The cuprate superconductor La$_{ 2-x}$Ba$_x$CuO$_4$ (LBCO) near $x=0.125$ is a striking example of intertwined electronic orders, where 3D superconductivity is anomalously suppressed, allowing spin and charge stripe order to develop, in a manner consistent with the emergence of a pair-density-wave (PDW) state. Understanding this interplay remains a key challenge in cuprates, highlighting the necessity of external tuning for deeper insight. While in-plane (within the CuO plane) uniaxial stress enhances superconductivity and suppresses stripe order, the effects of $c$-axis compression (perpendicular to the CuO plane) remains largely unexplored. Here, we use muon spin rotation ($\mu$SR) and AC susceptibility with an in situ piezoelectric stress device to investigate the spin-stripe order and superconductivity in LBCO-0.115 under $c$-axis compression. The measurements reveal a gradual suppression of the superconducting transition temperature ($T_{ \rm c}$) with increasing $c$-axis stress, in stark contrast to the strong enhancement observed under in-plane stress. We further show that while in-plane stress rapidly reduces both the magnetic volume fraction ($V_{ \rm m}$) and the spin-stripe ordering temperature ($T_{ \rm so}$), $c$-axis compression has no effect, with $V_{ \rm m}$ and $T_{ \rm so}$ exhibiting an almost unchanged behavior up to the highest applied stress of 0.21 GPa. These findings demonstrate a strong anisotropy in stress response, underscoring the critical role of crystallographic anisotropy in governing competing electronic phases in LBCO.
Categories: cond-mat.supr-con cond-mat.mtrl-sci cond-mat.str-el
