Evidence for nodal superconductivity in infinite-layer nickelates from penetration depth measurements

Since their discovery in 2019, the infinite-layer nickelates, (A,Sr)NiO₂ (A=La, Pr, Nd) have been the subject of robust experimental and theoretical investigation. Determining the pairing symmetry of superconductivity is an important task that will guide theoretical investigations of the pairing mechanism in these materials. Measurements of the London penetration depth can indicate whether the superconducting gap is nodal or not, providing evidence for the pairing symmetry in the material. In this talk, I will present our measurements of the penetration depth for the infinite-layer nickelates across the A-site variants. We use a two-coil mutual inductance technique to measure the penetration depth as a function of magnetic field and temperature, and our results indicate that the infinite-layer nickelates have nodes in their superconducting gap and suggest that they are dirty d-wave superconductors. I will also present results on how their superfluid density changes as a function of chemical doping.