Bosonic versus fermionic pairs of topological spin defects in monolayered high-T_c superconductors

TL;DR

This paper compares bosonic and fermionic topological spin defect pairs in high-T_c superconductors, finding a doping level where bosonic pairs become energetically favorable, potentially explaining the onset of superconductivity.

Contribution

It introduces a detailed energy estimation of topological spin defect pairs using a resonating valence bond model, highlighting the conditions favoring bosonic pairs in high-T_c materials.

Findings

Bosonic pairs become energetically favorable at a critical doping level.

Both pairs exhibit x^2-y^2 symmetry in relevant parameters.

The energy crossover may relate to the onset of high-T_c superconductivity.

Abstract

The energy associated with bosonic and fermionic pairs of topological spin defects in doped antiferromagnetic quantum spin-1/2 square lattice is estimated within a resonating valence bond scenario, as described by a t-t'-J-like model Hamiltonian, plus a t-perpendicular, responsible of a three-dimensional screening of the electrostatic repulsion within the bosonic pairs. For parameters appropriate for monolayered high-T_c superconductors, both fermionic and bosonic pairs show x^2-y^2 symmetry. We find a critical value of doping such that the energy of the bosonic pairs goes below twice the energy of two fermionic pairs at their Fermi level. This finding could be related to the onset of high-T_c superconductivity.