Abstract
Following the discovery of superconductivity in quasi-one-dimensional containing chains (J. K. Bao et al., arXiv:1412.0067), we succeeded in synthesizing an analogous compound, , which also crystallizes in a hexagonal lattice. The replacement of K by Rb results in an expansion of the axis by 3%, indicating a weaker interchain coupling in . Bulk superconductivity emerges at 4.8 K, above which the normal-state resistivity shows a linear temperature dependence up to 35 K. The estimated upper critical field at zero temperature exceeds the Pauli paramagnetic limit by a factor of 2. Furthermore, the electronic specific-heat coefficient extrapolated to zero temperature in the mixed state increases with , suggesting the existence of nodes in the superconducting energy gap. Hence manifests itself as another example of an unconventional superconductor in the -chain based system.
- Received 8 December 2014
- Revised 20 January 2015
DOI:https://doi.org/10.1103/PhysRevB.91.020506
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