The Symmetry of Pairing and The Electromagnetic Properties of A Superconductor with A Four-Fermion Attraction at Zero Temperature

Przemyslaw Tarasewicz

doi:10.3390/sym11111358

Abstract

Properties of a fermion system at zero temperature are investigated. The physical system is described by a Hamiltonian containing the BCS interaction and an attractive four-fermion interaction. The four-fermion potential is caused by attractions between Cooper pairs mediated by the phonon field. In this paper, the BCS interaction is assumed to be negligible and the four-fermion potential is the only one that acts in the system. The effect of the pairing symmetry used in the four-fermion potential on some zero-temperature properties is studied. This especially concerns the electromagnetic response of the system to an external magnetic field. It turns out that, in this instance, there are serious differences between the conventional BCS system and the one investigated in this paper.

Highlights

Recent decades have been witnessing many new phenomena discovered in solid-state physics
Our objective is to demonstrate the existence of the Meissner–Ochsenfeld effect in the system described by the Hamiltonian H f = Hg + H 0, where H 0 represents the perturbation due to a weak static external electromagnetic field described by the vector potential A(r)
The system with the four-fermion attraction has been investigated in this paper

Summary

Introduction

Recent decades have been witnessing many new phenomena discovered in solid-state physics (e.g., high temperature superconductivity, heavy fermion superconductors and unusual properties of 3 He) These discoveries are intriguing and lead to many new questions on the nature of superconductivity and superfluidity. We still do not know how many particles are engaged in constituting the fundamental clusters responsible for the occurrence of new phases Is it possible that only two-particle entities are relevant to these systems (e.g., Cooper pairs) or may three or four-particle structures be taken into account? Let us start with a work by Schneider and Keller [2] who measured the relationship between the critical temperature and zero temperature condensate density for some cuprates and Chevrel-phases superconductors They noticed that the experimental data for YBa2 Cu3 O6.602 , for example, ca be associated with the behavior of a dilute Bose gas. Two papers [5,6] reported on a discovery of the half-h/2e magnetic flux quanta coexisting together with the usual ones in SQUIDs fabricated

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