Browsing by Author "Sheng, PJ"

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Inelastic electron dephasing times in CuxGe100-x alloys
(2000-05-01)
Lin, JJ
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Sheng, PJ
;
Hsu, SY
;
電子物理學系
;
物理研究所
We have studied the inelastic electron dephasing scattering times, tau(i). in disordered CuxGe100-x(35 less than or equal to x less than or equal to 60) alloys between I and 15 K. The values of tau(i)(-1) (similar to T-p), and especially the exponent of temperature p, are extracted from weak localization studies. We find that the value of p continuously decreases from similar to 3 to similar to 1 as x gradually decreases from 60 to 35. Our observation is understood in terms of a crossover of the inelastic electron dephasing in impure metals from e-Fh scattering to critical e-e scattering as the disorder greatly increases and the system moves significantly toward the mobility edge. (C) 2000 Elsevier Science B.V. All. rights reserved.
Quadratic temperature dependence of the electron-phonon scattering rate in disordered metals
(1999-08-01)
Hsu, SY
;
Sheng, PJ
;
Lin, JJ
;
電子物理學系
;
物理研究所
We have measured the electron-phonon scattering rates 1/tau(ep) from a weak-localization study of a series of high-resistivity tin-doped Ti73Al27 alloys. The resistivities of these alloys are essentially the same and are so high that the electron elastic mean free path I approaches the interatomic spacing, resulting in a very small value of q(ph) l approximate to 0.0056 T (q(ph) is the wave number of the thermal phonons, and T is the temperature). Based on as many as about 60 magnetoresistivity measurements between 2 and 22 K, we are able to determine the dependence of 1/tau(ep) on T to within a great degree of accuracy and find that 1/tau(ep) varies essentially with T-2 in the dirty limit (q(ph) l much less than 1). This observation is not understood in terms of the current theoretical concept of electron-phonon interaction in disordered metals. [S0163-1829(99)05030-4].
Spin-orbit scattering effect on electron-electron interactions in disordered metals
(2001-09-01)
Lin, JJ
;
Hsu, SY
;
Lue, JC
;
Sheng, PJ
;
電子物理學系
We have measured the low-temperature resistivities of a series of bulk crystalline disordered Ti73-xAl27Snx alloys (x less than or similar to 5) as well as the sheet resistances of a number of thin ferromagnetic Ni films (approximate to 120 Angstrom thick) sandwiching an ultrathin Ag or Au (less than or similar to5 Angstrom) layer. The level of impurities (concentration of Sn in the former ease, and thickness of Ag or Au in the latter case) is progressively increased in order to enhance the spin-orbit scattering in a controllable manner. The influence of the spin-orbit scattering on the electron-electron interaction effects is studied from the temperature dependence of resistivities (sheet resistance) at low temperatures. We find that the electron-electron interaction contribution to the resistivities (sheet resistances) increases slightly with increasing spin-orbit scattering. Our observation is discussed in terms of the current theoretical concept for the electron-electron interactions in disordered metals. (C) 2001 Elsevier Science Ltd. All rights reserved.