Spatially inhomogeneous competition between superconductivity and the charge density wave in YBa<sub>2</sub>Cu<sub>3</sub>O<sub>6.67</sub>.

Choi, J; Ivashko, O; Blackburn, E; Liang, R; Bonn, D A; Hardy, W N; Holmes, A T; Christensen, N B et al. · Nat Commun · 2020

basic_science · Level V

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Abstract

The charge density wave in the high-temperature superconductor YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7-x</sub> (YBCO) has two different ordering tendencies differentiated by their c-axis correlations. These correspond to ferro- (F-CDW) and antiferro- (AF-CDW) couplings between CDWs in neighbouring CuO<sub>2</sub> bilayers. This discovery has prompted several fundamental questions: how does superconductivity adjust to two competing orders and are either of these orders responsible for the electronic reconstruction? Here we use x-ray diffraction to study YBa<sub>2</sub>Cu<sub>3</sub>O<sub>6.67</sub> as a function of magnetic field and temperature. We show that regions with F-CDW correlations suppress superconductivity more strongly than those with AF-CDW correlations. This implies that an inhomogeneous superconducting state exists, in which some regions show a fragile form of superconductivity. By comparison of F-CDW and AF-CDW correlation lengths, it is concluded that F-CDW ordering is sufficiently long-range to modify the electronic structure. Our study thus suggests that F-CDW correlations impact both the superconducting and normal state properties of YBCO.