Anna Posazhennikova

Colloquium : Weakly interacting, dilute Bose gases in 2D

This article surveys a number of theoretical problems and open questions in the field of twodimensional dilute Bose gases with weak repulsive interactions. In contrast to three dimensions, in two dimensions the formation of long-range order is prohibited by the Bogoliubov-Hohenberg theorem, and Bose-Einstein condensation is not expected to be realized. Nevertheless, the first experimental indications supporting the formation of a condensate in low dimensional systems have been recently obtained. This unexpected behaviour appears to be due to the non-uniformity introduced into a system by the external trapping potential. Theoretical predictions, made for homogeneous systems, require therefore careful reexamination. We survey a number of popular theoretical treatments of the dilute weakly interacting Bose gas and discuss their regions of applicability. The possibility of Bose-Einstein condensation in a two-dimensional gas, the validity of the perturbative t-matrix approximation and the diluteness condition are issues that we discuss in detail.

Nonequilibrium Josephson oscillations in Bose-Einstein condensates without dissipation.

We perform a detailed quantum dynamical study of nonequilibrium Josephson oscillations between interacting Bose-Einstein condensates confined in a finite-size double-well trap. We find that the Josephson junction can sustain multiple undamped Josephson oscillations up to a characteristic time scale tau(c) without quasipartcles being excited in the system. This may explain recent related experiments. Beyond a characteristic time scale tau(c) the dynamics of the junction is governed by fast, quasiparticle-assisted Josephson tunneling as well as Rabi oscillations between the discrete quasiparticle levels. We predict that an initially self-trapped state of the Bose-Einstein condensates will be destroyed by these fast dynamics.

Phonon resonances in atomic currents through Bose-Fermi mixtures in optical lattices

We present an analysis of Bose-Fermi mixtures in optical lattices for the case where the lattice potential of the fermions is tilted and the bosons (in the superfluid phase) are described by Bogoliubov phonons. It is shown that the Bogoliubov phonons enable hopping transitions between fermionic Wannier-Stark states; these transitions are accompanied by energy dissipation into the superfluid and result in a net atomic current along the lattice. We derive a general expression for the drift velocity of the fermions and find that the dependence of the atomic current on the lattice tilt exhibits negative differential conductance and phonon resonances. Numerical simulations of the full dynamics of the system based on the time-evolving block decimation algorithm reveal that the phonon resonances should be observable under the conditions of a realistic measuring procedure.

Conductance of a spin-1 quantum dot: The two-stage Kondo effect

We discuss the physics of a spin-1 quantum dot, coupled to two metallic leads, and develop a simple model for the temperature dependence of its conductance. Such quantum dots are described by a two-channel Kondo model with asymmetric coupling constants, and the spin screening of the dot by the leads is expected to proceed via a two-stage process. When the Kondo temperatures

Entanglement generation in a system of two atomic quantum dots coupled to a pool of interacting bosons

{T}_{K1}

PERIODIC HIERARCHICAL DEPOSITION

and

Thermalization of Isolated Bose-Einstein Condensates by Dynamical Heat Bath Generation

{T}_{K2}

Inflationary quasiparticle creation and thermalization dynamics in coupled Bose-Einstein condensates

of each channel are widely separated on cooling, the dot passes through a broad crossover regime

Temporal non-equilibrium dynamics of a Bose–Josephson junction in presence of incoherent excitations

{T}_{K2}⪡T⪡{T}_{K1}

Magnetic hierarchical deposition

dominated by underscreened Kondo physics. A singular or non-Fermi-liquid correction to the conductance develops in this regime. At the lowest temperatures, destructive interference between resonant scattering in both channels leads to the eventual suppression of the conductance of the dot. We develop a model to describe the growth, and ultimate suppression, of the conductance in the two channel Kondo model as it is screened successively by its two channels. Our model is based upon large-