Observation of quasiparticles for phase incoherent d-wave pairing in Bi2212

TL;DR

This study provides evidence for phase-incoherent d-wave pairing above Tc in Bi2212, revealing that pair formation persists without phase coherence, characterized by momentum-independent parameters and a specific scattering rate condition.

Contribution

It demonstrates the existence of phase-incoherent d-wave pairing above Tc in Bi2212 through momentum-independent parameters and scattering rates, offering new insights into the pseudogap regime.

Findings

Evidence of a single-particle gap above Tc in Bi2212.

Pair formation persists without phase coherence above Tc.

Superconducting transition governed by scattering rate balance.

Abstract

In contrast to a complex feature of antinodal state, suffering from competing order(s), the "pure" pairing gap of cuprates is detected in the nodal region, which therefore holds the key to the superconducting mechanism. The pairing gap has been viewed to be rather conventional, closing at the superconducting transition temperature (Tc). However, the density of states contributed from the nodal region was claimed to have a gap-like structure even above Tc. Here we present a missing evidence for a single-particle gap near the node signifying the realization of a phase incoherent d-wave superconductivity above Tc in the optimally doped Bi2Sr2CaCu2O8+d. We find that the pair formation is formulated by momentum-independent temperature evolutions of three parameters: a BCS-type energy gap (Delta), a single particle scattering rate (Gamma_single) and a pair breaking rate (Gamma_pair). The superconductivity occurs when the Gamma_pair value is suppressed smaller than Gamma_single on cooling, and the magnitude of Tc in cuprates is governed by a condition of Gamma_single(Tc)=Gamma_pair(Tc).