Evidence for Anisotropic Superconductivity Beyond Pauli Limit in Infinite‐Layer Lanthanum Nickelates

Abstract

Abstract After being expected to be a promising analog to cuprates for decades, superconductivity has recently been discovered in infinite‐layer nickelates, providing new opportunities to explore mechanisms of high‐temperature superconductivity. However, in sharp contrast to the single‐band and anisotropic superconductivity in cuprates, nickelates exhibit a multi‐band electronic structure and an unexpected isotropic superconductivity as reported recently, which challenges the cuprate‐like picture in nickelates. Here, it is shown that strong anisotropic magnetotransport behaviors exist in La‐based nickelate films with enhanced crystallinity and superconductivity ( = 18.8 K, = 16.5 K). The upper critical fields are anisotropic and violate the estimated Bardeen–Cooper–Schrieffer (BCS) Pauli limit () for in‐plane magnetic fields. Moreover, the anisotropic superconductivity is further manifested by the cusp‐like peak of the angle‐dependent T c and the vortex motion anisotropy under external magnetic fields.