Penc Karló (Wigner SZFI): The ground states of two-dimensional SU(N) Heisenberg models

Friday 28 Feb 2020, 14:00 → 16:00 Europe/Budapest

Tanacsterem

The Mott insulating states realized in transition metal compounds with spin and orbital
degrees of freedom and by ultracold fermionic atoms in optical lattices are described by SU(N) symmetric
Heisenberg models, where the states of the N-dimensional local Hilbert
space are exchanged on the neighboring sites.The quantum fluctuations in these models are enhanced compared to usual magnetic system, and depending on the lattice geometry,  ordered as well as disordered phases of different kind can be realized. I will start with the simplest example for an ordered state, the SU(3) model on the triangular lattice. The SU(3) Heisenberg model on square lattice will serve as a next example: the mean field ground state is macroscopically degenerate, and quantum fluctuations select the ordered ground state via the order by disorder mechanism. Considering larger N, the SU(4) Heisenberg model undergoes a spontaneous dimerization on the square lattice, while on the honeycomb lattice it is a quantum liquid with algebraic spin correlation. Finally, in some cases a chiral phase is realized. I will discuss the general principles behind the selection of different ground states.

 

SUN_Wigner_2020_02_28.pdf