Engineering Phase Competition Between Stripe Order and Superconductivity in La_1.88Sr_0.12CuO_4

Unconventional superconductivity often couples to other electronic orders in a cooperative or competing fashion. Identifying external stimuli that tune between these two limits is of fundamental interest. Here, we show that c-axis strain couples directly to the competing interaction between charge stripe order and superconductivity in La_1.88Sr_0.12CuO_4 (LSCO). Compressive c-axis pressure amplifies stripe order within the superconducting state, while having no impact on the normal state. By contrast, strain dramatically diminishes the magnetic field enhancement of stripe order in the superconducting state. This observation hints to the existence of a ground state without phase competition. As such, c-axis pressure is a promising tuning parameter in the search for ground states where superconductivity adopts broken translational symmetry from charge ordering phenomena.