Electronic structure of superconducting MgB2 and related binary and ternary borides

N. I. Medvedeva; A. L. Ivanovskii; J. E. Medvedeva; A. J. Freeman

doi:10.1103/PhysRevB.64.020502

paper

Electronic structure of superconducting MgB2 and related binary and ternary borides

arXiv:cond-mat/0103157 · doi:10.1103/PhysRevB.64.020502

Abstract

First principles FLMTO-GGA electronic structure calculations of the new medium- $T_{C}$ superconductor (MTSC) $M g B_{2}$ and related diborides indicate that superconductivity in these compounds is related to the the existence of $p_{x, y}$ -band holes at the $Γ$ point. Based on these calculations, we explain the absence of medium- $T_{C}$ superconductivity for $B e B_{2}$ , $A l B_{2}$ $S c B_{2}$ and $Y B_{2}$ . The simulation of a number of $M g B_{2}$ -based ternary systems using a supercell approach demonstrates that (i) the electron doping of $M g B_{2}$ (i.e., $M g B_{2 - y} X_{y}$ with X=Be, C, N, O) and the creation of isoelectronic defects in the boron sublattice (nonstoichiometric $M g B_{y < 2}$ ) are not favorable for superconductivity, and (ii) a possible way of searching for similar MTSC should be via hole doping of $M g B_{2}$ (i.e., $M g_{1 - x} M_{x} B_{2}$ with M=Be, Ca, Li, Na, Cu, Zn) or $C a B_{2}$ or via creating layered superstructures of the $M g B_{2} / C a B_{2}$ type. A recent report of superconductivity in Cu doped $M g B_{2}$ supports this view.

12 pages, 4 figures

Electronic structure of superconducting MgB2 and related binary and ternary borides

Abstract

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