Regensburg 2013 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 38: Correlated Electrons: Metal-Insulator Transition 1

TT 38.9: Vortrag

Mittwoch, 13. März 2013, 11:45–12:00, H20

Effective singlet dynamics in Mott phases of two-dimensional Hubbard models — •Dominik Ixert and Kai Phillip Schmidt — Lehrstuhl für Theoretische Physik I, TU Dortmund, Germany

The Hubbard model is one of the paradigm models for the description of strongly correlated electron systems. In this work we focus on the intermediate-coupling regime inside the Mott insulating phase of single-band Hubbard models at zero temperature and at half filling. Recently, several works found indications for exotic spin-liquid phases close to the metal-insulator transition. While the situation on frustrated lattices like the triangular lattice concerning the existence of such interesting intermediate phases seems to be rather settled, the situation on unfrustrated lattices like the honeycomb lattice or the π-flux square lattice is currently under debate. In all these cases the Mott phase displays a long-ranged ordered antiferromagnet at strong couplings. Here our main focus is a class of two-dimensional systems for which the translational symmetry of the underlying square lattice is broken explicitly and the systems therefore realize a valence bond crystal at strong coupling. Consequently, one expects that the low-energy physics of the full Mott phase is contained in the singlet sector. For such systems we derive effective low-energy spin models using graph-based continuous unitary transformations (gCUTs). The effective spin models are then analyzed in the singlet sector by embedding the graphs within the dimer covering space on larger clusters to describe the singlet dynamics of the hubbard model.