[PAST EVENT] Condense Matter Seminar
Strongly correlated systems provide a fertile ground for discovering exotic states of matter, for example, those with topologically non-trivial properties. Among these are frustrated magnets, where the lattice geometry prevents spins from ordering even at very low temperatures, thereby leading to "spin liquid" phases. Since their excitations involve quasiparticles with "fractional" anyonic statistics which are potentially useful for topological quantum computation, spin liquids have generated a lot of research activity on both theoretical and experimental fronts. The findings have also highlighted the need for accurate advanced numerical techniques to understand the quantum many body problem.
I will present two of our theoretical works in this area, both focusing on the kagome geometry which has near-ideal realizations in several materials. First, I present a study of the spin-1 Heisenberg antiferromagnet, where contrary to previous theoretical proposals, our calculations indicate that the ground state is a valence bond (simplex) solid with a spin gap that is consistent with experimental findings. In the second part, I consider the spin-1/2 XXZ model in a magnetic field, equivalent to a hard-core bosonic problem with density-density interactions at finite filling fraction. Motivated by previous field theoretical studies, I focus my attention to understanding the XY limit for the 2/3 magnetization plateau (i.e. 1/6 filling of bosons). We perform exact computations to search for the predicted "chiral spin liquid" and based on energetics and the determination of minimally entangled states and the associated modular matrices, provide evidence for this phase.