Continuous Strain Tuning of Cuprate Superconductivity in Freestanding Membranes*

In recent years, strain engineering has proven to be a powerful tool for elucidating the complex interplays between structural, electronic, and spin degrees of freedom. In the field of high-T_c cuprate superconductivity research, it has been shown to tune effectively the superconducting phase and other competing orders [1]. However, the intrinsic brittleness of the cuprate oxides has mostly limited these previous works to studying the system’s response to compressive stress. Much of the strain dependence phase space remains unexplored on the tensile side. Utilizing a bespoke in situ manipulation stage, in combination with the development of freestanding La_2-xSr_xCuO₄ membranes, we study how the superconducting state and the normal state properties evolve against tensile strains of various symmetries and magnitude beyond 1%. We find signs of a novel intermediate phase where the superconducting phase coherence within the Cu-O plane can be sensitively tuned by tensile strain.

[1] J. Zhang et al., Nanomaterials 12, 3340 (2022).