Strain-Switchable Field-Induced Superconductivity

The generation of new phases in quantum materials by external tuning parameters has become a central focus of condensed matter physics. Here, we demonstrate field-induced superconductivity at T = 10 K and B = 0.27 T which can be turned on and off by applying uniaxial stress. We use a sample of Eu(Fe_0.85Co_0.15)₂As₂ in which ferromagnetism and superconductivity coexist in a delicate balance. We combine tunable uniaxial stress and applied magnetic field to induce superconductivity above the zero-field transition temperature. We identify the Eu moment alignment as the mechanism of the field-induced superconductivity by using x-ray magnetic circular dichroism to monitor the field reorientation of Eu moments from out of plane to in-plane. Finally, we do a comprehensive x-ray diffraction characterization of the lattice response to stress and show how strain applied in the B1g symmetry channel can suppress nematic order which likely enhances superconductivity. This result presents this material as a platform for switchable field induced superconductivity.