Eur. Phys. J. B 72, 25-39 (2009)
https://doi.org/10.1140/epjb/e2009-00321-2

The electromagnetic response of a fermion system at zero temperature

¹ Department of Physics, University of Stellenbosch Private Bag X1, Matieland 7602, Stellenbosch, South Africa
² Faculty of Pharmacy, Collegium Medicum in Bydgoszcz Nicolaus Copernicus University in Toruń, ul. Jagiellońska 13, 85-067 Bydgoszcz, Poland

Corresponding author: ^a fornal@cm.umk.pl

Received: 16 June 2008
Revised: 7 February 2009
Published online: 26 September 2009

Abstract

An investigation is shown whether the Meissner-Ochsenfeld effect exists in a gas of spin 1/2 fermions in which an attraction (denoted by W) between particles having the same momenta and opposite spins as well as a BCS type four-fermion interaction between pairs are present in a system. The former potential is equivalent to the effective kinetic energy of free fermion pairs. The latter interaction (denoted by V₄) is responsible for the presence of fermion quadruples in the system. The Meissner effect proves to be weaker than in BCS theory, implying a larger penetration depth λ of the external magnetic field in the regime of the weak attraction W; however, this effect turns out to exist even when the gap parameter of quadruples vanishes. In this regime the strength of the Meissner effect is the same as in the BCS case.