First-Principles Investigation of Superconductivity in Transition Metal Carbides

ORAL

Abstract

We investigate the origin of superconductivity in the transition metal carbides TaC and HfC by a first-principles approach. The electronic structure is described within density functional theory in the local density approximation, and the lattice dynamical properties are determined through density functional perturbation theory. We calculate the average electron-phonon coupling strength through the isotropic approximation to the Migdal-Eliashberg theory, and the superconducting transition temperature through the McMillan formula. The calculated transition temperatures are found to be in excellent agreement with experiment. The relatively high transition temperature of TaC (10.3 K) is associated with a Kohn anomaly in the phonon dispersions, and arises from significant Fermi surface nesting. In contrast, the absence of nesting in HfC results in a limited phase-space availability for electron-phonon scattering. Correspondingly, HfC exhibits a negligible transition temperature ($<0.1$ K).

–

Authors

  • Jesse Noffsinger

    UC Berkeley, Lawrence Berkeley National Laboratory

  • Feliciano Giustino

    UC Berkeley, Lawrence Berkeley National Laboratory, University of California at Berkeley and Lawrence Berkeley National Laboratory

  • Steven Louie

    Molecular Foundry, Lawrence Berkeley National Laboratory and Department of Physics, University of California at Berkeley, Dept of Physics UC Berkeley, The Molecular Foundry LBNL, Mat Sci Div LBNL, Department of Physics, University of California at Berkeley and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, UC Berkeley, Lawrence Berkeley National Laboratory, University of California at Berkeley and Lawrence Berkeley National Laboratory, University of California at Berkeley, University of California, Berkeley \& Lawrence Berkeley National Laboratory, University of California at Berkeley and Lawrence Berkeley National Lab, Department of Physics, University of California, Berkeley, and Materials Sciences Division, Lawrence Berkeley National Laboratory

  • Marvin Cohen

    Dept of Physics UC Berkeley, Mat Sci Div LBNL, Department of Physics, University of California at Berkeley and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, UC Berkeley, Lawrence Berkeley National Laboratory, University of California at Berkeley and Lawrence Berkeley National Laboratory, UC Berkeley \& LBNL, UC Berkeley and Lawrence Berkeley National Laboratory