Anisotropic phase stiffness in infinite-layer nickelates superconductors.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• Phase stiffness is a critical parameter governing superconductivity in unconventional materials like cuprates and iron-based superconductors.
• Understanding phase stiffness anisotropy is key to unlocking the mechanisms behind high-temperature superconductivity.

Purpose of the Study:

• To investigate and reveal the anisotropic phase stiffness in infinite-layer nickelate superconductors.
• To compare the anisotropic properties of nickelates with those of cuprate superconductors.

Main Methods:

• Utilized a vector current technique for in-situ angle-resolved transport measurements.
• Analyzed in-plane resistance anisotropy in both normal and superconducting states.
• Measured electric conductivity and phase stiffness as a function of current direction relative to crystal axes.

Main Results:

• Demonstrated pronounced in-plane resistance anisotropy in Nd0.8Sr0.2NiO2, indicating crystal symmetry breaking.
• Observed peak electric conductivity at 125°, evolving to 160° near the zero-resistance temperature.
• Found that phase stiffness maximizes along 160°, a direction independent of electronic nematicity and crystal lattice symmetry.

Conclusions:

• The anisotropic phase stiffness in nickelates exhibits distinct characteristics compared to their crystal and electronic symmetry axes.
• Identical measurements on cuprates yielded consistent results, suggesting shared principles in unconventional superconductivity.
• Findings provide a basis for a unified theoretical framework for understanding both nickelate and cuprate superconductors.