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

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 Tc and the vortex motion anisotropy under external magnetic fields.

The Quest for High-Temperature Superconductivity in Nickelates under Ambient Pressure

“…With the focused effort of several groups, this result was improved further by optimizing the synthesis conditions [ 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. In La 0.8 Sr 0.2 NiO 2 , the best result reported was T c onset = 18.8 K and T c ( R = 0) = 16.5 K [ 13 ]. In 2022, the group at Harvard led by Julia Mundy reported superconductivity in Nd 6 Ni 5 O 12 with T c onset ≈ 13 K [ 14 ].…”