Speaker
Description
A simplified mean-field description of fermionic systems relies on the Hartree-Fock-
Bogoliubov (HFB) approach, where the two-particle interaction is decomposed into
three distinct channels. A major issue with this method is that the separation between
the channels is somewhat arbitrary. Depending on the physical situation to be
described, different channels turn out to be important.
In this poster, we present a self-consistently generalized mean-field theory, which is
based on introducing a separate weighting factor for each channel. This ansatz
removes the arbitrariness of the channel separation by providing an extremization
principle for their optimal partitioning.
The power of our technique is illustrated by considering the example of two
unpolarized fermionic species with contact interaction. In this case the Fock
contribution vanishes and we obtain a coupling between the Hartree and the
Bogoliubov channel. This results non only in first beyond mean-field corrections[1,2]
already at the mean-field but also decreases the critical temperature in qualitative
agreement to particle-hole fluctuations [3]. Due to the non-perturbative nature of the
channel coupling we also obtain results which are not captured by any fluctuation
theory in one channel alone. This requires the introduction of an effective interaction
range as a new length scale and should become relevant for large enough densities.
With this our formalism builds a natural theoretical bridge between fermionic
superfluidity in ultracold atomic gases and superconductivity in condensed matter
physics as well as the realm of nuclei and neutron matter.strong text
References
[1] C. A. R. Sá de Melo, M. Randeria, J. R. Engelbrecht, Phys. Rev. Lett. 71,
3202 (1993)
[2] J. R. Engelbrecht, M. Randeria and C. A. R. Sá de Melo, Phys. Rev. B 55,
15153 (1997)
[3] L. Gor’Kov and T. Melik-Barkhudarov, Sov. Phys. JETP 13, 1018 (1961)
Short bio (50 words) or link to website
https://www-user.rhrk.uni-kl.de/~apelster
| Career stage | Postdoc |
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