Interplay between superconductivity and ferromagnetism in epitaxial Nb(110)/Au(111)/Fe(110) trilayers

TL;DR

This study investigates how ferromagnetism influences superconductivity in epitaxial Nb/Au/Fe trilayers, revealing complex quantum interference effects and periodic Tc variations dependent on Au layer thickness.

Contribution

It demonstrates a novel quantum interference phenomenon affecting superconductivity in epitaxial trilayers, not explained by existing models like Fermi surface nesting or FFLO oscillations.

Findings

Strong Tc suppression for Au thickness <10 Å.

Periodic Tc variation with a ~21 Å period for 20 Å < tAu < 104 Å.

Evidence of a new quantum interference effect in clean trilayer systems.

Abstract

In order to clarify the influence of ferromagnetism on superconductivity through a normal metal layer, the superconducting properties of epitaxial Nb(110)/Au(111)/Fe(110) trilayers were studied as a function of the thickness tAu of the intervening Au layer. Structural characterization of the samples revealed sharp interfaces, almost free from roughness. A strong suppression of the superconducting transition temperature Tc was observed for tAu<10 A, implying a strong spin-polarization of the Au layer in the vicinity of the Au/Fe interface. A periodic change of Tc with a period of ~21 A (~9 atomic monolayer of Au) was observed for 20 A<tAu<104 A. Neither the Fermi surface nesting of the normal metal layer, nor Fulde-Ferrel-Larkin-Ovchinnikov oscillations induced by a superconducting proximity effect in the ferromagnet can by themselves account for the observed period. These results suggest that a new and more subtle form of quantum interference occurs in very clean trilayer systems.