The Doping Phase Diagram of Y1-xcaxba2(Cu1-yzny)3O7-d from Transport Measurements: Tracking the Pseudogap Below Tc (y = 0)

TL;DR

This study investigates the pseudogap behavior in Y1-xCaxBa2(Cu1-yZny)3O7-d superconductors by analyzing resistivity data across various doping levels, revealing that the pseudogap persists below Tc and depends solely on hole concentration.

Contribution

The paper provides detailed transport measurements showing the pseudogap's persistence below Tc and its independence from disorder, refining understanding of the phase diagram in cuprate superconductors.

Findings

Pseudogap temperature T* depends only on hole concentration p.

T* persists below Tco on the overdoped side and does not merge with Tco.

T* extrapolates to zero at p = 0.19 +/- 0.01.

Abstract

The effects of planar hole concentration, p, on the resistivity, r(T), of sintered Y1-xCaxBa2(Cu1-yZny)3O7-d samples were investigated over a wide range of Ca, Zn, and oxygen contents. Zn was used to suppress superconductivity and this enabled us to extract the characteristic pseudogap temperature, T*(p), from r(T,p) data below Tco(p) [ = Tc (y = 0)]. We have also located the characteristic temperature, Tscf, marking the onset of significant superconducting fluctuations above Tc, from the analysis of r(T,H,p) and r(T,p) data. This enabled us to identify T*(p) near the optimum doping level where the values of T*(p) and Tscf(p) are very close and hard to distinguish. We again found that T*(p) depends only on the hole concentration p, and not on the level of disorder associated with Zn or Ca substitutions. We conclude that (i) T*(p) (and therefore, the pseudogap) persists below Tco(p) on the overdoped side and does not merge with the Tco(p) line and (ii) T*(p), and thus the pseudogap energy, extrapolates to zero at the doping p = 0.19 +/- 0.01. PACS numbers: 74.25.Dw, 74.25. 74.62.Dh, 74.72.-h Key words: Pseudoap, Superconducting fluctuations