Off-site Cooper pairing in strong electron-phonon interacting systems
We have developed a new variational treatment to deal with the superconductivity properties of systems with strong electron-phonon interactions by introducing a ''squeeze'' transformation for phonon operators. It is shown that as long as the renormalized intersite electron correlation is attractive, a new type of Cooper pairing occurs whether the renormalized on-site electron correlation is repulsive or atttractive. The transformed electron-phonon interaction gives rise to the squeezed polarons which are, in general, different from the ordinary polarons. We have found from this theory that: (1) the squeezed polaronic state corresponds to a stable minimum of the total energy; (2) the effective mass of the squeezed polaron is much smaller than that of ordinary polarons; (3) both the gap equation and the expression for the critical temperature T/sub c/ in squeezed polaronic states are different from those in ordinary polaronic states as well as from those in BCS theory; and (4) high T/sub c/ is obtained for simple cubic and body centered cubic lattice structures with the electron concentration n = 1.
- Research Organization:
- Department of Physics and Astronomy, State University of New York at Buffalo, Amherst, New York 14260
- OSTI ID:
- 6737698
- Journal Information:
- J. Appl. Phys.; (United States), Vol. 64:10
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
SUPERCONDUCTORS
ELECTRON-PHONON COUPLING
BCC LATTICES
BCS THEORY
COOPER PAIRS
CUBIC LATTICES
ISOTROPY
LOW TEMPERATURE
PHONONS
POLARONS
QUANTUM OPERATORS
THREE-DIMENSIONAL CALCULATIONS
TRANSITION TEMPERATURE
VARIATIONAL METHODS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
MATHEMATICAL OPERATORS
PHYSICAL PROPERTIES
QUASI PARTICLES
THERMODYNAMIC PROPERTIES
656100* - Condensed Matter Physics- Superconductivity