Controlling the Band Filling and the Band Width in Nickelate Superconductors

TL;DR

This study systematically investigates how controlling band filling and width in nickelate superconductors affects their properties, revealing pressure and doping influences on superconductivity and possible density-wave states.

Contribution

It introduces high-pressure synthesis and transport techniques to precisely tune band parameters in nickelates, advancing understanding of their superconducting and competing phases.

Findings

Increasing NiO$_6$ tilting shifts superconductivity to higher pressure.

Hole doping reverses the pressure trend of superconductivity.

Up to three anomalies suggest density-wave formation.

Abstract

The new family of superconducting nickelates centered around La$_{3}$Ni$_{2}$O$_{7}$ possesses attractive features, such as the high transition temperature and the presence of an antiferromagnetic ground state at ambient pressure, suggesting an unconventional pairing mechanism. In the nonsuperconducting state, the possibility of different density-wave orders with opposite pressure dependencies is discussed, whose relationships and microscopic origins are largely unknown. However, sample-quality issues, such as impurity-phase formation or oxygen vacancies, impede the progress in the field. Here, we employ high-pressure synthesis and hydrostatic high-pressure transport techniques to investigate bilayer nickelates with controlled band width and filling, and perform a systematic study on their impact on the superconductivity and other characteristic properties. While increasing the tilting of the NiO$_6$ octahedra shifts the superconducting phase to higher pressure, simultaneous hole doping reverts this trend. We also observe up to three distinct anomalies in the nonsuperconducting state which are possibly related to density-wave formation.