University of Minnesota
School of Physics & Astronomy

Physics and Astronomy Calendar

Friday, February 13th 2015
11:30 am:
Speaker: Maciej Koch-Janusz, Weizmann Institute of Science
Subject: Two-dimensional Valence Bond Solid (AKLT) states from t_{2g} electrons

Two-dimensional AKLT model on a honeycomb lattice has been shown to be a universal resource for quantum computation. In this valence bond solid, however, the spin interactions involve higher powers of the Heisenberg coupling (S_i *S_j)^n, making these states seemingly unrealistic on bipartite lattices,
where one expects a simple antiferromagnetic order. We show that those interactions can be generated by orbital physics in multiorbital Mott insulators. We focus on t_{2g} electrons on the honeycomb lattice and propose a physical realization of the spin-3/2 AKLT state. We find a phase transition from the AKLT to the Neel state on increasing Hund's rule coupling, which is confirmed by density matrix renormalization group (DMRG) simulations. An experimental signature of the AKLT state consists of protected, free spins-1/2 on lattice vacancies, which may be detected in the spin susceptibility.

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