BEGIN:VCALENDAR VERSION:2.0 CALSCALE:GREGORIAN PRODID:UW-Madison-Physics-Events BEGIN:VEVENT SEQUENCE:0 UID:UW-Physics-Event-2127 DTSTART:20110221T223000Z DURATION:PT1H0M0S DTSTAMP:20260420T134703Z LAST-MODIFIED:20110216T204519Z LOCATION:5310 Chamberlin SUMMARY:Origin of 1/f magnetic noise in superconducting circuits\, Con densed Matter Theory Group Seminar\, Kostyantyn Kechedzhi\, Rutgers Un iversity DESCRIPTION:We analyze recent experimental data on the complex inducta nce of dc SQUIDs that show 1/f inductance noise that is highly correla ted with conventional 1/f flux noise. We argue that there are two mech anisms likely to give rise to the observed inductance noise: fluctuati ons in the kinetic inductance of superconducting wires caused by the d ynamics of scattering centers\; and the dynamics of unpaired spins of electrons localized on or close to the surface of the superconducting wires. We analyze both possibilities in detail and conclude that the l atter is likely to be dominating in the experiments. Moreover\, we arg ue that the experimental data imply a formation of long range order in fractal spin structures on the surface of the superconducting wiring. We show that such structures appear naturally in a random system of s pins with wide distribution of spin-spin interactions. We perform nume rical simulations on the simplest model of this type and show that it exhibits 1 / f1 + ζ magnetization noise with small expone nt ζ and reproduces the correlated behavior observed experimentally. URL:https://www.physics.wisc.edu/events/?id=2127 END:VEVENT END:VCALENDAR