The Effects of Chemical Doping and Hydrostatic Pressure on Tc of Y(1-y)CayBa2Cu3Ox and NdBa2Cu3Ox Single Crystals

TL;DR

This study investigates how chemical doping and hydrostatic pressure affect the critical temperature (Tc) of various YBa2Cu3Ox and NdBa2Cu3Ox single crystals, revealing the influence of structural changes and hole concentration on superconductivity.

Contribution

It provides new insights into how doping and pressure alter Tc through changes in hole concentration and lattice structure in high-temperature superconductors.

Findings

Doping shifts Tc(x) curves and alters maximum Tc.

Pressure effects on Tc vary with doping level and structural order.

Lattice deformations significantly influence electronic structure and Tc.

Abstract

We studied Tc of YBa2Cu3Ox (Y123), Y0.89Ca0.11Ba2Cu3Ox (YCa123) and NdBa2Cu3Ox (Nd123) single crystals with various oxygen contents x. Compared to Tc(x) of Y123 the Tc(x) curves of YCa123 are shifted to lower oxygen contents and the maximum transition temperature Tc,max decreases with increasing Ca content whereas in Nd123 Tc(x) is shifted to higher oxygen contents and Tc,max is increased. According to the universal parabolic Tc(nh) behavior the differences in Tc(x)of Y123, YCa123 and Nd123 can be ascribed to different hole concentrations nh in the CuO2 planes caused by doping via changes in chemistry or structure. In order to study the influence of structural changes on Tc we examined the hydrostatic pressure effect dTc/dp (p up to 0.6 GPa). In the underdoped region, at nh=0.11, the examined compounds show a peak in dTc/dp which is very pronounced for systems with well ordered CuO chains. As this peak occurs at the same nh in all investigated systems it is not caused by oxygen ordering, but its origins might be found in a strong influence of lattice deformations on the electronic structure.