Half-Integer Shapiro Steps at the 0−π Crossover of a Ferromagnetic Josephson Junction

Hermann Sellier; Claire Baraduc; François Lefloch; Roberto Calemczuk

doi:10.1103/PhysRevLett.92.257005

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Half-Integer Shapiro Steps at the 0−π Crossover of a Ferromagnetic Josephson Junction

Hermann Sellier, Claire Baraduc, François Lefloch, Roberto Calemczuk

DOI 10.1103/PhysRevLett.92.257005 · Physical Review Letters

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Abstract

We investigate the current-phase relation of S/F/S junctions near the crossover between the 0 and the π ground states. We use Nb/CuNi/Nb junctions where this crossover is driven both by thickness and temperature. For a certain thickness a nonzero minimum of critical current is observed at the crossover temperature. We analyze this residual supercurrent by applying a high frequency excitation and observe the formation of half-integer Shapiro steps. We attribute these fractional steps to a doubling of the Josephson frequency due to a sin(2ϕ) current-phase relation. This phase dependence is explained by the splitting of the energy levels in the ferromagnetic exchange field.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown