Synthesis and search for superconductivity in LiBC

Abstract

Following the recent theoretical prediction of superconductivity in hole doped LiBC by Rosner et al. [Phys. Rev. Lett. 88 (2002) 127001], we have attempted to synthesise Li deficient Li_xBC (x=1, 0.8, 0.6 and 0.4) and look for superconductivity in this system. Our synthesis procedure, following the recipe for MgB₂, involves reaction of elemental components in a Ta crucible at 900 ° C under 50 bar of Argon pressure. X-ray diffraction measurements indicate the formation of P6₃/mmc structure up to x=0.6. However, no diamagnetic signal or zero resistance, corresponding to the superconducting transition, was observed in the temperature range of 300 to 4K. This is possibly related to the presence of disorder in the B-C stacking; evidence for which is suggested from a study of the vibrational modes of Li_xBC through infrared spectroscopy.