Reducing the strain required for ambient-pressure superconductivity in bilayer nickelates

TL;DR

This paper demonstrates that applying nearly half the strain previously required enables ambient-pressure superconductivity in bilayer nickelates, facilitating studies of their phase diagram and underlying physics.

Contribution

It reports the growth of bilayer nickelate films on LaAlO3 with reduced strain, achieving superconductivity at ambient pressure and providing a platform to explore phase boundaries.

Findings

Superconductivity onset above 10 K in strained films

Zero resistance achieved at 3 K

Strain nearly halved to -1.2% compared to previous methods

Abstract

The remarkable discovery of high temperature superconductivity in bulk bilayer nickelates under high pressure has prompted the conjecture that epitaxial compressive strain might mimic essential aspects of hydrostatic pressure. The successful realization of superconductivity in films on SrLaAlO4 (001) (SLAO) supports this correspondence, yet it remains unclear whether the rich pressure-temperature phase diagram of bilayer nickelates can be systematically mapped (and studied at ambient pressure) as a function of epitaxial strain. To this end, experimental access near the elusive edge of the superconducting phase boundary would provide invaluable insight into the nature of the superconducting state and the ground state from which it emerges. It would also offer a benchmark for theoretical models. Here we report superconducting bilayer nickelates grown on LaAlO3 (001) (LAO), where the compressive strain required for ambient-pressure superconductivity is nearly halved to -1.2%. These films exhibit a superconducting onset above 10 K and reach zero resistance at 3 K, with normal-state transport properties differing from those of films grown on SLAO. Our results offer a new opportunity to probe emergent phenomena near the superconducting phase boundary in the strain-temperature phase diagram of bilayer nickelates.