Reentrant superconductivity in Nb/Cu1-xNix bilayers.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity Research

Background:

• Superconductor/ferromagnet heterostructures are of interest for novel electronic phenomena.
• Understanding the interplay between superconductivity and magnetism in layered systems is crucial.

Purpose of the Study:

• To investigate the reentrant superconductivity phenomenon in a superconductor/ferromagnet layered system.
• To explore the influence of ferromagnetic layer thickness on superconducting properties.

Main Methods:

• Fabrication of superconductor/ferromagnetic-alloy bilayers using Niobium (Nb) and Copper-Nickel (Cu(1-x)Ni(x)).
• Systematic variation of the Cu(1-x)Ni(x) layer thickness.
• Measurement of superconducting transition temperature (T(c)) as a function of layer thickness.

Main Results:

• Observed a sharp drop in superconducting transition temperature (T(c)) with increasing Cu(1-x)Ni(x) thickness, leading to complete suppression at approximately 4 nm.
• Demonstrated the reappearance of superconductivity at larger Cu(1-x)Ni(x) thicknesses (>= 13 nm), confirming a reentrant behavior.
• Provided experimental evidence for pairing function oscillations in the ferromagnetic layer.

Conclusions:

• The study reports the first observation of pronounced reentrant superconductivity in a Nb/Cu(1-x)Ni(x) system.
• The observed phenomenon is linked to the formation of a quasi-one-dimensional Fulde-Ferrell-Larkin-Ovchinnikov-like state within the ferromagnetic layer.