Finite frequency ultrasonic attenuation in an anisotropic superconductor

1978 ◽  
Vol 56 (10) ◽  
pp. 1395-1398
Author(s):  
K. M. Hong ◽  
J. P. Carbotte
Keyword(s):  
Fermi Surface ◽  
Energy Gap ◽  
Ultrasonic Attenuation ◽  
Pair Breaking ◽  
Finite Frequency ◽  
Finite Amount ◽  
Anisotropic Superconductor ◽  
Gap Values

The ultrasonic attenuation of an isotropic superconductor shows a finite jump at a frequency of twice the energy gap because of the onset of pair breaking. For an anisotropic superconductor it is shown that the rise in attenuation proceeds in steps when there exist regions on the Fermi surface with distinct gap values separated by a finite amount.

Ultrasonic attenuation at 500 kHz in superconducting tin

1969 ◽  
Vol 309 (1497) ◽  
pp. 259-280 ◽  
Keyword(s):  
Fermi Surface ◽  
Free Path ◽  
Phonon Scattering ◽  
Ultrasonic Attenuation ◽  
Mean Free Path ◽  
Attenuation Curve ◽  
Anisotropic Superconductor ◽  
Gap Anisotropy ◽  
Heavily Doped ◽  
Good Agreement

The temperature dependence of the longitudinal ultrasonic attenuation in single crystals of white tin has been measured by a resonance technique at a frequency of 500 kHz between 1 and 4.2 °K, for propagation along (100) and (001). The resistance ratio of the samples varied from 800 to 30000 and in all cases the electronic mean free path is smaller than the ultrasonic wavelength. No difference is found between propagation along (100) and (001) in the most heavily doped samples, in contrast to the suggestion of Kadanoff & Pippard, although in this case the normalized attenuation curve lies above the form found by Bardeen, Cooper & Schrieffer (B.C.S.). A systematic decrease of attenuation with increasing purity is found, so that in the most pure samples the curve lies well below the B.C.S. form. This effect is more marked for (001) propagation. A simple model is used to calculate the details of elastic scattering in the anisotropic superconductor, and it is shown that scattering across the Fermi surface can account for the lack of any orientational differences. The free path of the excitations is modified by the anisotropy: this brings the theory into very good agreement with the present results, and also increases the theoretical anisotropy of thermal conductivity in tin so as to agree with experiment. Phonon scattering across the Fermi surface is shown to account for the variation of attenuation with purity; the anisotropy of this effect is consistent with the gap anisotropy.

Ultrasonic attenuation in white tin crystals

1967 ◽  
Vol 297 (1450) ◽  
pp. 408-423 ◽  
Keyword(s):  
Fermi Surface ◽  
Energy Gap ◽  
Ultrasonic Attenuation ◽  
Propagation Direction ◽  
Frequency Range ◽  
Weighted Averages ◽  
Conduction Electrons ◽  
Energy Gaps ◽  
Surface Measurements ◽  
Gap Parameter

A detailed study of the temperature dependence of the longitudinal ultrasonic attenuation in single crystals of white tin is presented. Measurements have been made at temperatures from 0⋅8 to 4⋅2°K on pure and impure samples in the frequency range 40 to 290 Mc/s, corresponding to ql e values 0⋅45 to 90, where q is the ultrasonic wave vector and l e the free path of the conduction electrons. For high ql e an energy gap parameter A = 2∆(0)/ kT c is measured as an average over a narrow effective zone of the Fermi surface. For propagation along <001>, A = 3⋅15 ± 0⋅04; along <310>, A = 4⋅24 ± 0⋅04; along <100>, A = 3⋅55 ± 0⋅04; along <110>, A = 3⋅84 ± 0⋅07. The results are interpreted by assigning different energy gaps to different zones of the Fermi surface. Measurements with ql e ~ 0⋅5 yield A = 3⋅47 ± 0⋅06, independent of the propagation direction, showing that the effective zone extends to the whole Fermi surface for such low ql e . A simple two-gap model of a superconductor is used to show that the gaps measured here are weighted averages over an effective zone, and not minima. At lower temperatures the attenuation is shown to depend on the minimum gap, in agreement with the analysis of Privorotskii, but to be negligibly small for tin.

T(Z) diagram and optical energy gap values of (AgIn)2(1–z)(CdIn2)zTe4 alloys

1994 ◽  
Vol 144 (2) ◽  
pp. 311-316 ◽  
Author(s):  
R. Cadenas ◽  
M. Quintero ◽  
J. C. Woolley
Keyword(s):  
Energy Gap ◽  
Optical Energy Gap ◽  
Optical Energy ◽  
Gap Values

Bandstruktur der linearen Polyacene

1975 ◽  
Vol 30 (10) ◽  
pp. 1308-1310 ◽  
Author(s):  
N. N. Tyutyulkov ◽  
O. E. Polansky ◽  
J. Fabian
Keyword(s):  
Spectroscopic Data ◽  
Energy Gap ◽  
Molecular Geometry ◽  
Electronic Correlation ◽  
Dependent Factor ◽  
Good Agreement ◽  
Gap Values

Abstract For infinite polyacenes the energy gap (ΔE∞) is given by ΔE = , where Δcorr is a factor determined by the electronic correlation and Δgeom is a molecular geometry dependent factor. We find in the selected case Δcorr>Δgeom .The energy gap values calculated with this formula are in good agreement with the values calculated from the spectroscopic data of polyacenes (0.8-0.9 eV).

scholarly journals Two-Fermi-Surface Superconducting State and a Nodald-Wave Energy Gap of the Electron-DopedSm1.85Ce0.15CuO4−δCuprate Superconductor

2011 ◽  
Vol 106 (19) ◽  
Author(s):  
A. F. Santander-Syro ◽  
M. Ikeda ◽  
T. Yoshida ◽  
A. Fujimori ◽  
K. Ishizaka ◽  
...  
Keyword(s):  
Fermi Surface ◽  
Wave Energy ◽  
Superconducting State ◽  
Energy Gap

(Culn)J.(Agln)!/Mn2jTe:, Alloys: T(z) Phase Diagram and Optical Energy Gap Values

1989 ◽  
pp. 157-165
Author(s):  
M. Quintero ◽  
R . Tovar ◽  
M. Dhksi ◽  
J. Woolley
Keyword(s):  
Phase Diagram ◽  
Energy Gap ◽  
Optical Energy Gap ◽  
Optical Energy ◽  
Gap Values

Temperature Variation of Energy Gap Values in CuGa(Se1-xSx)2

1980 ◽  
Vol 19 (S3) ◽  
pp. 123 ◽  
Author(s):  
Gerald Goodchild ◽  
John C. Woolley ◽  
Jesus Gonzales
Keyword(s):  
Temperature Variation ◽  
Energy Gap ◽  
Gap Values

T(z) Diagram and Optical Energy Gap Values of Zn1-zMnzGa2Se4 Alloys

1995 ◽  
Vol 115 (2) ◽  
pp. 416-419 ◽  
Author(s):  
M. Morocoima ◽  
M. Quintero ◽  
J.C. Woolley
Keyword(s):  
Energy Gap ◽  
Optical Energy Gap ◽  
Optical Energy ◽  
Gap Values
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