ELECTRICAL CONDUCTIVITY IN THE STRONG CORRELATION LIMIT OF THE TWO BAND EMERY MODEL

Kenn Kubo

B. M. Letfulov

Sorokov, Levitskii, O. R. Baran

Introduction Among pseudospin systems studied theoretically, a great attention is paid to Ising-type models, that is, to systems with the Hamiltonian containing only z-component of pseudospin. That is so due to relative simplicity with which approximate calculations for these models can be carried out and tested and possibility of their application to a wide class of real objects. Thus, the Blume-Emery-Griffiths model (BEG) corresponding to the Isingtype model with j = 2 (hereafter S z = \\Gammaj; \\Gammaj +2; : : : ; j \\Gamma 2; j) was proposed for the investigation of phase transitions (PT) in He 3 \\Gamma He 4 mixture [1]. A general form of the Ising-type model with j = 2 contains extra terms, as compared to the BEG model, like S z i (S z j<

Dieter Ihle, B. Lorenz

S. Fratini, FERDINANDO DE PASQUALE, Sergio Ciuchi

We apply the dynamical mean field theory to calculate the low-density limit of the small polaron optical conductivity in the Holstein model. Classical schemes of approximation are recovered in weak coupling and in the adiabatic and anti-adiabatic strong coupling limits. Such schemes are not suitable for the intermediate coupling regime, where our theory gives an anomalous behaviour of the spectral weight at low energy as the temperature decreases.

S.-J. Gu, J. Cao, S. Chen +2 more