Low-temperature magnetothermal transport investigation of a Ni-based superconductor BaNi2As2: Evidence for fully gapped superconductivity

We have performed low-temperature specific heat and thermal conductivity measurements of the Ni-based superconductor BaNi2As2 (Tc=0.7K) in a magnetic field. In a zero field, thermal conductivity shows T-linear behavior in the normal state and exhibits a BCS-like exponential decrease below Tc. The field dependence of the residual thermal conductivity extrapolated to zero temperature is indicative of a fully gapped superconductor. This conclusion is supported by the analysis of the specific heat data, which are well fit by the BCS temperature dependence from Tc down to the lowest temperature of 0.1 K.