SUPERCONDUCTIVITY WITH SOFT LATTICE MODES IN LaBaCuO and YBaCuO

2001 ◽  
Vol 15 (32) ◽  
pp. 4145-4160 ◽  
Author(s):  
STEPHEN NETTEL
Keyword(s):  
Electron Correlation ◽  
Pair Correlation ◽  
Negative Energy ◽  
Variational Calculation ◽  
Phonon Interaction ◽  
Phonon Softening ◽  
Intermediate Coupling ◽  
Normal Coordinates ◽  
Electron Phonon Interaction ◽  
Lattice Modes

The canonical transformation employed in polaron theory at intermediate coupling is generalized to the electron phonon interaction of an entire band of electrons. Interelectron interactions result. The overall lattice-electron correlation is obtained with a variational calculation, balancing the extra elastic energy stored in the lattice against the negative energy arising from BCS pair correlation. The requisite phonon softening to attain any given value of Tc in metallic LaBaCuO and YBaCuO are estimated. The implicit fluctuations in the lattice normal coordinates are compared with results yielded by the EXAFS measurements of Oyanagi et al.

THE EFFECT OF STRONG ELECTRON-PHONON INTERACTIONS ON THE INFRARED REFLECTANCE IN HIGH-Tc SUPERCONDUCTORS

1991 ◽  
Vol 05 (20) ◽  
pp. 1361-1365 ◽  
Author(s):  
S. Y. TIAN ◽  
M. H. LI ◽  
Z. X. ZHAO
Keyword(s):  
High Temperature Superconductors ◽  
Peak Position ◽  
Superconducting Gap ◽  
High Tc Superconductors ◽  
Phonon Interaction ◽  
Phonon Softening ◽  
Strong Electron ◽  
High Tc ◽  
Electron Phonon Interaction ◽  
And Shifts

We show that the model of charge-transfer fluctuation with LO phonons can unify the interpretation of the infrared features and the phonon softening at about 55 meV measured by neutron scattering experiments in high temperature superconductors. Based upon this model we demonstrate that reflectivity ratio of superconducting state to normal state is strongly modified as a result of strong electron-phonon interaction which is different from Holstein mechanism. A broad peak in the ratio reflectivity develops around the peak position of different neutron phonon density of states. This peak becomes stronger and shifts to a higher frequency as the coupling increases at lower temperatures. This situation complicates the interpretation of the ratio reflectivity peak as the superconducting gap.

Charge density fluctuations and the softening of phonons in electron–phonon systems

1976 ◽  
Vol 54 (10) ◽  
pp. 1006-1010 ◽  
Author(s):  
Yasunari Kurihara
Keyword(s):  
Charge Density ◽  
Density Wave ◽  
Density Fluctuations ◽  
Electron Interaction ◽  
Periodic Lattice ◽  
Phonon Interaction ◽  
Phonon Softening ◽  
Wave State ◽  
Electron Phonon Interaction ◽  
Diagrammatic Method

The theory of charge–density fluctuations and phonon-softening is formulated exactly using the diagrammatic method for simple electron–phonon systems without many band effects and Umklapp processes. These electron–phonon systems are classified to three cases according to the strength of the electron–electron interaction and the electron–phonon interaction. The criteria for occurrence of the charge-density wave state and periodic lattice distortion are discussed in each case. They are given using the partial summation of diagrams. Here the phase transition is assumed to be of second order.

PHENOMENA IN RESONANT TUNNELING THROUGH DEGENERATED ENERGY STATES WITH ELECTRON CORRELATION

2007 ◽  
Vol 21 (11) ◽  
pp. 1827-1835 ◽  
Author(s):  
VLADIMIR N. ERMAKOV ◽  
SERGEI P. KRUCHININ ◽  
HIDENOBU HORI ◽  
AKIHIKO FUJIWARA
Keyword(s):  
Electron Correlation ◽  
Resonant Tunneling ◽  
High Performance ◽  
Coulomb Repulsion ◽  
Analysis Method ◽  
Phonon Interaction ◽  
Strong Electron ◽  
Electron Phonon Interaction ◽  
Wide Range ◽  
Good Agreement

We introduce a general analysis method, which allows us to simulate the operation of high-performance molecular nano-devices and to design the expected function of a wide range of devices in nano-scale size. The method is based on the use of a resonant tunneling phenomenon, admitting strong electron correlation in a quantum dot with degenerated states. Three examples of the application of this method are given: Coulomb repulsion, uncorrelated resonant tunneling, and electron-phonon interaction. It is shown that there is a good agreement with experimental data in all three cases.

Sign in / Sign up

Export Citation Format

Share Document