Orientational pinning and transverse voltage: Simulations and experiments in square Josephson junction arrays

V. I. MARCONI; S. CANDIA; P. BALENZUELA; H. PASTORIZA; D. DOMINGUEZ; P. MARTINOLI

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

The American Physical Society

Año: 2000 vol. 62 p. 4096 - 4104

0163-1829

We study the dependence of the transport properties of square Josephson Junctions arrays with the direction of the applied dc current, both experimentally and numerically.  We present computational simulations of current-voltage curves at finite temperatures for a singlevortex in an array of $L imes L$ junctions ($Ha^2/Phi_0=f=1/L^2$), and experimental measurementsin $100 imes1000$ arrays under a low magnetic field corresponding to $fapprox0.02$. We find that the transverse voltage vanishes only inthe directions of maximum symmetry of the square lattice:the [10] and [01] direction (parallel bias) and the[11] direction (diagonal bias).For orientations different than the symmetry directions, we find afinite transverse voltage which depends strongly on the angle $phi$ of the current. We find that vortex motion is pinned in the [10] direction ($phi=0$), meaning that  the voltage response isinsensitive to small changes in the orientation of the current near$phi=0$.We call this phenomenon orientational pinning. This leadsto a finite transverse critical current for a bias at $phi=0$ and toa transverse voltage for a bias at $phi ot=0$.On the other hand, for diagonal bias in the [11] directionthe behavior is highly unstable against small variations of $phi$, leading to a rapid change from zerotransverse voltage to a large transverse voltage within a few degrees.This last behavior is in good agreement with our measurements in arrayswith a quasi-diagonal current drive.