Superconductivity in an ultrathin multilayer nickelate

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid-State Chemistry

Background:

• Ruddlesden-Popper nickelates are a class of materials with potential for superconductivity.
• Previous research has focused on thicker films, with less understanding of ultrathin heterostructures.

Purpose of the Study:

• To investigate the appearance of superconductivity in single-unit-cell Nd6Ni5O12.
• To understand the growth mechanisms and reduction processes critical for achieving superconductivity in ultrathin nickelates.

Main Methods:

• In situ synchrotron x-ray scattering during growth of Nd6Ni5O16.
• Growth of ultrathin Nd6Ni5O16 heterostructures.
• In situ studies of topotactic reduction.

Main Results:

• Superconductivity observed in single-unit-cell Nd6Ni5O12 with a transition temperature comparable to thicker films.
• Growth sequence deviates from the formula unit due to perovskite unit cell stability.
• Rapid formation of the square-planar phase during reduction, highly sensitive to temperature.
• Fluorite layer aids reduction by stabilizing the square-planar phase.

Conclusions:

• In situ studies are vital for understanding metastable phases in Ruddlesden-Popper nickelates.
• Precise control over growth and reduction is essential for inducing superconductivity in ultrathin films.
• The unique structure of Nd6Ni5O12 facilitates the formation of the superconducting phase.