Dependence of T-c of YBa2Cu3O6.67 on in-plane uniaxial stress

We probe the effect on T-c of in-plane uniaxial stress applied to the high-temperature superconductor YBa2Cu3O6.67. We find a highly anisotropic response. Under compression along the b axis, which reduces the orthorhombicity of the CuO2 planes, T-c is broadly flat for stresses up to at least 1.7 GPa. Under compression along the a axis, T-c decreases steeply. For stresses beyond approximate to 1 GPa the decrease is quasilinear. We hypothesize that superconductivity is suppressed by competition with uniaxial charge density wave order, which has been found to onset at approximate to 1 GPa.