El 05 de diciembre 2017, Oscar Nájera, miembro de AMARUN, defendió su tesis doctoral (Ph.D.) sobre el tema:

"Study of the dimer Hubbard Model within Dynamical Mean Field Theory and its application to VO2"

en la universidad de Paris-Saclay, Francia. 

Este trabajo de investigación fue realizado bajo al dirección del profesor Marcelo Rozenberg.

Resumen: We study in detail the solution of a basic strongly correlated model, namely, the dimer Hubbard model. This model is the simplest realization of a cluster DMFT problem. We provide a detailed description of the solutions in the “coexistent region” where two (meta)stable states of the DMFT equations are found, one a metal and the other an insulator. Moreover, we describe in detail how these states break down at their respective critical lines. We clarify the key role played by the intra-dimer correlation, which here acts in addition to the onsite Coulomb correlations. We review the important issue of the Mott-Peierls insulator crossover where we char- acterize a variety of physical regimes. In a subtle change in the electronic structure the Hubbard bands evolve from purely incoherent (Mott) to purely coherent (Peierls) through a state with unexpected mixed character. We find a singlet pairing temperature T∗ below which the localized electrons at each atomic site can bind into a singlet and quench their entropy, this uncovers a new paradigm of a para-magnetic Mott insulator. Finally, we discuss the relevance of our results for the interpretation of the recently discovered metastable phases of VO2 in various experimental studies. We present a variety of arguments that allow us to advance the conclusion that the long-lived (meta- stable) metallic phase, induced in pump-probe experiments, and the thermally activated M1 meta-stable metallic state in nano-domains are the same. In fact, they may all be qualitatively described by the dimerized correlated metal state of our model.

El documento de la tesis puede descargarse aqui.


12 Oscar Najera1 

12 Oscar Najera2