Speaker: Yasuyuki Kato, Los Alamos National Laboratory
Abstract: Spinel group comprise corner sharing tetrahedra and constitute paradigmatic examples of geometrically frustrated lattices. The spinel compound, ZnV2O4, is a Mott insulator with a rather small charge gap that undergoes a structural cubic to tetragonal transition at T=50(K). A magnetic transition at a lower temperature of T=40(K) has also been reported for this compound. The magnetic ordering corresponds to up-up-down-down spin configurations for chains oriented along the yz and zx directions. The origin of this magnetic ordering and the lack of orbital ordering in this material has been an open problem for several decades. The main obstacle was the lack of controlled and unbiased approaches for solving the correlated and frustrated model. I will introduce a novel quantum Monte Carlo method that can simulate the three-band Hubbard model relevant for these materials without generating any serious problem. We will see that this unbiased approach not only explains the observed magnetic ordering but also the lack of orbital ordering.