20 research outputs found
Few vs many-body physics of an impurity immersed in a superfluid of spin 1/2 attractive fermions
In this article we investigate the properties of an impurity immersed in a
superfluid of strongly correlated spin 1/2 fermions. For resonant interactions,
we first relate the stability diagram of dimer and trimer states to the
three-body problem for an impurity interacting with a pair of fermions. Then we
calculate the beyond-mean-field corrections to the energy of a weakly
interacting impurity. We show that these corrections are divergent and have to
be regularized by properly accounting for three-body physics in the problem
Momentum distribution of a dilute unitary Bose gas with three-body losses
Using Boltzmann's equation, we study the effect of three-body losses on the
momentum distribution of a homogeneous unitary Bose gas in the dilute limit
where quantum correlations are negligible. We calculate the momentum
distribution of the gas and show that inelastic collisions are quantitatively
as important as a second order virial correction.Comment: 4 pages + supplemental materia
Hydrodynamic spectrum of a superfluid in an elongated trap
--In this article we study the hydrodynamic spectrum of a superfluid confined
in a cylindrical trap. We show that the dispersion relation (q) of the
phonon branch scales like \sqrt q at large q, leading to a vanishingly small
superfluid critical velocity. In practice the critical velocity is set by the
breakdown of the hydrodynamic approximation. For a broad class of superfluids,
this entails a reduction of the critical velocity by a factor (
/\"i1/2c) 1/3 with respect to the free-space prediction (here
is the trapping frequency and \"i1/2c the chemical potential of the cloud)
Condensation Energy of a Spin-1/2 Strongly Interacting Fermi Gas
We report a measurement of the condensation energy of a two-component Fermi
gas with tunable interactions. From the equation of state of the gas, we infer
the properties of the normal phase in the zero-temperature limit. By comparing
the pressure of the normal phase at T=0 to that of the low-temperature
superfluid phase, we deduce the condensation energy, i.e. the energy gain of
the system in being in the superfluid rather than normal state. We compare our
measurements to a ladder approximation description of the normal phase, and to
a fixed node Monte-Carlo approach, finding excellent agreement. We discuss the
relationship between condensation energy and pairing gap in the BEC-BCS
crossover.Comment: 4 figure
Second-order virial expansion for an atomic gas in a harmonic waveguide
International audienceThe virial expansion for cold two-component Fermi and Bose atomic gases is considered in the presence of a waveguide and in the vicinity of a Feshbach resonance. The interaction between atoms and the coupling with the Feshbach molecules is modeled using a quantitative separable two-channel model. The scattering phase-shift in an atomic waveguide is defined. This permits us to extend the Beth-Uhlenbeck formula for the second-order virial coefficient to this inhomogeneous case
Current noise through a Kondo quantum dot in a SU(N) Fermi liquid state
The current noise through a mesoscopic quantum dot is calculated and analyzed
in the Fermi liquid regime of the SU(N) Kondo model. Results connect the
Johnson-Nyquist noise to the shot noise for an arbitrary ratio of voltage and
temperature, and show that temperature corrections are sizeable in usual
experiments. For the experimentally relevant SU(4) case, quasiparticle
interactions are shown to increase the shot noise.Comment: 4 pages, 2 figures, to be published in Phys. Rev. Lett. (revised
version