7 research outputs found
Effect of screening of the electron-phonon interaction on the temperature of Bose-Einstein condensation of intersite bipolarons
Here we consider an interacting electron-phonon system within the framework
of extended Holstein-Hubbard model at strong enough electron-phonon interaction
limit in which (bi)polarons are the essential quasiparticles of the system. It
is assumed that the electron-phonon interaction is screened and its potential
has Yukawa-type analytical form. An effect of screening of the electron-phonon
interaction on the temperature of Bose-Einstein condensation of the intersite
bipolarons is studied for the first time. It is revealed that the temperature
of Bose-Einstein condensation of intersite bipolarons is higher in the system
with the more screened electron-phonon interaction.Comment: 6 pages, 4 figure
The Jahn-Teller Polaron in Comparison with the Holstein Polaron
Based on an exact expression for the self-energy of the Jahn-Teller polaron,
we find that symmetry of pseudospin rotation makes the vertex correction much
less effective than that for the Holstein polaron. This ineffectiveness brings
about a smaller effective mass m^* and a quantitatively differenent
large-to-small polaron crossover, as examined by exact diagonalization in a
two-site system. In the strong-coupling and antiadiabatic region, a rigorous
analytic expression is found for m^*