TY - JOUR
T1 - Effect of doublon-holon binding on Mott transition-variational Monte Carlo study of two-dimensional Bose Hubbard models
AU - Yokoyama, Hisatoshi
AU - Miyagawa, Tomoaki
AU - Ogata, Masao
PY - 2011/8
Y1 - 2011/8
N2 - To understand the mechanism of Mott transitions in the case of no magnetic influence, superfluid-insulator (Mott) transitions in the S = 0 Bose Hubbard model at unit filling are studied on square and triangular lattices, using a variational Monte Carlo method. In trial many-body wave functions, we introduce various types of attractive correlation factors between a doubly occupied site (doublon, D) and an empty site (holon, H), which play a central role for Mott transitions, in addition to the onsite repulsive (Gutzwiller) factor. By optimizing distance-dependent parameters, we study various properties of this type of wave functions. With a hint from the Mott transition arising in a completely D-H bound state, we propose an improved picture of Mott transitions, by introducing two characteristic length scales, the D-H binding length ζdh and the minimum D-D exclusion length ζdd. Generally, a Mott transition occurs when ζdh becomes comparable to ζdd. In the conductive (superfluid) state, domains of D-H pairs overlap with each other (ζdh > ζdd); therefore, D and H can propagate independently as density carriers by successively exchanging partners. In contrast, intersite repulsive Jastrow (D-D and H-H) factors have little importance for the Mott transition.
AB - To understand the mechanism of Mott transitions in the case of no magnetic influence, superfluid-insulator (Mott) transitions in the S = 0 Bose Hubbard model at unit filling are studied on square and triangular lattices, using a variational Monte Carlo method. In trial many-body wave functions, we introduce various types of attractive correlation factors between a doubly occupied site (doublon, D) and an empty site (holon, H), which play a central role for Mott transitions, in addition to the onsite repulsive (Gutzwiller) factor. By optimizing distance-dependent parameters, we study various properties of this type of wave functions. With a hint from the Mott transition arising in a completely D-H bound state, we propose an improved picture of Mott transitions, by introducing two characteristic length scales, the D-H binding length ζdh and the minimum D-D exclusion length ζdd. Generally, a Mott transition occurs when ζdh becomes comparable to ζdd. In the conductive (superfluid) state, domains of D-H pairs overlap with each other (ζdh > ζdd); therefore, D and H can propagate independently as density carriers by successively exchanging partners. In contrast, intersite repulsive Jastrow (D-D and H-H) factors have little importance for the Mott transition.
KW - Bose Hubbard model
KW - Doublon-holon binding
KW - Insulator
KW - Mott transition
KW - Superfluid
KW - Two dimensions
KW - Variational Monte Carlo method
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U2 - 10.1143/JPSJ.80.084607
DO - 10.1143/JPSJ.80.084607
M3 - Article
AN - SCOPUS:80051598555
VL - 80
JO - Journal of the Physical Society of Japan
JF - Journal of the Physical Society of Japan
SN - 0031-9015
IS - 8
M1 - 084607
ER -