Structure and Tc of Y0.8Ca0.2Ba2Cu3O6.92 under High Pressure

TL;DR

This study investigates how high pressure affects the lattice parameters and critical temperature (Tc) of Y0.8Ca0.2Ba2Cu3O6.92, revealing that an extended charge transfer model incorporating compressibility changes accurately predicts Tc variations.

Contribution

The paper refines the extended charge transfer model by linking it to pressure-induced compressibility changes, improving the prediction of Tc under high pressure.

Findings

Pressure influences Tc through charge transfer and lattice compressibility.

The modified model aligns well with experimental Tc(p) data.

Standard assumptions of constant dnh/dp and dTc,max/dp are inadequate.

Abstract

The lattice parameters and Tc of Y1-yCayBa2Cu3Ox have been determined under pressure up to 10 GPa using a diamond anvil cell. The results are used to test the extended charge transfer model that connects the pressure effect on Tc to an intrinsic dTc,max/dp and a pressure induced hole doping dnh/dp, the latter being caused by charge transfer from the CuO chains to the CuO2 planes. dnh/dp and dTc,max/dp are usually assumed to be constant with respect to pressure p. However, our experiments show that the usage of this model gives a poor description of the experimental Tc(p) values. We connected the extended charge transfer model to the pressure induced changes of the compressibilities. With this ansatz the calculated Tc(p) values show an excellent agreement with the experimentally determined values.