Abstract
Superconducting (SC) gap symmetry and magnetic response of cubic are studied by means of high-precision heat-capacity and dc magnetization measurements using a single crystal, in order to address the long-standing question of its second phase transition at in the SC state below . The absence (presence) of an anomaly at in the field-cooling (zero-field-cooling) magnetization indicates that this transition is between two different SC states. There is a qualitative difference in the field variation of the transition temperatures; is isotropic, whereas exhibits a weak anisotropy between the [001] and [111] directions. In the low-temperature phase below , the angle-resolved heat capacity reveals that the gap is fully opened over the Fermi surface, narrowing down the possible gap symmetry.
- Received 16 February 2017
- Revised 13 July 2017
DOI:https://doi.org/10.1103/PhysRevB.96.100505
©2017 American Physical Society