Interlayer-Coupling-Driven High-Temperature Superconductivity in La_{3}Ni_{2}O_{7} under Pressure.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Chemistry

Background:

• High-temperature superconductivity discovered in La_{3}Ni_{2}O_{7} under pressure.
• Electronic properties are governed by bilayer NiO_{2} planes with interlayer 3d_{z^{2}} orbital bonding.
• Low-energy physics involves intralayer (J∥) and interlayer (J⊥) spin-exchange interactions.

Purpose of the Study:

• To investigate the role of interlayer coupling (J⊥) in the superconducting properties of La_{3}Ni_{2}O_{7}.
• To model the electronic behavior using a single-orbital bilayer t-J model.
• To understand the transition between d-wave and s-wave superconductivity.

Main Methods:

• Development of a single-orbital bilayer t-J model from a multi-orbital model.
• Incorporation of Hund's rule and integration of the 3d_{z^{2}} spin degree of freedom.
• Application of the slave-boson approach to solve for bonding and pairing order parameters.

Main Results:

• Interlayer coupling (J⊥) transitions the superconducting state from d-wave to s-wave near 1/4 filling.
• Strong J⊥ enhances interlayer superconducting order, significantly increasing the critical temperature (Tc).
• A possible coexistence of s-wave and d-wave superconducting states (s+id) was identified.

Conclusions:

• The interlayer coupling (J⊥) is crucial for tuning the superconducting symmetry and critical temperature in La_{3}Ni_{2}O_{7}.
• The slave-boson approach effectively models the complex electronic interactions in this material.
• The findings provide a theoretical basis for exploring enhanced superconductivity in layered nickelates.