Origin of flux-flow resistance oscillations in ${\mathrm{Bi}}_2{\mathrm{Sr}}_2\mathrm{Ca}{\mathrm{Cu}}_2{\mathrm{O}}_{8+y}$: Possibility of Fiske steps in a single junction

We propose an alternative explanation to the oscillations of the flux-flow resistance found in several previously published experiments with ${\mathrm{Bi}}_2{\mathrm{Sr}}_2\mathrm{Ca}{\mathrm{Cu}}_2{\mathrm{O}}_{8+y}$ stacks. It has been argued by the previous authors that the period of the oscillations corresponding to the field needed to add one vortex per two intrinsic Josephson junctions is associated with a moving triangular lattice of vortices (out-of-phase mode), while the period corresponding to one vortex per one junction is due to the square lattice (in-phase mode). In contrast, we show that both type of oscillations may occur in a single-layer Josephson junction and thus the above interpretation is inconsistent.

Figure 1

Schematic drawing of the triangular lattice (a) corresponding to the out-of-phase fluxon mode and the square lattice (b) associated with the in-phase fluxon mode.

Figure 2

Current-voltage characteristics of a long junction $(N=1)$ with parameters $\ell =40$, $\alpha =0.1$, and $h=4$. Arrows indicate switching between branches for rising and decreasing bias current $\gamma$.

Figure 3

(Color online) Differential flux-flow resistance $\mathrm{d}V∕\mathrm{d}\gamma$ versus magnetic field $h$ for the single junction $(N=1)$ with $\ell =40$ and $\alpha =0.1$ at constant bias current $\gamma =0.3$.

Figure 4

(Color online) Flux-flow static resistance $V∕\gamma$ (thick curve) and differential resistance $\mathrm{d}V∕\mathrm{d}\gamma$ (thin curve) versus magnetic field $h$ for the same junction as in Fig. 3 at a lower bias current $\gamma =0.2$.

Figure 5

(Color online) Differential flux-flow resistance $\mathrm{d}V∕\mathrm{d}\gamma$ at constant bias current $\gamma =0.2$ versus magnetic field $h$ calculated directly from Eq. (6) with parameters $\ell =40$ and $\alpha =0.1$. The voltage is multiplied by a factor $\ell ∕\pi$ to make its scale identical to the voltage normalization used in the previous figures.