Temperature dependence of electronic transitions in MgO, α-Al2O3, and α-SiO2: Final-state effects on phonon coupling

1992 ◽  
Vol 45 (7) ◽  
pp. 3882-3885 ◽  
Author(s):  
W. L. O’Brien ◽  
J. Jia ◽  
Q-Y. Dong ◽  
T. A. Callcott ◽  
D. R. Mueller ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Electronic Transitions ◽  
Phonon Coupling ◽  
Final State ◽  
Α Al2o3

Theory of Ferroelectric Phase Transitions in Pure and Mixed Perovskites.

2002 ◽  
Vol 718 ◽  
Author(s):  
Yizhak Yacoby ◽  
Yakov Girshberg
Keyword(s):  
Temperature Dependence ◽  
Ferroelectric Phase ◽  
Paraelectric Phase ◽  
Soft Mode ◽  
Critical Concentration ◽  
Comprehensive Model ◽  
Coupling Constant ◽  
Phonon Coupling ◽  
Ferroelectric Phase Transitions ◽  
Basic Experimental Data

AbstractWe present a comprehensive model of ferroelectricity in oxygen perovskite crystals that account quantitatively for both displacive like and order-disorder like properties. The model assumes that in the paraelectric phase, the system has a soft mode, interacting with spontaneous disordered off-center displacements. The resulting theory is shown to quantitatively explain the properties of two representative perovskites: KNbO3 and PbTiO3. We have further extended this theory to explain the properties of mixed incipient ferroelectrics with small concentrations of ferroelectricity inducing ions such as KTa1-xNbxO3. The model quantitatively reproduces the basic experimental data in the quantum regime: the temperature dependence of the inverse dielectric function, the impurity and temperature dependence of the renormalized soft mode vibrational frequency and the impurity concentration dependence of the transition temperature Tc. In particular we show that, the critical concentration for Tc=0 is determined by the ion tunneling frequency, the bare soft mode parameters and the pseudospin - phonon coupling constant.

scholarly journals The effect of strong electron-rattling phonon coupling on some superconducting properties

2019 ◽  
Vol 97 (5) ◽  
pp. 472-476
Author(s):  
Samin Tajik ◽  
Božidar Mitrović ◽  
Frank Marsiglio
Keyword(s):  
Temperature Dependence ◽  
Coupling Parameter ◽  
Nmr Relaxation ◽  
Superconducting Gap ◽  
Phonon Coupling ◽  
Phonon Modes ◽  
Strong Electron ◽  
Particle Decay ◽  
Electron Phonon Coupling ◽  
The One

Using the Eliashberg theory of superconductivity we have examined several properties of a model in which electrons are coupled only to rattling phonon modes represented by a sharp peak in the electron–phonon coupling function. Our choice of parameters was guided by experiments on β-pyrochlore oxide superconductor KOs2Os6. We have calculated the temperature dependence of the superconducting gap edge; the quasi-particle decay rate; the NMR relaxation rate assuming that the coupling between the nuclear spins and the conduction electrons is via a contact hyperfine interaction, which would be appropriate for the O-site in KOs2Os6; and the microwave conductivity. We examined the limit of very strong coupling by considering three values of the electron–phonon coupling parameter λ = 2.38, 3, and 5 and did not assume that the rattler frequency Ω0 is temperature dependent in the superconducting state. We obtained a very unusual temperature dependence of the superconducting gap edge Δ(T), very much like the one extracted from photoemission experiments on KOs2O6.

Das Temperaturverhalten der Phosphoreszenz und Fluoreszenz von K3CrF6 / The Temperature Dependence of Phosphorescence and Fluorescence in K3CrF6

1973 ◽  
Vol 28 (7) ◽  
pp. 1131-1135
Author(s):  
E. Koglin
Keyword(s):  
Experimental Data ◽  
Temperature Dependence ◽  
Crystal Field ◽  
Fluorescence Emission ◽  
Electronic Transitions ◽  
Luminescence Spectra ◽  
Site Symmetry ◽  
Energy Eigenvalues ◽  
Crystal Field Parameters ◽  
Fluorescence And Phosphorescence

The luminescence behaviour of crystalline K3CrF6 is measured in the temperature range from 100 °K to 4.2 °K. The complex shows a very strong, broad fluorescence emission at temperatures lower than 20 °K. additionally also the phosphorescence transition can be observed. At temperatures higher than 20 °K only fluorescence is measured. The 2E→4A2-transition does not split suggesting Oh-site symmetry.Excitation- and luminescence spectra at 4.2 °K are the basis for a calculation of the energy eigenvalues. The crystal field parameters are fitted by the experimental data. The vibrational sidebands of the electronic transitions 2E - 4A2 an 4T24A2 are compared with Raman- and IRresults. From the temperature dependence and measured vibrational frequencies the zero phonon transitions of fluorescence and phosphorescence can be found

The temperature dependence of vibronic lineshapes: Linear electron-phonon coupling

2014 ◽  
Vol 141 (15) ◽  
pp. 154110 ◽  
Author(s):  
Claudia Roos ◽  
Andreas Köhn ◽  
Jürgen Gauss ◽  
Gregor Diezemann
Keyword(s):  
Temperature Dependence ◽  
Linear Electron ◽  
Phonon Coupling ◽  
Electron Phonon Coupling

Temperature dependence of the Raman lines of α-Al2O3

1968 ◽  
Vol 6 (6) ◽  
pp. 343-346 ◽  
Author(s):  
M. Ashkin ◽  
J.H. Parker ◽  
D.W. Feldman
Keyword(s):  
Temperature Dependence ◽  
Α Al2o3
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