Superconducting Dome in $\mathrm{La}_{3-x}\mathrm{Sr}_{x}\mathrm{Ni}_{2}\mathrm{O}_{7-\delta}$ Thin Films

TL;DR

This study maps the phase diagram of La3-xSrxNi2O7-δ thin films, revealing a superconducting dome with a maximum Tc linked to an electron-hole crossover, providing insights into unconventional superconductivity in nickelates.

Contribution

It systematically explores the effects of Sr doping and oxygen content, unveiling a superconducting dome and associated electronic behaviors in nickelate thin films for the first time.

Findings

Superconducting dome observed with maximum Tc at specific doping levels.

Sign change in Hall coefficient coincides with maximum Tc, indicating Fermi surface reconstruction.

Resistivity behaviors resemble those in cuprates and infinite-layer nickelates.

Abstract

The ambient-pressure superconductivity in $\mathrm{La}_{3}\mathrm{Ni}_{2}\mathrm{O}_{7}$ thin films via compressive epitaxial strain provides a highly accessible platform for diverse characterization techniques, facilitating the studies of high-temperature superconductivity. Here, we systematically map the phase diagram and reveal the superconducting dome with an electron-hole crossover in compressively strained $\mathrm{La}_{3-x}\mathrm{Sr}_{x}\mathrm{Ni}_{2}\mathrm{O}_{7-\delta}$ thin films by simultaneously tuning Sr doping and oxygen content. The maximum transition temperature (${T}_{c}$) coincides with an anomalous sign change in the Hall coefficient (${R}_{H}$), reminiscent of electron-doped cuprates, which may signal a Fermi surface reconstruction. Beyond the superconducting dome, a $\ln1/T$ insulating regime and a $T$-linear resistivity regime are also resolved, resembling behaviors observed in cuprates and infinite-layer nickelates. This work reveals a dome-shaped relationship between ${T}_{c}$ and ${R}_{H}$ and establishes a key framework for understanding unconventional superconductivity in nickelate systems.