Berlin 2012 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 16: Correlated Electrons: Low-dimensional Systems - Models 2
TT 16.9: Talk
Tuesday, March 27, 2012, 11:45–12:00, H 0104
Valence bond crystal and possible analog of a supersolid in a t2g orbital model — •Fabien Trousselet1, Arnaud Ralko2, and Andrzej M. Oleś1,3 — 1Max Planck Institut für Festkörperforschung, Stuttgart, Germany — 2Institut Néel, Grenoble, France — 3Marian Smoluchowski Institute of Physics (Jagiellonian University), Kraków, Poland
We investigate an orbital model for localized t2g electrons on the triangular lattice, and interacting via exchange processes between nearest neighbors. The Hamiltonian interpolates between two limits where either superexchange or direct-exchange predominates; it is relevant to some titanate compounds (e.g. NaTiO2), in a situation where spins are polarized by e.g. a large magnetic field.
Within this frame, we analyze the ground state properties of the model, by exact diagonalizations and the use of effective Hamiltonians. When superexchange interactions dominate, they favor orbital singlets on nearest neighbor bonds, which results in a dimerized phase. We characterize this phase, with help of an effective quantum dimer model, as a valence bond crystal with a large unit cell. In the opposite regime of dominant direct-exchange, we find another exotic phase, which can be seen as an orbital analog of a supersolid, where long-ranged orbital order coexists with dynamics induced by perturbing kinetic terms.