paper

Full-gap superconductivity in non-centrosymmetric Re $_{6}$ Zr, Re $_{27}$ Zr $_{5}$ and Re $_{24}$ Zr $_{5}$

arXiv:1612.02520 · doi:10.1103/PhysRevB.94.214513

Abstract

Non-centrosymmetric superconductor Re $_{6}$ Zr has attracted much interest, for its possible unconventional superconducting state with time reversal symmetry broken. Here we report the $^{185/187}$ Re nuclear quadrupole resonance (NQR) measurements on Re $_{6}$ Zr ( $T_{c}$ = 6.72 K) and the isostructural compounds Re $_{27}$ Zr $_{5}$ ( $T_{c}$ = 6.53 K) and Re $_{24}$ Zr $_{5}$ ( $T_{c}$ = 5.00 K). The nuclear spin-lattice relaxation rate $1/ T_{1}$ shows a coherence peak below $T_{c}$ and decreases exponentially at low temperatures in all three samples. The superconducting gap $I^$ derived from the $1/ T_{1}$ data is $2 I^ = 3.58$ $k_{B} T_{c}$ , 3.55 $k_{B} T_{c}$ , and 3.51 $k_{B} T_{c}$ for Re $_{6}$ Zr ,Re $_{27}$ Zr $_{5}$ , and Re $_{24}$ Zr $_{5}$ , respectively, which is close to the value of 3.53 $k_{B} T_{c}$ expected for weak-coupling superconductivity. These data suggest conventional $s$ -wave superconductivity with a fully-opened gap in this series of compounds.

Phys. Rev. B (in press)

Full-gap superconductivity in non-centrosymmetric Re6​Zr, Re27​Zr5​ and Re24​Zr5​

Abstract

Full-gap superconductivity in non-centrosymmetric Re $_{6}$ Zr, Re $_{27}$ Zr $_{5}$ and Re $_{24}$ Zr $_{5}$