Electron density of states in the borocarbide intermetallic superconductors.

摘要: We present heat-capacity measurements in a magnetic field up to 7.7 T on the recently discovered borocarbide intermetallic superconductors ${\mathrm{LuNi}}_{2}$${\mathrm{B}}_{2}$C and ${\mathrm{LaPt}}_{1.7}$${\mathrm{Au}}_{0.3}$${\mathrm{B}}_{2}$C. For with ${\mathit{T}}_{\mathit{c}}$=16.5 K, we find large density of states at Fermi level, \ensuremath{\gamma}\ensuremath{\sim}19(2) mJ/mole ${\mathrm{K}}^{2}$, an effective Debye temperature ${\mathrm{\ensuremath{\Theta}}}_{\mathit{D}}$ 345 K. In comparison, ${\mathrm{LaPt}}_{1.7}$${\mathrm{Au}}_{0.3}$${\mathrm{B}}_{2}$C, ${\mathit{T}}_{\mathit{c}}$=10.2 has \ensuremath{\gamma} 7.5(1.5) ${\mathrm{K}}^{2}$ smaller 220 Through comparison specific-heat anomaly ${\mathit{T}}_{\mathit{c}}$, \ensuremath{\Delta}C/\ensuremath{\gamma}${\mathit{T}}_{\mathit{c}}$, susceptibility, calculated band structure, these compounds are found be weak-to-intermediate coupling limit \ensuremath{\lambda}\ensuremath{\approxeq}0.5--1.0. Their position \ensuremath{\gamma}-${\mathit{T}}_{\mathit{c}}$ plot indicates dominant phonon-mediated electron pairing.