Evidence for anisotropic superconductivity beyond Pauli limit in infinite-layer lanthanum nickelates.

After being expected as a promising analogue to cuprates for decades, superconductivity was recently 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, we show strong anisotropic magnetotransport behaviors in La-based nickelate films with enhanced crystallinity and superconductivity ( T c o n s e t $T_c^{onset}$ = 18.8 K, T c z e r o $T_c^{zero}$ = 16.5 K). The upper critical fields are anisotropic and violate the estimated BCS Pauli limit ( H P a u l i , μ = 1 μ B = 1.86 × T c , H = 0 ${H}_{Pauli,\mu \ = \ 1{\mu }_B} = \ 1.86 \times {T}_{c,H\ = \ 0}$ ) for in-plane magnetic fields. Moreover, the anisotropic superconductivity has been further manifested by the cusp-like peak of the angle-dependent T c and the vortex motion anisotropy under external magnetic fields. This article is protected by copyright. All rights reserved.