Doctoral dissertation
Phase separation in a 2D charged system
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Abstract
The main purpose of this thesis is to describe the inhomogeneous phase of a layered
system. The phase is the result of the competition between attractive interactions and
the long range Coulomb repulsive force (LRCF). In order to achieve this, two different
strategies are applied. The first is within the scheme of the Landau theory of phase
transitions and the second is based on Monte Carlo simulations of a lattice gas model.
An important feature addressed in the first approach is the coupling between the charge
density and the order parameter in the presence of LRCF. For this purpose two universal
classes of frustrated phase transitions were studied with different type of couplings.
Although in the Landau treatment it is not possible to track the microscopic origin of
the coupling with the charges, it is in the second approach where it is proposed that
the coupling to the order parameter is realized throughout a Jahn-Teller mechanism.
Hence, the inhomogeneities arising in the lattice gas model are identified as a result of
the competition between short range anisotropic attractions between JT-polarons and
the long range repulsion of these charged objects. Subsequently, throughout Monte Carlo
simulations, electric transport properties of the systems with such type of coupling are
presented.