The thermal conductivity of lead at low temperature
Wolff, Charles Lambert
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https://hdl.handle.net/2142/16639
Description
Title
The thermal conductivity of lead at low temperature
Author(s)
Wolff, Charles Lambert
Issue Date
1961
Doctoral Committee Chair(s)
Mapother, D.E.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
lead
thermal conductivity
Language
en
Abstract
Detailed low temperature thermal conductivity measurements have been made in the superconducting and normal states of Pb samples with impurities < .05 atomic percent. These measurements have been combined with Olsen’s data on Pb-Bi alloys to display an isothermal relation between the strength of point defect scattering and the ratio, Ks /Kn, of the thermal conductivity in the two states. As long as only electron conductivity is important, Ks/Kn varies linearly with the square root of the ratio, r, of point defect scattering resistance to phonon scattering resistance in the normal state. This relation also holds for the Hg data of Hulm. The specimens studied had values of r ranging from .02 to 2.
An extrapolation to r = 0 of this linear relation provides curves which are interpreted as the temperature dependence of Ks /Kn in perfectly pure Ph and Hg. These curves do not agree with the theory of Kadanoff and Martin unless it is assumed that the energy gap at absolute zero is 7.3 kTc, which is almost twice that indicated by other experiments. As has been observed before in these metals, Ks /Kn is also not explained by the theory of Bardeen, Rickayzen, and Tewordt.
The thermal magneto-resistance of Pb has been measured in longitudinal field and compared with Mendelssohn and Rosenberg's results. The longitudinal and tranverse resistance appear to approach each other above 40K in Pb, while below this temperature their behaviors are radically different. An attempt' to identity isotope scattering of phonons in the superconducting state proved inconclusive.
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