A resonance structure was observed in the current-voltage curves of overdamped long 0–32°[001]-tilt ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_7$ bicrystal grain-boundary junctions (GBJ’s), and is attributed to a Josephson flux-flow resonance. The voltage position of the resonance moves almost linearly from 0.5 to 2 mV with an applied magnetic field. From this linear dependence and using the London penetration depth ${\lambda }_{\mathit{L}}$=140 nm, we determined the ratio between the effective dielectric thickness and the relative dielectric constant t/${\mathrm{\varepsilon }}_{\mathit{r}}$≊0.3 nm, and the quasiparticle loss coefficient α=1.3 at 16 K for a 30-μm long junction. The loss increases with temperature and no resonance was seen at 77 K. The perturbed sine-Gordon equation was used for modeling long GBJ’s. Simulations support the experimental observation that Josephson vortices can propagate unidirectionally in an overdamped, homogeneous junction up to α≊2.

• Received 21 November 1994

DOI:https://doi.org/10.1103/PhysRevB.51.8684