Anisotropic upper critical magnetic fields in Rb2Cr3As3 superconductor

Abstract

Rb2Cr3As3 is a structurally one-dimensional superconductor containing Cr3As3 chains with a superconducting transition temperature of K. Here we report the electrical resistance measurements for Rb2Cr3As3 single crystals, under magnetic fields up to 29.5 T and at temperatures down to 0.36 K, from which the upper critical fields, , can be obtained in a broad temperature range. For field parallel to the Cr3As3 chains, is paramagnetically limited with an initial slope of d/d T and a zero-temperature upper critical field of T. For field perpendicular to the Cr3As3 chains, however, is only limited by orbital pair-breaking effect with d/d T . As a consequence, the anisotropy decreases sharply near Tc and reverses below 2 K. Remarkably, the low-temperature down to 0.075 remains to increase linearly up to over three times the Pauli paramagnetic limit, which strongly suggests dominant spin-triplet superconductivity in Rb2Cr3As3.