Dynamical properties of two-dimensional Josephson junction arrays

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1990

OSTI ID:5997013

Benz, S P

The dynamical properties of two-dimensional (2D) Josephson junction arrays are investigated at temperatures below the Kosterlitz-Thouless phase transition. A comprehensive study, based on experiments and simulations, is completed, on 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-effect junctions that were fabricated using various photolithographic and thin-film deposition techniques. A complete explanation of the dynamic resistance in arrays is presented 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 q x q unit cells. Prominent peaks in the dynamic resistance are observed for these commensurate magnetic fields, and the currents at these peaks are related 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. When RF currents are applied to the 2D arrays in commensurate magnetic fields, fractional giant steps appear in the current-voltage curves at voltages, V(sub n) = n(N/q)h(nu)/2e, (where N = 1000 is the number of junctions in the direction of applied current) directly related to the vortex superlattice unit cell size, q. These steps are confirmed through computer simulations. A phenomenological model is proposed to explain these steps. The results of simulations of positionally-diordered superconducting wire networks are also presented.

• Research Organization: Harvard Univ., Cambridge, MA (USA)
• OSTI ID: 5997013
• Country of Publication: United States
• Language: English

Related Subjects

656100* -- Condensed Matter Physics-- Superconductivity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
COMPUTERIZED SIMULATION
COPPER
CURRENTS
DATA
DEPOSITION
DIRECT CURRENT
ELECTRIC CONDUCTIVITY
ELECTRIC CURRENTS
ELECTRIC POTENTIAL
ELECTRICAL PROPERTIES
ELEMENTS
FILMS
INFORMATION
JOSEPHSON JUNCTIONS
JUNCTIONS
MAGNETIC FIELDS
MATHEMATICAL MODELS
METALS
NIOBIUM
NUMERICAL DATA
OSCILLATIONS
PHYSICAL PROPERTIES
SIMULATION
SUPERCONDUCTING JUNCTIONS
SUPERCONDUCTIVITY
SUPERLATTICES
THEORETICAL DATA
THERMODYNAMIC PROPERTIES
THIN FILMS
TRANSITION ELEMENTS
TRANSITION TEMPERATURE
VORTICES