Three-Body Collective Excitations in the Superconducting Phase of $MgB_2$

TL;DR

This paper investigates the collective three-body excitations in the superconducting phase of MgB2, highlighting the role of strong two-phonon-electron coupling and the emergence of gapped three-fermion states affecting thermodynamics.

Contribution

It introduces the concept of three-body collective excitations in MgB2 superconductors resulting from strong two-phonon-electron interactions, a novel theoretical insight.

Findings

Identification of three-body spin-1/2 fermion excitations

Gapped fermionic states influenced by single fermion gaps

Implications for thermodynamic properties of MgB2

Abstract

It is shown that coherent behavior of Cooper's pairs and electrons in the two-band superconductors $MgB_2$ is possible as a result of a strong two-phonon-electron coupling. The spin-$\frac 12$ triples with zero angular momentum are made up of three spin-$\frac 12$ fermions with charge $\emph{e}$. They are gapped Fermi excitations with gap induced by the gaps of the single fermions. Their contribution to the thermodynamics of the $MgB_2$ superconductors is considered.