D-wave Bose-Einstein condensation and the London penetration depth in superconducting cuprates

TL;DR

This paper proposes that bipolaron formation causes a d-wave Bose-Einstein condensate in cuprates, explaining the unusual temperature dependence of the magnetic field penetration depth through boson localization in a random potential.

Contribution

It introduces a bipolaron-based model for d-wave symmetry and explains penetration depth behavior without relying solely on pairing interactions.

Findings

Bipolaron formation leads to d-wave Bose-Einstein condensation in cuprates.

Localization of bosons explains the low-temperature penetration depth behavior.

Temperature dependence of penetration depth varies with random potential profile.

Abstract

We show that bipolaron formation leads to a d-wave Bose-Einstein condensate in cuprates. It is the bipolaron energy dispersion rather than a particular pairing interaction which is responsible for the d-wave symmetry. The unusual low-temperature dependence of the magnetic field penetration depth in cuprates is explained by the localisation of bosons in the random potential. The temperature dependence of the penetration depth is linear with positive or negative slope depending on the random field profile.