Dresden 2006 – scientific programme
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TT: Tiefe Temperaturen
TT 11: Superconductivity: Heterostructures, Andreev Scattering, Proximity Effect, Coexistence
TT 11.10: Talk
Tuesday, March 28, 2006, 12:00–12:15, HSZ 301
Effect of Microwaves on the Current-Phase-Relation of diffusive SNS Junctions — •Martin Füchsle, Johannes Bentner, Peter Tranitz, Werner Wegscheider, and Christoph Strunk — Institut für experimentelle und angewandte Physik, Universität Regensburg
We investigate the current-phase-relation (CPR) of long diffusive
superconductor - normal metal - superconductor (SNS) Josephson
junctions under microwave irradiation. In contrast to earlier
experiments that focused on the I-V characteristics of
current-biased junctions, we directly measure the full CPR by means
of Micro-Hall-Magnetometry. The measurements are done in the
high-temperature regime ETh<kBT ≪ Δ, where ETh is the Thouless energy and ℏ ω ≈ ETh.
We find that the occupation of the Andreev states in the N region
can be strongly affected by microwave radiation. A strong deviation
of the CPR from the well-known sinusoidal I(Φ) relation is
observed: depending on the applied frequency and amplitude, the
supercurrent can be strongly suppressed and the maximum current can
appear at phase differences smaller than π/2. At some
frequencies, the sin(Φ) term in the CPR can be completely
suppressed, resulting in a dominant second harmonic. The results may
be qualitatively interpreted in terms of a simple model for the
spectrum of low-lying Andreev bound states.