Sensitivity of $T_{\rm c}$ to pressure and magnetic field in the cuprate superconductor YBa$_{2}$Cu$_{3}$O$_{y}$: evidence of charge order suppression by pressure

TL;DR

This study demonstrates that applying pressure suppresses charge density-wave order in YBa₂Cu₃O₆₊y, affecting the superconducting transition temperature and revealing a smoother dome, highlighting the competition between charge order, pseudogap, and superconductivity.

Contribution

It provides direct evidence that pressure suppresses charge order in YBCO without affecting the pseudogap, and links this suppression to changes in the superconducting dome.

Findings

Pressure suppresses charge order in YBCO.

Superconducting transition temperature shifts similarly with pressure and magnetic field but in opposite directions.

The suppression of charge order removes the 1/8 anomaly, leading to a smooth T_c dome.

Abstract

Cuprate superconductors have a universal tendency to form charge density-wave (CDW) order which competes with superconductivity and is strongest at a doping $p \simeq 0.12$. Here we show that in the archetypal cuprate YBa$_{2}$Cu$_{3}$O$_{y}$ (YBCO) pressure suppresses charge order, but does not affect the pseudogap phase. This is based on transport measurements under pressure, which reveal that the onset of the pseudogap at $T^*$ is independent of pressure, while the negative Hall effect, a clear signature of CDW order in YBCO, is suppressed by pressure. We also find that pressure and magnetic field shift the superconducting transition temperature $T_{\rm c}$ of YBCO in the same way as a function of doping - but in opposite directions - and most effectively at $p \simeq 0.12$. This shows that the competition between superconductivity and CDW order can be tuned in two ways, either by suppressing superconductivity with field or suppressing CDW order by pressure. Based on existing high-pressure data and our own work, we observe that when CDW order is fully suppressed at high pressure, the so-called "1/8 anomaly" in the superconducting dome vanishes, revealing a smooth $T_{\rm c}$ dome which now peaks at $p \simeq 0.13$. We propose that this $T_{\rm c}$ dome is shaped by the competing effects of the pseudogap phase below its critical point $p^{\star} \sim 0.19$ and spin order at low doping.