ISSN:
0392-6737
Schlagwort(e):
Phonons in crystal lattices
;
Polarons and electron-phonon interactions
;
Theories and models of superconducting state
;
Nonclassical field states
;
squeezed, antibunched, and sub-Poissonian states
;
operational definitions of the phase of the field
;
phase measurements
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Physik
Notizen:
Summary In the present work we have applied the correlated squeezed-state approach to investigate the ground state of the extended Hubbard model which is coupled to local Holstein phonons. Our study begins with decoupling the electron and phonon subsystems approximately by introducing a variational correlated squeezed-state ansatz for the phonons. Then assuming the renormalized intersite electron correlation of the effective electronic Hamiltonian to be attractive and the renormalized on-site correlation repulsive, we have applied the generalized Hartree-Fock approximation to obtain the ground state of the system, which is a superconducting state with intersite pairing. With optimal values of the variational parameters the correlated squeezed-state approach will by construction yield a ground-state energy lower than those obtained in previous studies. This means that our variational ansatz is more stable as the ground state of the system. Furthermore, our variational study shows that in the correlated squeezed state the polaronic reduction effect of phonons is much more alleviated, and thus the mass enhancement inherent to the polaron effect is noticeably weakened. This weakening of the reduction effect should, in turn, significantly affect other physical properties of the system.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF02459075
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