Tuning of charge order by uniaxial stress in a cuprate superconductor

Strongly correlated electron materials are often characterized by competition and interplay of multiple quantum states. For example, in high-temperature cuprate superconductors unconventional superconductivity, spin- and charge-density wave orders coexist. A key question is whether competing states coexist on the atomic scale or if they segregate into distinct regions. Using X-ray diffraction, we investigate the competition between charge order and superconductivity in the archetypal cuprate La 2− x Ba x CuO 4 , around x = 1/8-doping, where uniaxial stress restores optimal 3D superconductivity at σ 3D ≈ 0.06 GPa. We find that the charge order peaks and the correlation length along the stripe are strongly reduced up to σ 3D . Upon the increase of stress beyond this point, no further changes were observed. Simultaneously, the charge order onset temperature only shows a modest decrease. Our findings suggest that optimal 3D superconductivity is not linked to the absence of charge stripes but instead requires their arrangement into smaller regions. Our results provide insight into the length scales over which the interplay between superconductivity and charge order takes place. In many quantum materials, different electronic phases can coexist or compete with one another. In this work uniaxial pressure is used to achieve the spatial distribution of charge order that maximizes the superconducting transition temperature.