Electronic structure and weak electron-phonon coupling in TaB2 -: art. no. 144516

We present electronic structure calculations together with resistivity, susceptibility, and specific heat measurements for TaB2 to search for the recently contradictorily reported superconductivity and to Study related normal-state properties. We ascribe the absence of superconductivity down to 1.5 K for our TaB2 samples to the generally weak electron-phonon coupling derived from comparison of the calculated and measured specific heat constants. For the E-2g and the B-1g Gamma -point phonons, we derive from the calculated deformation potentials very small electron-phonon couplings for these modes, as opposed to the strong coupling of the E-2g mode in MgB2, probably responsible for its high T-c. In comparison to MgB2, we discuss the origin of the quite different features in the density of states and of the Fermi surfaces. The differences are mainly due to the strong hybridization between Ta 5d and B 2p states outside the hexagonal basis plane.