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

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 ( T c onset Tc^onset = 18.8 K, T c zero Tc^zero = 16.5 K). The upper critical fields are anisotropic and violate the estimated Bardeen-Cooper-Schrieffer (BCS) Pauli limit ( H Pauli , μ = 1 μ B = 1.86 × T c , H = 0 H_Pauli,μ =1μB=1.86×Tc,H=0 ) for in-plane magnetic fields. Moreover, the anisotropic superconductivity is further manifested by the cusp-like peak of the angle-dependent Tc and the vortex motion anisotropy under external magnetic fields.