Observation of Josephson-like tunneling junction characteristics and positive magnetoresistance in Oxygen deficient Nickelate films of $Nd_{0.8}Sr_{0.2}NiO_{3-\delta}$

TL;DR

This study reports Josephson-like tunneling and positive magnetoresistance in oxygen-deficient Nd0.8Sr0.2NiO3-δ films, suggesting possible superconductivity and novel transport phenomena in nickelate materials.

Contribution

First observation of Josephson-like tunneling and positive magnetoresistance in oxygen-deficient nickelate films, indicating potential superconductivity and new transport mechanisms.

Findings

Josephson-like tunneling junction characteristics observed

Positive magnetoresistance detected in the films

Evidence supporting superconductivity in nickelate films

Abstract

Nickelate films have recently attracted broad attention due to the observation of superconductivity in the infinite layer phase of $Nd_{0.8}Sr_{0.2}NiO_2$ (obtained by reducing Sr doped $NdNiO_3$ films) and their similarity to the cuprates high temperature superconductors. Here we report on the observation of a new type of transport in oxygen poor $Nd_{0.8}Sr_{0.2}NiO_{3-\delta}$ films. At high temperatures, variable range hopping is observed while at low temperatures a novel tunneling behavior is found where Josephson-like tunneling junction characteristic with serial resistance is revealed. We attribute this phenomenon to coupling between superconductive (S) surfaces of the grains in our Oxygen poor films via the insulating (I) grain boundaries, which yields SIS junctions in series with the normal (N) resistance of the grains themselves. The similarity of the observed conductance spectra to tunneling junction characteristic with Josephson-like current is striking, and seems to support the existence of superconductivity in our samples.