The noncentrosymmetric superconductor Re6Zr has attracted much interest for its possible unconventional superconducting state with broken time-reversal symmetry. Here we report Re185/187 nuclear quadrupole resonance measurements on Re6Zr (Tc=6.72 K) and the isostructural compounds Re27Zr5 (Tc=6.53 K) and Re24Zr5 (Tc=5.00 K). The nuclear spin-lattice relaxation rate 1/T1 shows a coherence peak below Tc and decreases exponentially at low temperatures in all three samples. The superconducting gap Δ derived from the 1/T1 data is 2Δ=3.58kBTc,3.55kBTc, and 3.51kBTc for Re6Zr,Re27Zr5, and Re24Zr5, respectively, which is close to the value of 3.53kBTc expected for weak-coupling superconductivity. These data suggest conventional s-wave superconductivity with a fully opened gap in this series of compounds.
ASJC Scopus subject areas
- Condensed Matter Physics