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TT: Tiefe Temperaturen
TT 9: Neue und unkonventionelle Supraleiter I
TT 9.3: Talk
Tuesday, March 12, 2002, 10:00–10:15, H19
Prediction of High Tc Superconductivity in Hole-doped LiBC — •Helge Rosner, Alex Kitaigorodsky, and Warren E. Pickett — University of California, Davis, CA, 95616, USA
The layered lithium borocarbide LiBC, isovalent with and structurally similar to the superconductor MgB2, is an insulator due to the modulation within the hexagonal layers (BC vs. B2). Using LDA band structure calculations for super-cells and in virtual crystal approximation, we show that hole-doping of LiBC results in Fermi surfaces of B-C pσ character that couple very strongly to B-C bond stretching modes. These are precisely the features that lead to superconductivity at Tc ≃ 40 K in MgB2. Comparison of Li0.5BC with MgB2 indicates the former to be a prime candidate for electron-phonon coupled superconductivity at substantially higher temperature than in MgB2. At this doping level, the densities of states and the phonon frequencies of both compounds are comparable, whereas the deformation potential is 40% larger in Li0.5BC, resulting in an about twice as large electron phonon coupling λ in the latter. Due to its layered structure, LiBC seems to be a prime candidate for field-effect doping, offering a wide field of basic research for the whole compound family, and the possibility of technical applications.