The low-temperature specific heat of single-crystal samples of superconducting MgCNi_3 with typical dimensions 200 μm were measured for the first time. A computer controlled ac microcalorimeter using an optical fiber and an infrared light-emitting diode as the heat source was used down to 2 K at magnetic fields up to 8 T. The specific heat data suggest a moderate coupling in MgCNi_3.
The first point-contact spectroscopy measurements on MgCNi_3 single crystals of very good quality are presented. The measurements have been performed in the temperature range from 1.5 K up to 10 K and at magnetic fields up to 6 T. The superconducting energy gap Δ of the system is found to be scattered between 1 and 1.2 meV which gives the 2Δ/k T_c ratio between BCS weak-coupling value of ~3.5 and a strong coupling of about 4.2. The excess current evaluated in magnetic field indicates the presence of a single energy gap.
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.