Browsing by Author "Ho, J. C."

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Low-temperature specific heat of superconductors - I. Historical perspective prior to 1986
(2019-10-01)
Ho, J. C.
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Lin, J. G.
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Lin, J. Y.
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Yang, H. D.
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交大名義發表
Specific heat is a fundamental thermodynamic quantity closely related to internal energy and entropy of a system. In superconductivity research, it has been playing important roles ever since the intriguing critical phenomenon was discovered. Looking back, though, calorimetric measurements, along with the relevant low-temperature techniques, improved slowly over decades. Erroneous conclusions were reached often in the beginning, but eventually several calorimetrically-derived key features formed part of the basis in the microscopic BCS theory and its extended versions. While unable to predict whether or when a given material would become superconducting, theories helped data analysis and guided new superconductors search. Many elements, alloys and compounds joined the long list of known superconductors over the 75-year period between 1911 and 1986. Specific heat data yielded characteristic parameters, and ascertained whether an observed transition was a bulk effect. In the later years, theoretical models or experimental results also revealed a few classes of unconventional superconductors, mostly involving the interplay between superconductivity and magnetism. This article is purposely focused, as historical perspective, on how such activities progressed. Only initial findings and some related reports are cited, leaving out much more detailed and better executed work published later. For the same reason, only select figures and discussions of cited articles, but not their full extent, are included.
Low-temperature specific heat of superconductors II: Progress in the new era
(2019-10-01)
Yang, H. D.
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Lin, J-Y
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Lin, J. G.
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Ho, J. C.
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交大名義發表
Beginning in the late 1980s, many unexpected superconductors have emerged. They raised not only the transition temperature limit but, just as importantly, the theoretical challenges beyond the BCS theory. Following the previous article on historical perspective of low-temperature specific heat of superconductors prior to 1986, we review briefly here some calorimetric studies on representative high-T-c and other novel superconductors discovered during the new era. Major emphasis is centered on special features of each set of temperature- and magnetic field-dependent specific heat data being fitted to select theoretical models. The models may involve multi-gap or a certain type of order-parameter symmetry.
Superconducting transition parameters in aluminum-lithium alloys (0-10 at.% Li)
(2007-05-01)
Ou, M. N.
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Yang, T. J.
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Chen, B. J.
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Chen, Y. Y.
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Ho, J. C.
The superconducting transition temperatures T-C of face-centered cubic Al1-x-Li-x alloys (x = 0-0.10) exhibit a minimum near x = 0.03 (3 at.% Li). The McMillan strong-coupling T, equation yields a similar trend of the electron-phonon coupling constant.. Meanwhile, the density of states at the Fermi level N(0) decreases monotonically with increasing x. It appears that T-C drops initially due to a reduced N(0), which is then overtaken by alloying-enhanced factors of phonon or electron-phonon interaction. (c) 2007 Elsevier Ltd. All rights reserved.