arXiv:1110.1188 · Physical Review Letters

Suppression of Superfluidity upon Overflow of Trapped Fermions: Quantal and Thomas-Fermi Studies

Peter Schuck, X. Viñas

Published Nov 7, 2011• 11 citations

Abstract

Two issues are treated in this work. (i) The generic fact that, if a fermionic superfluid in the BCS regime overflows from a narrow container into a much wider one, pairing is much suppressed at the overflow point. Physical examples where this feature may play an important role are discussed. (ii) A Thomas-Fermi approach to inhomogeneous superfluid Fermi systems is presented and shown to work well in cases where the local density approximation breaks down.

DOI: 10.1103/physrevlett.107.205301

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arXiv:1110.1188 · Physical Review Letters

Suppression of Superfluidity upon Overflow of Trapped Fermions: Quantal and Thomas-Fermi Studies

Peter Schuck, X. Viñas

Published Nov 7, 2011• 11 citations

arXiv HTML PDF

Abstract

DOI: 10.1103/physrevlett.107.205301

Related papers

Suppression of Superfluidity upon Overflow of Trapped Fermions. Quantal and Thomas-Fermi Studies

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Two issues will be discussed in this contribution: (i) the generic fact that if a fermionic superfluid in the BCS regime overflows from a narrow container into a much wider one, pairing is much suppressed at the overflow point. Two examples pertinent to the physics of the outer crust of neutron stars and superfluid fermionic atoms in traps will be presented, (ii) A novel Thomas-Fermi approach to inhomogeneous superfluid Fermi-systems is presented and shown that it works well in cases where the local density approximation breaks down.Two issues will be discussed in this contribution: (i) the generic fact that if a fermionic superfluid in the BCS regime overflows from a narrow container into a much wider one, pairing is much suppressed at the overflow point. Two examples pertinent to the physics of the outer crust of neutron stars and superfluid fermionic atoms in traps will be presented, (ii) A novel Thomas-Fermi approach to inhomogeneous superfluid Fermi-systems is presented and shown that it works well in cases where the local density approximation breaks down.

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(d/{R}_{\mathrm{TF}}){}^{4}

, where

d

is the oscillator length of the trap potential and

{R}_{\mathrm{TF}}

is the radial extension of the density

n

in the Thomas-Fermi approximation. In particular, at the Feshbach resonance the universal corrections to the local density approximation are calculated and a universal prefactor ${\ensuremath{\kappa}}_{W}=7/27$ is derived for the von Weizs\"acker--type correction ${\ensuremath{\kappa}}_{W}(\ensuremath{\hbar}{}^{2}/2m)({\ensuremath{\nabla}}^{2}{n}^{1/2}/{n}^{1/2})$.

T=0

, we solve the Bogoliubov--de Gennes coupled equations taking into account a Bose condensate of bound states (molecules). In the case of a broad resonance, the density profile

n(r)

, as well as the profile of the superfluid order parameter $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\Delta}}(r)$, are spatially spread out to the Thomas-Fermi radius, even in the crossover region. This order parameter $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\Delta}}(r)$ suppresses the effects of low-energy Andreev bound states on the rf tunneling current. As a result, the peak energy in the rf spectrum is found to occur at an energy equal to the superfluid order parameter $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\Delta}}(r=0)$ at the center of the trap, in contrast to the case of a narrow resonance, and in agreement with recent measurements. The local density approximation is found to give a good approximation for the rf-tunneling spectrum.