1. Magnetic phase diagram and quantum phase transitions in a two-species boson model
- Author
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K. I. Kugel, N. M. Chtchelkatchev, A. V. Mikheyenkov, and A. M. Belemuk
- Subjects
Quantum phase transition ,Phase transition ,FOS: Physical sciences ,Inverse ,02 engineering and technology ,Flory–Huggins solution theory ,01 natural sciences ,Condensed Matter - Strongly Correlated Electrons ,symbols.namesake ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,Antiferromagnetism ,010306 general physics ,Boson ,Condensed Matter::Quantum Gases ,Physics ,Condensed Matter - Mesoscale and Nanoscale Physics ,Strongly Correlated Electrons (cond-mat.str-el) ,Condensed matter physics ,021001 nanoscience & nanotechnology ,Quantum Gases (cond-mat.quant-gas) ,symbols ,Condensed Matter::Strongly Correlated Electrons ,Condensed Matter - Quantum Gases ,0210 nano-technology ,Ground state ,Hamiltonian (quantum mechanics) - Abstract
We analyze the possible types of ordering in a boson--fermion model. The Hamiltonian is inherently related to the Bose--Hubbard model for vector two-species bosons in optical lattices. We show that such model can be reduced to the Kugel--Khomskii type spin--pseudospin model, but in contrast to the usual version of the latter model, we are dealing here with the case of spin $S=1$ and pseudospin $1/2$. We show that the interplay of spin and pseudospin degrees of freedom leads to a rather nontrivial magnetic phase diagram including the spin-nematic configurations. Tuning the spin-channel interaction parameter $U_s$ gives rise to quantum phase transitions. We find that the ground state of the system always has the pseudospin domain structure. On the other hand, the sign change of $U_s$ switches the spin arrangement of the ground state within domains from ferro- to aniferromagnetic one. Finally, we revisit the spin (pseudospin)-1/2 Kugel--Khomskii model and see the inverse picture of phase transitions., Comment: 8 pages, 9 figures (in press), Phys. Rev. B, 2017
- Published
- 2017