Noise and chaos in driven Josephson junctions

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1987

OSTI ID:6710357

Hu, Q

The response of several Nb-aSi-Nb junctions to laser radiation are studied at far-infrared frequencies, 245, 419, and 604 GHz. At 419 GHz, which is close to the plasma frequencies of the junctions (approx. 400GHz), rich nonlinear dynamic effects are exhibited in the dc I-V characteristics, such as, negative-resistance regions, subharmonic steps, and noisy I-V curves. By using a RSJ model, modified to include a piecewise nonlinear resistance, with an appropriate amount of noise, the dc I-V curves of the irradiated junctions can be reproduced accurately in both digital and analog simulations. It was discovered in simulations that the noisy I-V curves are caused by various nonlinear dynamic effects. There are I-V curves measured at certain laser power levels showing intrinsic chaos. On the other hand, there are some noisy regions in the experimental I-V curves do not show intrinsic chaos in the noise-free simulations, but instead show the coexistence of two or more attractors. Adding noise comparable to that in the experiment makes the system switch randomly between the attractors, thus producing noisy I-V curves indistinguishable from those of intrinsically chaotic ones.

• Research Organization: Harvard Univ., Cambridge, MA (USA)
• OSTI ID: 6710357
• Country of Publication: United States
• Language: English

Related Subjects

420201* -- Engineering-- Cryogenic Equipment & Devices
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ELECTRICAL PROPERTIES
JOSEPHSON JUNCTIONS
JUNCTIONS
NOISE
NONLINEAR PROBLEMS
PHYSICAL PROPERTIES
PHYSICAL RADIATION EFFECTS
RADIATION EFFECTS
SUPERCONDUCTING JUNCTIONS