Quantum stability and superconducting properties of ultrathin alloy films made from bulk immiscible elements: Pb and Ga

E. J. Moon; M. M. Özer; Y. Jia; G. Duscher; J. R. Thompson; Z. Y. Zhang; H. H. Weitering

doi:10.1103/PhysRevB.84.125415

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Quantum stability and superconducting properties of ultrathin alloy films made from bulk immiscible elements: Pb and Ga

E. J. Moon, M. M. Özer, Y. Jia, G. Duscher, J. R. Thompson, Z. Y. Zhang, H. H. Weitering

DOI 10.1103/PhysRevB.84.125415 · Physical Review B

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Abstract

Pb and Ga are immiscible in bulk form. Here, we show that atomically smooth Pb1−xGax (x≈ 0.06) alloy films can be stabilized on a Si(111)-7×7 substrate by quantum confinement. Similar to the case of pure Pb, the alloy films follow a bilayer-by-bilayer growth mode but the resulting quantum growth morphology is remarkably different. Their superconducting transition temperatures indicate hole doping, supporting the notion that Ga atoms are substitutionally incorporated. The critical current densities are very high and exhibit a unique nonmonotonic temperature dependence. This critical current anomaly is a direct consequence of the exceptional film morphology and is attributed to a superconducting transition inside two-monolayer thick vortex pinning centers.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Pb0.94Ga0.06 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	7	Pressure not reported	onset
Pb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	7.2	Pressure not reported	onset
Pb1-xBix Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	7.7	Pressure not reported	onset
Pb1-xBix Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	8.05	Pressure not reported	onset