Magnetic penetration depth and T-c in superconducting nickelates

We compute the nominal magnetic penetration depth of RNiO2 (R = La, Nd) from first-principles calculations and discuss the results in relation to the superconducting T-c. We find a marked discrepancy with the well-established phenomenology that correlates these two quantities in cuprates (Uemura plot). We also consider the two-dimensional ultrathin limit and estimate the maximum attainable T-c to be similar to 180 K according to the Nelson-Kosterliz universal relation between the superfluid density and the transition temperature.