The role of reduced dimensionality in the new perovskite superconductors

Miscellaneous · Fri Jan 01 00:00:00 EST 1993

OSTI ID:7044928

Myers, K L

Given the strong anisotropy of the copper perovskite superconductors, the question arises as to whether the superconductivity in these materials is intrinsically two-dimensional. The author's approach to this question involved making films of similar, but isotropic, material thin enough to be effectively two-dimensional. Films of doped strontium titanate were made by magnetron sputtering and pulsed laser deposition. Rutherford Backscattering X-ray diffraction show these films to be highly epitaxial with tantalum dopant atoms located predominantly on titanium sites as expected. Transport measurements reveal the importance of defect structure and impurities on the electrical properties of these doped semiconductors. Direct studies of the cuprate superconductors were later initiated. Mutual inductance and noisepower spectrum measurements were used to investigate the nature of the superconducting transition in ultrathin films of Bi[sub 2]Sr[sub 2]Ca[sub 1]Cu[sub 2]O[sub 9] (2212) and YBa[sub 2]Cu[sub 3]O[sub 7] (YBCO). Samples of different thicknesses and with different proximity layers were investigated. The apparent superconducting onset temperature is suppressed below the meanfield transition temperature and is frequency-dependent. YBCO samples with Pr[sub .5]Y[sub .5]Ba[sub 2]Cu[sub 3]O[sub 7] proximity layers have shorter penetration depths and higher transition temperatures than comparable samples with PrBa[sub 2]Cu[sub 3]O[sub 7] proximity layers. Ultrathin films of both materials show strong evidence for the existence of vortex-antivortex excitations, however, the observed superfluid response differs from Kosterlitz-Thouless predictions. The vortex diffusion follows an Arrhenius law with zero-temperature activation energies proportional to the films' inverse inductance. The author explains the results in terms of a vortex pinning model, in which the superconducting transition is a kinetic crossover dominated by vortex-pin interactions.

• Research Organization: Stanford Univ., CA (United States)
• OSTI ID: 7044928
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CUPRATES
PENETRATION DEPTH
SUPERCONDUCTIVITY
TRANSITION TEMPERATURE
PEROVSKITES
HIGH-TC SUPERCONDUCTORS
INTERMETALLIC COMPOUNDS
STRONTIUM TITANATES
ALKALINE EARTH METAL COMPOUNDS
ALLOYS
COPPER COMPOUNDS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
STRONTIUM COMPOUNDS
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
TITANATES
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
360607* - Other Materials- Superconducting Properties- (1992-)
665411 - Basic Superconductivity Studies- (1992-)