Metallochloronitrides: Electronic pairing mechanism in a new class of superconductors

A new class of doped layered superconductors has been discovered recently: the metallochloronitrides. Intercalating metallic atoms (Na, Li) into the layered parent compounds MNX (M = Zr, Hf and X = Cl, Br) superconductivity was found below a transition temperature that can be as high as Tc ∼ 26 K. We show that the dominant contribution to the pairing interaction is electronic and comes from the screened dynamical Coulomb interaction characteristic of layered systems. With use of parameters for Li0.48 (THF)y HfNCI we show that the calculated Tc is in quantitative agreement with experiment.