Electron doping in the honeycomb bilayer superconductors (Zr, Hf)NCl

PACS. 74.25Kc – Phonons. Abstract. – Based on a virtual crystal treatment, we show that alkali doping introduces electron carriers into a single light mass (m ∗ = 0.6), low density of states band in LixZrNCl and NaxHfNCl (which have superconducting Tc up to 25 K) that is a symmetric interlayer combination of dxy, dx2−y2 character. Doping leads to simple K-centered three-fold symmet-rical cylindrical Fermi surfaces that concentrate low-energy scattering into distinct regions of momentum. The lack of any observed magnetic tendencies, together with our calculation of small electron-phonon strength, suggests a pairing mechanism that is distinct from known superconductors. Superconductivity in doped quasi–two-dimensional (2D) compounds has been of intense interest since the discovery of the strong dependence of the critical temperature, Tc, on intercalation of the transition metal dichalcogenides [1], and the discovery of high Tc in 2D cuprates further heightened their study. The manner in which doping of 2D layers alters their electronic behaviour varies greatly depending on the system. Cuprate high-temperature superconductors, for instance, have a magnetic insulator to metal transition that completel