Evidence for nodal superconductivity in infinite-layer nickelates

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• Infinite-layer nickelates are a novel class of materials exhibiting potential unconventional superconductivity.
• Determining the superconducting pairing symmetry is crucial for understanding their electronic properties.
• Previous studies have explored various nickelate compositions, but the pairing symmetry remains an open question.

Purpose of the Study:

• To investigate the superconducting pairing symmetry in infinite-layer nickelates.
• To measure the magnetic penetration depth in optimally doped La-, Pr-, and Nd-nickelates.
• To elucidate the role of magnetism in the superconducting properties of these materials.

Main Methods:

• Low-temperature measurements of magnetic penetration depth.
• Analysis of superfluid density temperature dependence.
• Synthesis and characterization of La_0.8Sr_0.2NiO₂, Pr_0.8Sr_0.2NiO₂, Nd_0.8Sr_0.2NiO₂, and Nd_0.7875Sr_0.2125NiO₂.

Main Results:

• La- and Pr-nickelates exhibit a quadratic temperature dependence of superfluid density, indicative of nodal superconductivity.
• The presence of disorder in La- and Pr-nickelates influences the superconducting nodal structure.
• Nd-nickelates display complex low-temperature behavior due to Nd 4f magnetism, hindering direct determination of nodal structure.

Conclusions:

• Nodal superconductivity is identified in La- and Pr-based infinite-layer nickelates.
• The findings suggest that disorder plays a role in the superconducting state of these materials.
• The magnetic properties of Nd-nickelates complicate the study of their superconducting pairing symmetry.