Noise and capacitive effects in 2D Josephson Juntion arrays: Voltage rectification effects

M. F. CARUSELA Y V .P. RAMUNNI

Buenos Aires, Argentina

Workshop; "3rd Workshop on Quantum Chaos: Theory and Applications", dedicated to the 65th birthday of Marcos Saraceno, december 2009.; 2009

CNEA - Dpto. Física Tandar

In the past few years considerable attention has been paid to the mechanisms responsible for the ratchet effects in Josephson systems. A net flux of particles driven by a zero average alternating excitation results from the interaction of the media  with an asymmetric potential. This behavior has also been theoretically predicted and experimentally corroborated for the motion of quantum flux lines in superconducting systems. A nonzero dc voltage even when an ac excitation is sent through the superconductor, thus acting as a rectified voltage. Recently, Marconi et al [Phys. Rev. B,  76, 224501 (2007)], have been demostrate the influence of the position of the current or voltage probes on the resultant rectification effect in microsized superconducting triangles. They show that an ac current injected above the geometrical center of the triangle gives an opposite rectification signal than for current injection below the geometrical center of the triangle. In addition, a lower signal is obtained if the contacts are attached along a median of the triangle so that upper and lower parts of the triangle are symmetric around this line. In this work, we study voltage rectification effects in mesoscopic superconducting triangles observed by Marconi, using the resistively  shunted junction (RSJ) model [Mon et al, Phys. Rev. Lett.  62, 673 (1989)] including both capacitive effects and thermal noise. We solve numerically the superconducting phase dynamics considering a closed loop with a finite number of identical Josephson junctions in presence of an externally applied currents and persistent currents induced by magnetic field. As a consequence of the superposition of these currents,   clear   voltage   rectification   effects   are   observed.   We   test   our   prdictions   in   rectification experiments on 2D JJA were reported by Shalom and Pastoriza [Shalóm et al, Phys. Rev. Lett. 94, 177001 (2005)].