Browsing by Author "Zhong, YL"

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Anomalous temperature and disorder dependence of the electron-phonon scattering time in impure metals
(2003-05-01)
Lin, JJ
;
Zhong, YL
;
Kao, LY
;
Meikap, AK
;
物理研究所
We have measured the electron-phonon scattering time, tau(ep), in disordered metals at liquid-helium temperatures, using weak-localization method. The temperature and disorder dependence of tau(ep), is determined for AgPd and AuPd thick films, and V100-xAlx alloys. In all three cases, we find an anomalous temperature and disorder dependence of tau(ep)(-1) proportional to T(2)l where l is the electron elastic mean free path. This temperature and disorder behavior cannot be explained in terms of current theoretical concepts for the electron-phonon interaction in impure conductors. Current theory predicts a form of either tau(ep)(-1) proportional to T(4)l or tau(ep)(-1) proportional to T(2)l(-1) in the dirty limit, depending on the nature of the defects. (C) 2003 Elsevier Science B.V. All rights reserved.
Effect of annealing on electron dephasing in three-dimensional polycrystalline metals
(2002-03-01)
Lin, JJ
;
Zhong, YL
;
Li, TJ
;
電子物理學系
;
物理研究所
We have studied the effect of thermal annealing on electron dephasing times in three-dimensional polycrystalline metals. Measurements are performed on as-sputtered and annealed AuPd and Sb thick films, using the weak-localization method. In all samples, we find that possesses an extremely weak temperature dependence as T --> 0. Our results show that the effect of annealing is non-universal, and it depends strongly on the amount of disorder quenched in the microstructures during deposition. The observed saturation behavior of cannot be easily explained by magnetic scattering. We suggest that the issue of saturation can be better addressed in three-dimensional, rather than lower-dimensional, structures.
Effect of microstructure on the electron-phonon interaction in the disordered metals Pd60Ag40
(2002-10-01)
Zhong, YL
;
Lin, JJ
;
Kao, LY
;
物理研究所
;
Institute of Physics
Using the weak-localization method, we have measured the electron-phonon scattering times tau(ep) in Pd60Ag40 thick films prepared by dc- and rf-sputtering deposition techniques. In both series of samples, we find an anomalous 1/tau(ep)proportional toT(2)l temperature and disorder dependence, where l is the electron elastic mean free path. This anomalous behavior cannot be explained in terms of the current concepts for the electron-phonon interaction in impure conductors. Our result also reveals that the strength of the electron-phonon coupling is much stronger in the dc- than rf-sputtered films, suggesting that the electron-phonon interaction is not only sensitive to the total level of disorder, but is also sensitive to the microscopic quality of the disorder.
Electron-electron scattering times in low-diffusivity thick RuO2 and IrO2 films
(1999-01-01)
Lin, JJ
;
Xu, W
;
Zhong, YL
;
Huang, JH
;
Huang, YS
We have systematically measured the electron dephasing scattering times from a three-dimensional weak-localization study of low-diffusivity thick RuO2 and IrO2 films. We find that the inelastic electron scattering rate 1/tau(in) varies essentially Linearly with the temperature and there is essentially no dependence of 1/tau(in) on the electron elastic mean free path. This observation is understood in terms of the current theoretical concept for electron-electron scattering in strongly disordered bulk conductors. [S0163-1829(99)02601-6].
Electronic transport in insulating AlPdRe quasicrystals
(2004-02-18)
Rosenbaum, R
;
Murphy, T
;
Brandt, B
;
Wang, CR
;
Zhong, YL
Resistivity and magnetoresistance measurements have been performed on insulating icosahedral AlPdRe quasicrystal (QC) bar samples. At temperatures in the range 300 K greater than or equal to T greater than or equal to 50 K, the resistivities follow a simple inverse temperature law: rho(T) rho(0)/T(1.0+/-0.1). Below 1 K, the resistivity of a weakly insulating sample exhibited a simple inverse temperature law where rho(T) = rho0/T-0.33 and not an activated variable-range hopping (VRH) law. Strongly insulating samples exhibit saturation of their resistivities to finite values as T --> 0 K. These saturation resistivity values are believed to arise from the presence of a second metallic phase located within the quasicrystal's structure. By extrapolating the measured resistivities at 22 mK to absolute zero, the saturation conductivity values were estimated at T = 0 K and subtracted from the conductivity data points. These 'corrected' data, corresponding only to the QC phase, were found to follow activated VRH laws, having hopping exponents y that vary in the range 0.18 less than or equal to y less than or equal to 0.43. The activated VRH behaviours are observed only below 1 K. The magnetoresistances (MRs) of these samples are also anomalous. The MRs can be explained by including contributions from both the saturation conductivity values and from the QC MR ratios, estimated using the wavefunction shrinkage model.