Superconductivity in infinite-layer nickelate La<sub>1-x</sub>Ca<sub>x</sub>NiO<sub>2</sub> thin films.

Zeng, Shengwei; Li, Changjian; Chow, Lin Er; Cao, Yu; Zhang, Zhaoting; Tang, Chi Sin; Yin, Xinmao; Lim, Zhi Shiuh et al. · Sci Adv · 2022

basic_science · Level V

Where this comes from

Abstract

We report the observation of superconductivity in infinite-layer Ca-doped LaNiO<sub>2</sub> (La<sub>1-<i>x</i></sub>Ca<i><sub>x</sub></i>NiO<sub>2</sub>) thin films and construct their phase diagram. Unlike the metal-insulator transition in Nd- and Pr-based nickelates, the undoped and underdoped La<sub>1-<i>x</i></sub>Ca<i><sub>x</sub></i>NiO<sub>2</sub> thin films are entirely insulating from 300 K down to 2 K. A superconducting dome is observed at 0.15 < <i>x</i> < 0.3 with weakly insulating behavior at the overdoped regime. Moreover, the sign of the Hall coefficient <i>R</i><sub>H</sub> changes at low temperature for samples with a higher doping level. However, distinct from the Nd- and Pr-based nickelates, the <i>R</i><sub>H</sub>-sign-change temperature remains at around 35 K as the doping increases, which begs further theoretical and experimental investigation to reveal the role of the 4f orbital to the (multi)band nature of the superconducting nickelates. Our results also emphasize a notable role of lattice correlation on the multiband structures of the infinite-layer nickelates.