Publications
Core filling and snaking instability of dark solitons in spin-imbalanced superfluid Fermi gases
We use the time-dependent Bogoliubov-de Gennes equations to study dark solitons in three-dimensional spin-imbalanced superfluid Fermi gases. We explore how the shape and dynamics of dark solitons are altered by the presence of excess unpaired spins which fill their low-density core. The unpaired particles broaden the solitons and suppress the transverse snake instability. We discuss ways of observing these phenomena in cold-atom experiments. © 2017 American Physical Society.
Cooling quantum gases with entropy localization
We study the dynamics of entropy in a time dependent potential and explore how disorder influences this entropy flow. We show that disorder can trap entropy at the edge of the atomic cloud enabling a novel cooling method. We demonstrate the feasibility of our cooling technique by analyzing the evolution of entropy in a one-dimensional Fermi lattice gas with a time dependent superlattice potential. © 2017 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
Dimensional crossover in a spin-imbalanced Fermi gas
We model the one-dimensional (1D) to three-dimensional (3D) crossover in a cylindrically trapped Fermi gas with attractive interactions and spin imbalance. We calculate the mean-field phase diagram and study the relative stability of exotic superfluid phases as a function of interaction strength and temperature. For weak interactions and low density, we find 1D-like behavior, which repeats as a function of the chemical potential as new channels open. For strong interactions, mixing of single-particle levels gives 3D-like behavior at all densities.
Nonequilibrium fractional Hall response after a topological quench
We theoretically study the Hall response of a lattice system following a quench where the topology of a filled band is suddenly changed. In the limit where the physics is dominated by a single Dirac cone, we find that the change in the Hall conductivity is two-thirds of the quantum of conductivity. We explore this universal behavior in the Haldane model and discuss cold-atom experiments for its observation. Beyond the linear response, the Hall effect crosses over from fractional to integer values. We investigate finite-size effects and the role of harmonic confinement.
Lattice bosons with infinite-range checkerboard interactions
Motivated by experiments performed by Landig et al. [Nature (London) 532, 476 (2016)NATUAS0028-083610.1038/nature17409], we consider a two-dimensional Bose gas in an optical lattice, trapped inside a single mode superradiant Fabry-Perot cavity. The cavity mediates infinite-range checkerboard interactions between the atoms, which produces competition between Mott insulator, charge-density wave, superfluid, and supersolid phases. We calculate the phase diagram of this Bose gas in a homogeneous system and in the presence of a harmonic trap. © 2016 American Physical Society.
Observation of a new superfluid phase for 3He embedded in nematically ordered aerogel
In bulk superfluid 3He at zero magnetic field, two phases emerge with the B-phase stable everywhere except at high pressures and temperatures, where the A-phase is favoured. Aerogels with nanostructure smaller than the superfluid coherence length are the only means to introduce disorder into the superfluid. Here we use a torsion pendulum to study 3He confined in an extremely anisotropic, nematically ordered aerogel consisting of ∼410 nm-thick alumina strands, spaced by ∼100 nm, and aligned parallel to the pendulum axis.
Disappearance of quasiparticles in a Bose lattice gas
We use a momentum-space hole-burning technique implemented via stimulated Raman transitions to measure the momentum relaxation time for a gas of bosonic atoms trapped in an optical lattice. By changing the lattice potential depth, we observe a smooth crossover between relaxation times larger and smaller than the bandwidth. The latter condition violates the Mott-Ioffe-Regel bound and indicates a breakdown of the quasiparticle picture. We produce a simple kinetic model that quantitatively predicts these relaxation times.
Competing ground states of strongly correlated bosons in the Harper-Hofstadter-Mott model
Using an efficient cluster approach, we study the physics of two-dimensional lattice bosons in a strong magnetic field in the regime where the tunneling is much weaker than the on-site interaction strength. We study both the dilute, hard-core bosons at filling factors much smaller than unity occupation per site and the physics in the vicinity of the superfluid-Mott lobes as the density is tuned away from unity. For hard-core bosons, we carry out extensive numerics for a fixed flux per plaquette φ=1/5 and φ=1/3.
Dynamics of pattern-loaded fermions in bichromatic optical lattices
Motivated by experiments in Munich [M. Schreiber et al., Science 349, 842 (2015).SCIEAS0036-807510.1126/science.aaa7432], we study the dynamics of interacting fermions initially prepared in charge density wave states in one-dimensional bichromatic optical lattices.
Proposal to directly observe the Kondo effect through enhanced photoinduced scattering of cold fermionic and bosonic atoms
We propose an experimental protocol to directly observe the Kondo effect by scattering ultracold atoms. We propose using an optical Feshbach resonance to engineer Kondo-type spin-dependent interactions in a system with ultracold Li6 and Rb87 gases. We calculate the momentum transferred from the Rb87 gas to the Li6 gas in a scattering experiment and show that it has a logarithmically enhanced temperature dependence, characteristic of the Kondo effect, and analogous to the resistivity of alloys with magnetic impurities.