Emergence of Cooper pairs, d-wave duality and the phase diagram of cuprate superconductors

TL;DR

This paper explores the complex behavior of Cooper pairs in cuprate superconductors, revealing how doping influences their state, leading to pseudogaps and a transition from superconducting to antiferromagnetic correlations.

Contribution

It introduces a theory describing the varied fate of Cooper pairs in cuprates, explaining pseudogap phenomena and phase diagram features beyond traditional BCS and helium models.

Findings

At low doping, enhanced diamagnetism and short-range superconductivity emerge.

Two pseudogaps form as Cooper pairs disintegrate with underdoping.

Ground states shift from superconducting to antiferromagnetic correlations.

Abstract

BCS theory describes the formation of Cooper pairs and their instant "Bose condensation" into a superconducting state. Helium atoms are preformed bosons and, in addition to their condensed superfluid state, can also form a quantum solid, lacking phase-coherence. Here we show that the fate of Cooper pairs can be more varied than the BCS or helium paradigms. In copper-oxide d-wave superconductors (dSC) Cooper pairs are intrinsically non-local objects, with both center-of-mass and relative motions. As doping decreases, the center-of mass fluctuations force a correlated dSC into a state with enhanced diamagnetism and robust but short-ranged superconducting order. At extreme underdoping, the relative fluctuations take over and two pseudogaps -- ``small'' (charge) and ``large'' (spin) -- emerge naturally from the theory, as Cooper pairs ``disintegrate'' and charge ``detaches'' from spin-singlet bonds. The ensuing ground state(s) are governed by diagonal (mostly antiferromagnetic) rather than by superconducting (off-diagonal) correlations. The theory is used to account for several recent experiments and to draw general conclusions about the phase diagram.