Pressure dependence of the oxygen isotope effect in YBa$_2$Cu$_4$O$_8$

TL;DR

This study investigates how applying pressure affects the oxygen isotope effect on the critical temperature in YBa2Cu4O8, revealing a consistent pressure dependence and insights into competing phenomena in high-temperature superconductivity.

Contribution

First measurement of pressure dependence of oxygen isotope effect on Tc in YBa2Cu4O8, providing new insights into the interplay of stripe order, pseudogap, and fluctuations.

Findings

Large pressure dependence of Tc for both isotopes

Isotope exponent remains low (~0.08) but increases slightly with pressure

Results discussed in context of stripe suppression and pseudogap effects

Abstract

We have carried out measurements of the pressure dependence to 1.2 GPa of the oxygen isotope effect on $T_c$ in the high-$T_c$ superconductor YBa$_2$Cu$_4$O$_8$ using a clamp cell in a SQUID magnetometer. This compound lies close to, but just above, the 1/8$^{th}$ doping point where in La$_{2-x}$Sr$_x$CuO$_4$ marked anomalies in isotope effects occur. Both isotopes show the same very large pressure dependence of $T_c$ with the result that the isotope exponent remains low ($\sim$0.08) but increases slightly with increasing pressure. This is discussed in terms of stripe suppression, a competing pseudogap and the effect of superconducting fluctuations.