Magnetic penetration depth and T_{c} in superconducting nickelates

Abstract

We compute the nominal magnetic penetration depth of RNiO_{2} (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 ∼180 K according to the Nelson-Kosterliz universal relation between the superfluid density and the transition temperature.