Quasiparticle Pattern of Phenomena in Exotic Superconductors

TL;DR

This paper extends Landau's quasiparticle formalism to exotic superconductors, explaining anomalous properties and doping effects through interaction-induced flat bands, thus providing a unified theoretical framework.

Contribution

The authors generalize the quasiparticle formalism to exotic superconductors and explain doping-dependent properties via flat bands, advancing understanding beyond standard BCS theory.

Findings

Quasiparticle number remains equal to particle number in exotic superconductors.

Doping variations of superfluid density and resistivity coefficient are explained by flat bands.

The formalism unifies the description of conventional and exotic superconducting phenomena.

Abstract

The quasiparticle formalism invented by Lev Landau for description of conventional Fermi liquids is generalized to exotic superconductivity attributed to Cooper pairing, whose measured properties defy explanation within the standard BCS-Fermi Liquid description. We demonstrate that in such systems the quasiparticle number remains equal to particle number, just as in common Fermi liquids. We are then able to explain the puzzling relationship between the variation with doping $x$ of two key properties of the family La$_{2-x}$Sr$_x$Cu0$_4$ of exotic superconductors, namely the $T=0$ superfluid density $\rho_{s0}(x)$ and the coefficient $A_1(x)$ in the linear-in-$T$ component of the normal-state low-$T$ resistivity $\rho(T)=\rho_0+A_1T+A_2T^2$, in terms of the presence of interaction-induced flat bands in the ground states of these metals.