Unconventional superconductivity in quasi-one-dimensionalRb2Cr3As3

Following the discovery of superconductivity in quasi-one-dimensional\nK$_2$Cr$_3$As$_3$ containing [(Cr$_3$As$_3$)$^{2-}$]$_{\\infty}$ chains [J. K.\nBao et al., arXiv: 1412.0067 (2014)], we succeeded in synthesizing an analogous\ncompound, Rb$_2$Cr$_3$As$_3$, which also crystallizes in a hexagonal lattice.\nThe replacement of K by Rb results in an expansion of $a$ axis by 3\\%,\nindicating a weaker interchain coupling in Rb$_2$Cr$_3$As$_3$. Bulk\nsuperconductivity emerges at 4.8 K, above which the normal-state resistivity\nshows a linear temperature dependence up to 35 K. The estimated upper critical\nfield at zero temperature exceeds the Pauli paramagnetic limit by a factor of\ntwo. Furthermore, the electronic specific-heat coefficient extrapolated to zero\ntemperature in the mixed state increases with $\\sqrt{H}$, suggesting existence\nof nodes in the superconducting energy gap. Hence Rb$_2$Cr$_3$As$_3$ manifests\nitself as another example of unconventional superconductor in the\nCr$_3$As$_3$-chain based system.\n