Fermi mixtures in optical lattices

“…At the same time the bosonic species can be superfluid, allowing for supersolid behavior, where diagonal CDW order coexists with off-diagonal superfluid long-range order. Several previous theoretical works have studied mixtures of fermions and bosons in an optical lattice 28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47 . In some of these 34,35,36,37,38 supersolid phases were predicted.…”

“…In one dimension this involved bosonization 36 , Density Matrix Renormalization Group 30,33 , and Quantum Monte Carlo 38,39,40,41,42,43 . In higher dimensions, however, non-perturbative calculations are sparse.…”