Combining the advantages of superconducting MgB2 and CaC6 in one material: Suggestions from first-principles calculations

Abstract

We show that a recently predicted layered phase of lithium monoboride Li2B2 combines the key mechanism for strong electron-phonon coupling in MgB2 (i.e., interaction of covalent Bσ bands with B bond-stretching modes) with the dominant coupling mechanism in CaC6 (i.e., interaction of free-electron-like interlayer states with soft intercalant modes). Yet, surprisingly, the electron-phonon coupling in Li2B2 is calculated to be weaker than in either MgB2 or CaC6. We demonstrate that this is due to the accidental absence of Bπ states at the Fermi level in Li2B2. In MgB2, the π electrons play an indirect but important role in strengthening the coupling of σ electrons. Doping Li2B2 to restore π electrons at the Fermi level is expected to lead to a new superconductor that could surpass MgB2 in Tc.

Source-reported materials — not catalogue approval

Similar papers