The temperature dependence of the upper critical field (Hc2) in RbCrAs3 single crystals (Tc≈ 7.3 K) has been determined by means of magnetoresistance measurements with temperature down to 0.35 K in static magnetic fields up to 38 T. The magnetic field was applied both for directions parallel (H∥c, Hc2∥c) and perpendicular (H⊥c, Hc2⊥c) to the Cr chains. The curves Hc2∥c(T) and Hc2⊥c(T) cross at ∼ 5.5 K. As a result, the anisotropy parameter γ(T)=Hc2⊥c/Hc2∥c(T) increases from 0.5 near Tc to 1.6 at low temperature. Fitting with the Werthamer-Helfand-Hohenberg (WHH) model yields zero-temperature critical fields of μ0Hc2∥c(0)≈ 27.2 T and μ0Hc2⊥c(0)≈ 43.4 T, both exceeding the BCS weak-coupling Pauli limit μ0Hp=1.84Tc=13.4 T. The results indicate that the paramagnetic pair breaking effect is strong for H∥c but absent for H⊥c, which was further confirmed by the angle dependent magnetoresistance and Hc2 measurements.
@article{arxiv.1912.03806,
title = {The upper critical field and its anisotropy in RbCr$_{3}$As$_{3}$},
author = {Qimei Liang and Tong Liu and Chuanying Xi and Yuyan Han and Gang Mu and Li Pi and Zhi-An Ren and Zhaosheng Wang},
journal= {arXiv preprint arXiv:1912.03806},
year = {2019}
}