The Quest for High-Temperature Superconductivity in Nickelates under Ambient Pressure

Area of Science:

• Materials Science
• Condensed Matter Physics
• Superconductivity Research

Background:

• Superconductivity near 80 K was recently observed in lanthanum nickelate (La₃Ni₂O₇) but only under extreme hydrostatic pressure (>14 GPa).
• Stabilizing this high-temperature superconductivity at ambient pressure is crucial for practical applications.
• Substitution of lanthanum with barium was proposed as a potential strategy to achieve this stabilization.

Purpose of the Study:

• To investigate the feasibility of stabilizing superconductivity in (La_1-xBa_x)₃Ni₂O₇ at ambient pressure.
• To synthesize and characterize thin films of (La_1-xBa_x)₃Ni₂O₇ with varying barium content and cation distribution.

Main Methods:

• Utilized the atomic-layer-by-layer molecular beam epitaxy (ALL-MBE) technique.
• Synthesized thin films of (La_1-xBa_x)₃Ni₂O₇ with systematic variations in barium substitution (x) and La/Ba distribution.

Main Results:

• None of the synthesized (La_1-xBa_x)₃Ni₂O₇ compositions could be stabilized epitaxially.
• The targeted compounds decomposed immediately upon synthesis, forming a mixture of other phases.
• Failed to achieve stable films for ambient pressure superconductivity studies.

Conclusions:

• The proposed method of substituting lanthanum with barium in La₃Ni₂O₇ is not a viable route to stabilize ambient pressure superconductivity.
• This specific approach to achieving high-temperature superconductivity in nickelates at ambient pressure appears unpromising.
• Further research into alternative strategies for stabilizing nickelate superconductivity is warranted.