1997/04/13 by Ing-Jye Hwang, Seungoh Ryu, D. Stroud · 1 citation
Physics and Astronomy · #Physics of Superconductivity and Magnetism #Quantum and electron transport phenomena #Theoretical and Computational Physics #cond-mat.stat-mech #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.57.6036
12 pages, RevTeX, eight figures in postscript
arxiv created 1997/04/13 · openalex publication_date 1998/03/01 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We study the vortex number noise Sv(\ensuremathω) and fluctuation conductivity \ensuremathσ1(\ensuremathω) in two-dimensional Josephson-junction arrays at three different applied magnetic fields, corresponding to zero, one-half, and (1)/(24) of a flux quantum per plaquette (f=0, (1)/(2) and (1)/(24)). Sv and \ensuremathσ1 are obtained by numerically solving the equations for the coupled overdamped resistively-shunted-junction model with Langevin noise to simulate the effects of temperature. In all three cases, we find that Sv(\ensuremathω)\ensuremath∝\ensuremathω^\ensuremath-3/2 at high frequencies \ensuremathω and flattens out to become frequency independent at low \ensuremathω, indicative of vortex diffusion, while \ensuremathσ1\ensuremath∼\ensuremathω^\ensuremath-2 at sufficiently high \ensuremathω and \ensuremath∼\ensuremathω0 at low frequencies. Both quantities show clear evidence of critical slowing down and a simplified scaling behavior near the normal-to-superconducting transitions at f=0 and f=(1)/(2), indicating that the vortex diffusion coefficient is approaching zero and the charge-carrier relaxation time is diverging at these temperatures. At f=(1)/(24), there is no clear phase transition; instead, the vortex diffusion coefficient diminishes continuously as the temperature is lowered towards zero. The critical slowing down of Sv(\ensuremathω), but not its frequency dependence, is in agreement with recent experiments on the flux noise S_\ensuremathΦ(\ensuremathω) in Josephson-junction arrays, which show a 1/\ensuremathω frequency dependence. We speculate about some possible reasons for the absence of a 1/\ensuremathω frequency regime.