Dynamical Properties of Two-Dimensional Josephson Junction Arrays
Abstract
We have investigated the dynamical properties of two dimensional (2D) Josephson junction arrays at temperatures below the Kosterlitz-Thouless phase transition. We have completed a comprehensive study, based on experiments and simulations, of the effects of large direct dc and radio-frequency rf bias currents on 2D arrays in the presence of perpendicular magnetic fields. Experiments were performed on large 1000 by 1000 arrays of Nb-Cu-Nb proximity- effects junctions that were fabricated using various photolithographic and thin- film deposition techniques. We present a complete explanation of the dynamic resistance in arrays as a function of both dc bias current and magnetic field. For certain fields, when the number of flux quanta per array unit cell is the ratio of two integers, the field-induced vortices are commensurate with the array and are arranged in ordered superlattices with qxq unit cells. Prominent peaks in the dynamic resistance are observed for these commensurate magnetic fields, and we relate the currents at these peaks with the depinning currents of the vortex superlattices. New exact calculations of the critical current are presented for the cases where f=1/2 and 1/3, which agree well with previous theoretical results and our experimental measurements.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1990
- Accession Number
- ADA223965
Entities
People
- Samual P. Benz
Organizations
- Harvard University