On the superconductivity in the system with preformed pairs

TL;DR

This paper explores a superconductivity model based on preformed pairs coexisting with unpaired fermions, highlighting a mean-field-like transition and analyzing Hall effect behavior, with implications for underdoped cuprates.

Contribution

It introduces a phenomenological model of superconductivity involving preformed pairs and unpaired fermions, with detailed analysis of Hall effect in different regimes.

Findings

The transition is more mean field-like with a small Ginzburg parameter.

Hall effect in the vortex and fluctuation regimes varies significantly from traditional models.

The model fits underdoped YBaCuO data but not optimally doped or LaSrCuO materials.

Abstract

We discuss the phenomenology of the superconductivity resulting from the bose condensation of the preformed pairs coexisting with unpaired fermions. We show that this transition is more mean field like than usual bose condensation, i.e. it is characterized by a relatively small value of the Ginzburg parameter. We consider the Hall effect in the vortex flow regime and in the fluctuational regime above $T_c$ and show that in this situation it is much less than in the transition driven entirely by bose condesation but much larger than in a usual superconductivity. We analyse the available Hall data and conclude that this phenomenology describes reasonably well the data in the underdoped materials of $YBaCuO$ family but is not an appropriate description of optimally doped materials or underdoped $LaSrCuO$.