The Effect of Chemical Doping and Hydrostatic Pressure on Tc of Y1-yCayBa2Cu3Ox Single Crystals

TL;DR

This study investigates how chemical doping with calcium and the application of hydrostatic pressure affect the critical temperature (Tc) of Y1-yCayBa2Cu3Ox single crystals, revealing doping-dependent pressure effects and disorder influences.

Contribution

It provides a detailed analysis of pressure-induced charge transfer and disorder effects on Tc across different doping levels in Ca-doped cuprate crystals.

Findings

Pressure induces charge transfer with a consistent rate across Ca contents.

Peak dTc/dp occurs at ~0.11 holes/CuO2, depressed by Ca doping.

Disorder in CuO chains affects Tc behavior at low doping.

Abstract

We performed susceptibility measurements on Y1-yCayBa2Cu3Ox single crystals under high He pressure. For each Ca content various samples with different oxygen contents have been prepared to probe the influence of Ca on Tc(x), dTc/dp(x) and Tc,max. Starting from the parabolic Tc(nh) behavior we calculated nh values from Tc and Tc,max for each sample. It is shown that in the overdoped region dTc/dp can be described by a pressure induced charge transfer with dnh/dp = 3.7E-3 [1/GPa] and a dTc,max/dp value of 0.8 K/GPa, irrespective of the Ca content. In the underdoped region additional pressure effects lead to a peak in dTc/dp at approximately 0.11 holes/CuO2 plane. However, with increasing Ca content this peak is strongly depressed. This is explained in terms of an increasing disorder in the CuO chain system due to doping. Deviations in dTc/dp at very low nh values can be assigned to the ortho II ordering in the CuO chain system.