ZhETF, Vol. 148,
p. 549 (September 2015)
(English translation - JETP,
Vol. 121, No. 3,
available online at www.springer.com
PSEUDOSPIN S=1 FORMALISM AND SKYRMION-LIKE EXCITATIONS IN THE THREE-BODY CONSTRAINED EXTENDED BOSE-HUBBARD MODEL
Received: February 16, 2015
We discuss the most prominent and intensively studied S=1 pseudospin formalism for the extended boson Hubbard model (EBHM) with the on-site Hilbert space truncated to the three lowest occupation states n=0, 1, 2. The EBHM Hamiltonian is a paradigmatic model for the highly topical field of ultracold gases in optical lattices. The generalized non-Heisenberg effective pseudospin Hamiltonian does provide a deep link with a boson system and a physically clear description of ``the myriad of phases'', from uniform Mott insulating phases and density waves to two types of superfluids and supersolids. We argue that the 2D pseudospin system is prone to a topological phase separation and focus on several types of unconventional skyrmion-like topological structures in 2D boson systems, which have not been analyzed until now. The structures are characterized by a complicated interplay of insulating and two superfluid phases with a single-boson and two-boson condensation, respectively.