Transport properties of clean and disordered Josephson-junction arrays

We investigate the influence of quantum fluctuations and weak disorder on the vortex dynamics in a two-dimensional superconducting Berezinskii-Kosterlitz-Thouless system. The temperature below which quantum fluctuations dominate the vortex creep is determined and the transport in this quantum regime is described. The crossover from quantum to classical regime is discussed and the quantum correction to the classical current-voltage relation is determined. It is found that weak disorder can effectively reduce the critical current as compared to that in the clean system.

Figure 1

Potential barrier for the separation of the vortex-antivortex pair.

Figure 2

Dynamic phase diagram in current-temperature coordinates showing different types $V\left(j,T\right)$ dependencies for $T<T_{\text{BKT}}$. The dashed and the solid lines sketch $T_0\left(j\right)$ and $T^{\ast }\left(j\right)$, respectively. In the domain $T<T_0$ quantum tunneling of vortices dominates the vortex dynamics while at $T>T^{\ast }$ the voltage-current characteristics is determined by the thermally activated motion. In the shaded region the quantum correction to the classical result, given by Eq. (17), applies.