Direct observation of competition between superconductivity and charge density wave order in YBa2Cu3Oy

TL;DR

This study reveals that in YBa2Cu3Oy, charge density waves and superconductivity compete, with magnetic fields suppressing superconductivity and enhancing CDW, indicating a complex interplay influencing high-Tc superconductivity.

Contribution

The paper provides direct experimental evidence of competition between CDW and superconductivity in YBa2Cu3Oy using high-energy x-ray diffraction.

Findings

CDW develops in the normal state of YBa2Cu3Oy.

Magnetic field suppresses superconductivity and enhances CDW.

Results explain Fermi surface pockets and Hall effect observations.

Abstract

Superconductivity often emerges in the proximity of, or in competition with, symmetry breaking ground states such as antiferromagnetism or charge density waves (CDW)1-5. A number of materials in the cuprate family, which includes the high-transition-temperature (high-Tc) superconductors, show spin and charge density wave order5-7. Thus a fundamental question is to what extent these ordered states exist for compositions close to optimal for superconductivity. Here we use high-energy x-ray diffraction to show that a CDW develops at zero field in the normal state of superconducting YBa2Cu3O6.67 (Tc = 67 K). Below Tc, the application of a magnetic field suppresses superconductivity and enhances the CDW. Hence, the CDW and superconductivity are competing orders in this typical high-Tc superconductor, and high-Tc superconductivity can form from a pre-existing CDW state. Our results explain observations of small Fermi surface pockets8, negative Hall and Seebeck effect9,10 and the "Tc plateau"11 in this material when underdoped.