Rotational symmetry breaking in superconducting nickelate Nd0.8Sr0.2NiO2 films

TL;DR

This study investigates the rotational symmetry breaking in Nd0.8Sr0.2NiO2 superconducting films, revealing a phase transition from isotropic to anisotropic states and uncovering an exotic electronic phase related to symmetry changes.

Contribution

It provides the first detailed analysis of symmetry breaking and phase transitions in nickelate superconductors using angular-dependent transport measurements.

Findings

Symmetry breaking from isotropic to four-fold anisotropy with increasing magnetic field.

Emergence of a two-fold symmetric component at low temperatures and high fields.

Observation of an anomalous upturn in the critical magnetic field.

Abstract

The infinite-layer nickelates, isostructural to the high-Tc superconductor cuprates, have risen as a promising platform to host unconventional superconductivity and stimulated growing interests in the condensed matter community. Despite numerous researches, the superconducting pairing symmetry of the nickelate superconductors, the fundamental characteristic of a superconducting state, is still under debate. Moreover, the strong electronic correlation in the nickelates may give rise to a rich phase diagram, where the underlying interplay between the superconductivity and other emerging quantum states with broken symmetry is awaiting exploration. Here, we study the angular dependence of the transport properties on the infinite-layer nickelate Nd0.8Sr0.2NiO2 superconducting films with Corbino-disk configuration. The azimuthal angular dependence of the magnetoresistance (R({\phi})) manifests the rotational symmetry breaking from isotropy to four-fold (C4) anisotropy with increasing magnetic field, revealing a symmetry breaking phase transition. Approaching the low temperature and large magnetic field regime, an additional two-fold (C2) symmetric component in the R({\phi}) curves and an anomalous upturn of the temperature-dependent critical field are observed simultaneously, suggesting the emergence of an exotic electronic phase. Our work uncovers the evolution of the quantum states with different rotational symmetries and provides deep insight into the global phase diagram of the nickelate superconductors.