Uniaxial Pressure Control of Competing Orders in a High Temperature Superconductor

External control of electronic phases in correlated-electron materials is a long-standing challenge of condensed-matter research. Layered cuprates exhibit antiferromagnetic, charge density-wave (CDW), and high-temperature superconducting ground states which can be tuned by doping and external magnetic fields. However, disorder generated by lattice defects and randomly pinned magnetic vortices greatly complicates the interpretation of these experiments.

Here, we report a high-resolution inelastic x-ray scattering study of the high-temperature superconductor YBa2Cu3O6.67 under uniaxial stress (1), and show that a three-dimensional long range-ordered CDW state can be induced by pressure along the a-axis, in the absence of magnetic fields. The amplitude of the CDW is strongly suppressed below the superconducting transition temperature, indicating strong thermodynamic competition with superconductivity. We also show that the transition is driven by the complete softening of an optical phonon mode.

The results provide new insights into the anomalous normal-state properties of high temperature superconductors and illustrate the potential of uniaxial-pressure control of competing orders in quantum materials.

(1) Kim et al. Science 362, 1040 (2018))