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Modeles de dimeres classiques et quantiques pour des systemes d'electrons correles bidimensionnels

Fabien Trousselet 1
1 FFC - Fermions Fortement Corrélés (LPT)
LPT - Laboratoire de Physique Théorique
Abstract : This thesis treats various topics about strongly correlated electronic systems in two spatial dimensions (compounds with geometrical frustration, resonating valence bond phases) described in terms of dimer models. A part of the thesis discusses classical dimer models, and especially an interacting dimer model on an anisotropic triangular lattice, presenting critical phases descrip- tible with help of conformal field theories ; based on these theories, the numerical analysis of this model allowed to characterize the conditions for the existence of criticality, and more generally the phase diagram in function of interaction parameters and of the lattice anisotropy. Another part treats a system of electrons on a two-dimensional version (checkerboard lattice) of the py- rochlore lattice, at commensurate particle filling. In a strong interacting limit, local constraints on charge repartition are those of dimer on the square lattice, thus an effective quantum dimer model is derivated. This model differs from the Rokhsar-Kivelson model (motivated by resona- ting valence bond phases in cuprates) by, here, an additional spin degree of freedom for each dimer. A study with exact diagonalisation, completed ba a variational approach and arguments from perturbation theory, allowed to identify an insulating crystal phase of resonating singlets ; an extension of this model to small but finite electron mobility was eventually considered with the aim to characterize the transition from this insulator to a metallic state when increasing the ratio of the electron mobility over interaction strength.
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Fabien Trousselet. Modeles de dimeres classiques et quantiques pour des systemes d'electrons correles bidimensionnels. Physique [physics]. Université Paul Sabatier - Toulouse III, 2009. Français. ⟨tel-00404146⟩

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