Extrinsic or intrinsic conduction in cuprates: Anisotropy, weak, and strong links

Journal Article · Fri Oct 01 04:00:00 EDT 1993 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.48.9735· OSTI ID:6072995

Halbritter, J ^[1]

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1. Kernforschungszentrum Karlsruhe, IMFI, Postfach 3640, 76021 Karlsruhe (Germany)

The layered structure of superconducting cuprates is the origin of the anisotropic conductivity in the normal state and the anisotropic energy gap and anisotropic critical current density [ital j][sub [ital c]] in the superconducting state. The anisotropic, quasi-two-dimensional conduction in the CuO[sub 2] planes is close to the metal-insulator transition. Defects can either initiate insulating or conducting behavior depending on the position of the defects and orientation of the current. For example, defects may enhance the small conductivity [sigma][sup [perpendicular]] perpendicular to the planes, whereas defects reduce the strong conductivity [sigma][sup [parallel]] along the planes. That is, defects make the cuprate superconductors more isotropic. Due to the layered structure defects are often organized in planes, usually of reduced conductivity, which are named weak links'' (WL). The effect of WL on the dc conductivity and superconductivity, especially as function of temperature and field, allows their classification and quantification. Their grain-boundary resistances [ital R][sub [ital b][ital n]][sup [parallel]][ge]10[sup [minus]7]--10[sup [minus]9] [Omega] cm[sup 2] are several orders of magnitude larger than the metallic Sharvin resistance, proving that WL are insulating interruptions. They contain localized states carrying current across by resonant tunneling. Such WL deteriorate the metallic conductivity [sigma][sup [parallel]], the superconducting critical current [ital j][sub [ital c]][sup [parallel]], and the energy gap [Delta][sub [ital s]][sup [parallel]], but enhance the leakage current [ital j][sub [ital b][ital l]][sup [parallel]].

• OSTI ID: 6072995
• Journal Information: Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 48:13; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

665411* -- Basic Superconductivity Studies-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANISOTROPY
COPPER COMPOUNDS
CRITICAL CURRENT
CUPRATES
CURRENTS
ELECTRIC CONDUCTIVITY
ELECTRIC CURRENTS
ELECTRICAL PROPERTIES
ENERGY GAP
HIGH-TC SUPERCONDUCTORS
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SUPERCONDUCTORS
TEMPERATURE DEPENDENCE
TRANSITION ELEMENT COMPOUNDS