Related papers: Strongly anharmonic collective modes in a coupled …
We provide a comprehensive solution to the lattice dynamics problem in the two dimensional Holstein model at finite electron density and finite temperature. We work in the physically relevant adiabatic regime and vary the electron-phonon…
We study the finite-temperature transport of electrons coupled to anharmonic local phonons. Our focus is on the high-temperature incoherent regime, where controlled calculations are possible both for weak and strong electron--phonon…
We use a Langevin approach to treat the finite temperature dynamics of displacement variables in the half-filled spinless Holstein model. Working in the adiabatic regime we exploit the smallness of the adiabatic parameter to simplify the…
The physics of ferromagnetic doped manganites, such as \chem{La_{1-x}Ca_xMnO_3} with $x\approx0.2$--0.4, is reviewed. The concept of double exchange is discussed within the general framework of itinerant electron magnetism. The new feature…
The evolution of the properties of a finite density electronic system as the electron-phonon coupling is increased are investigated in the Holstein model using the Dynamical Mean-Field Theory (DMFT). We compare the spinless fermion case, in…
We develop a simple diagrammatic low-energy boson exchange strong-coupling model for an antiferromagnetically correlated polaronic metal. Important low-temperature features of such a model are (i) a large polaronic mass enhancement $Z$ and…
The interplay of the electron-phonon interaction and of the double and super exchange magnetic effects is analyzed in the $La_{1-x}Ca_xMnO_3$ perovskites with $0<x<0.5$. By using an analytical variational scheme that allows to treat the…
The cross over from low to high carrier densities in a many-polaron system is studied in the framework of the one-dimensional spinless Holstein model, using unbiased numerical methods. Combining a novel quantum Monte Carlo approach and…
We explore a novel coupling mechanism of electrons with the transverse optical (TO) phonon branch in a regime when the TO mode becomes highly anharmonic and drives the ferroelectric phase transition. We show that this anharmonicity, which…
An introduction is given to the many-body coherent potential approximation (CPA) for the double-exchange (DE) model and the Holstein-DE model, the latter including coupling of the electrons to local phonons as well as to local spins. It is…
Calculations of one-electron spectral functions, optical conductivity and spin-wave energy in the Holstein double-exchange model are made using the many-body coherent potential approximation. Satisfactory agreement is obtained with…
In metals in the vicinity of a polar transition, interactions between electrons and soft phonon modes remain to be determined. Here we explore the consequences of spin-orbit assisted electron-phonon coupling on the collective modes of such…
A comprehensive picture of polaron and bipolaron physics is essential to understand the optical absorption spectrum in many materials with electron-phonon interactions. In particular, the finite-temperature properties are of interest since…
The emergence of the bipolaronic phase and the formation of the heavy-electron state in the anharmonic Holstein model are investigated using the dynamical mean-field theory in combination with the exact diagonalization method. For a weak…
We present exact solutions, mainly analytical, for the two-site double-exchange-Holstein model, that allow us to draw a complete picture of the role of both phonon and spin quantum fluctuations in determining the short-range correlations in…
A new mechanism is proposed to explain the colossal magnetoresistance and related phenomena. Moving electrons accompanied by Jahn-Teller phonon and spin-wave clouds may form composite polarons in ferromagnetic narrow-band manganites. The…
We investigate the dynamical structure factor associated with lattice fluctuations in a model that approximates the manganites. It involves electrons strongly coupled to core spins, and to lattice distortions, in a weakly disordered…
While the vibrational thermodynamics of materials with small anharmonicity at low temperatures has been understood well based on the harmonic phonons approximation; at high temperatures, this understanding must accommodate how phonons…
We study the Hubbard-Holstein model using slave-boson mean-field and a variation al Lang-Firsov transformation. We identify weak and strong e-ph coupling solutions, whose stability depends both on the bare e-ph coupling and on the…
We investigate the interaction of strongly correlated electrons with phonons in the frame of the Hubbard-Holstein model. The electron-phonon interaction is considered to be strong and is an important parameter of the model besides the…