Electronic structure of superconducting MgB2 and related binary and ternary borides

Abstract

First-principles full potential linear muffin-tin orbital–generalized gradient approximation electronic structure calculations of the new medium-TC superconductor (MTSC) MgB2 and related diborides indicate that superconductivity in these compounds is related to the existence of px,y-band holes at the Γ point. Based on these calculations, we explain the absence of medium-TC superconductivity for BeB2, AlB2, ScB2, and YB2. The simulation of a number of MgB2-based ternary systems using a supercell approach demonstrates that (i) the electron doping of MgB2 (i.e., MgB2−yXy with X=Be, C, N, O) and the creation of defects in the boron sublattice (nonstoichiometric MgB2−y) are not favorable for superconductivity, and (ii) a possible way of searching for similar or higher MTSC should be via hole doping of MgB2 (CaB2) or isoelectronic substitution of Mg (i.e., Mg1−xMxB2 with M=Be, Ca, Li, Na, Cu, Zn) or creating layered superstructures of the MgB2/CaB2 type.

Source-reported materials — not catalogue approval

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