Dynamics of granular superconductors at zero and large magnetic fields: Glassy behavior

Journal Article · Fri Nov 01 00:00:00 EST 1991 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.44.9643· OSTI ID:6132205

Wang, Z Q; Stroud, D ^[1]

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1. Department of Physics, Ohio State University, Columbus, Ohio (USA)

We calculate the transport properties of a model granular superconductor in zero magnetic field and in a strong random magnetic field. The Hamiltonian is taken as the sum of two terms: a Josephson interaction coupling neighboring phases and a diagonal charging energy. The noncommutativity of charge and phase is neglected (classical, or large-grain, limit), as is dissipation occurring through shunt resistances connecting neighboring grains. The dynamical properties, including current-current correlation functions, conductivities, and voltage noise, are calculated as a function of temperature via molecular-dynamics techniques. For a simple-cubic lattice in zero magnetic field, the model exhibits the expected insulator-to-superconductor transition near {ital T}{sub {ital c}}=2.2{ital E}{sub {ital J}}/{ital k}{sub {ital B}}, where {ital E}{sub {ital J}} is the Josephson coupling energy. The frequency-dependent conductivity has a strong fluctuation peak near {ital T}{sub {ital c}}. Its behavior above {ital T}{sub {ital c}} is qualitatively reproduced by a simple Aslamasov-Larkin-like model. The voltage noise has a time correlation function, which oscillates below {ital T}{sub {ital c}} but falls off nearly monotonically above {ital T}{sub {ital c}}. Its low-temperature behavior is explained analytically in terms of a model of voltage fluctuations due to propagating phase waves. A disordered system in a strong magnetic field is modeled by grains on a simple-cubic lattice with random magnetic phase factors on each bond, following Huse and Seung. Evidence for a vortex-fluid-to-vortex-glass transition is found from the increasingly slow decay of the current-current correlation function above {ital T}{sub {ital g}}{approx}0.45{ital E}{sub {ital J}}/{ital k}{sub {ital B}}, and from its nonergodic behavior below {ital T}{sub {ital g}}.

• DOE Contract Number: FG02-90ER45427
• OSTI ID: 6132205
• Journal Information: Physical Review, B: Condensed Matter; (United States), Vol. 44:17; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
SUPERCONDUCTING COMPOSITES
ELECTRIC CONDUCTIVITY
CRITICAL CURRENT
CRITICAL TEMPERATURE
FLUCTUATIONS
GRANULAR MATERIALS
HAMILTONIANS
JOSEPHSON JUNCTIONS
COMPOSITE MATERIALS
CURRENTS
ELECTRIC CURRENTS
ELECTRICAL PROPERTIES
JUNCTIONS
MATERIALS
MATHEMATICAL OPERATORS
PHYSICAL PROPERTIES
QUANTUM OPERATORS
SUPERCONDUCTING JUNCTIONS
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
VARIATIONS
665411* - Basic Superconductivity Studies- (1992-)