Anomalous pseudogap and superconducting state properties of heavily disordered Y1-xCaxBa2(Cu1-yZny)3O7-delta

TL;DR

This study investigates how heavy in-plane disorder from zinc affects the pseudogap and superconducting properties in Y1-xCaxBa2(Cu1-yZny)3O7-delta, revealing anomalous pseudogap behavior and suppressed superfluid density.

Contribution

It uncovers an unusual p-independence of the pseudogap temperature at high Zn levels and discusses the impact of disorder on vortex pinning and superconductivity.

Findings

Pseudogap temperature becomes p-independent at high Zn content.

Superfluid density is extremely low in heavily disordered samples.

High Zn concentration leads to anomalous pseudogap behavior.

Abstract

The role of substantial in-plane disorder (Zn) on the transport and AC susceptibility of Y1-xCaxBa2(Cu1-yZny)3O7-delta was investigated over a wide range of planar hole concentration, p. Resistivity, r(T), for a number of overdoped to underdoped samples with y equals/greater than 0.055 showed clear downturns at a characteristic temperature similar to that found at T* in Zn-free underdoped samples because of the presence of the pseudogap. Contrary to the widely observed behavior for underdoped cuprates at lower Zn contents (where the pseudogap energy increases almost linearly with decreasing p in the same way as for the Zn-free compounds), this apparent pseudogap temperature at high Zn content showed very little or no p-dependence. It also increases systematically with increasing Zn concentration in the CuO2 planes. This anomalous behavior appears quite abruptly, e.g., samples with y less than/equals 0.05 exhibit the usual T*(p) behavior. AC susceptibility of these heavily disordered samples showed the superfluid density to be extremely low. Magneto-transport, r(T,H), measurements are provisionally interpreted in terms of high-strength pinning centers for vortices in these samples. We also discuss various possible scenarios that might lead to a Zn induced pseudogap in the cuprates.