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Thermal conductivity of high-temperature superconductors

Thesis/Dissertation ·
OSTI ID:5401214
The investigation is naturally categorized into two temperature ranges: very low temperatures, {approximately}0.06K < T < {approximately}6K, and in the temperature range 6K < T < 250K. For very low temperatures, a unified description of the thermal conductivity, {kappa}, of high-temperature superconductors is not yet established. An expected T{sup 3} dependence is not obeyed, and deviations from this dependence can be divided into two categories: (1) A power law dependence weaker than cubic, and (2) An anomalous linear temperature dependence for T < {approximately} 0.5K. The possible origin of both phenomena is discussed. For temperatures near the superconducting transition temperature, the behavior of {kappa} for the Bi-O based superconductor, Ba{sub 1{minus}x}K{sub x}BiO{sub 3}, is dramatically different than that of the Cu-O based superconductors. In the Ba{sub 1{minus}x}K{sub x}BiO{sub 3} system, a decrease in {kappa} is observed as the temperature is lowered below {Tc}. In contrast, for CuO-based superconductors, a marked increase in {kappa} is observed as the temperature is lowered below {Tc}. This effect is particularly dramatic for the YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} single crystals, and a theoretical model is presented to describe the data of this system. Finally, it is shown that the thermal conductivity of single-crystal YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} is sensitive to a magnetic field.
Research Organization:
Michigan Univ., Ann Arbor, MI (United States)
OSTI ID:
5401214
Country of Publication:
United States
Language:
English