Bond-order-wave phase and quantum phase transitions in the one-dimensional extended Hubbard model
Sandvik, Anders W.
Campbell, David K.
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Citation (published version)P Sengupta, AW Sandvik, DK Campbell. 2002. "Bond-order-wave phase and quantum phase transitions in the one-dimensional extended Hubbard model." PHYSICAL REVIEW B, Volume 65, Issue 15, pp. ? - ? (18). https://doi.org/10.1103/PhysRevB.65.155113
We use a stochastic series-expansion quantum Monte Carlo method to study the phase diagram of the one-dimensional extended Hubbard model at half-filling for small to intermediate values of the on-site U and nearest-neighbor V repulsions. We confirm the existence of a novel, long-range-ordered bond-order-wave (BOW) phase recently predicted by Nakamura [J. Phys. Soc. Jpn. 68, 3123 (1999)] in a small region of the parameter space between the familiar charge-density-wave (CDW) state for V≳U/2 and the state with dominant spin-density-wave (SDW) fluctuations for V≲U/2. We discuss the nature of the transitions among these states and evaluate some of the critical exponents. Further, we determine accurately the position of the multicritical point, (Um,Vm)=(4.7±0.1,2.51±0.04) (in energy units where the hopping integral is normalized to unity), above which the two continuous SDW-BOW-CDW transitions are replaced by one discontinuous (first-order) direct SDW-CDW transition. We also discuss the evolution of the CDW and BOW states upon hole doping. We find that in both cases the ground state is a Luther-Emery liquid, i.e., the spin gap remains but the charge gap existing at half-filling is immediately closed upon doping. The charge and bond-order correlations decay with distance r as r−ᴷρ, where Kρ is approximately 0.5 for the parameters we have considered. We also discuss advantages of using parallel tempering (or exchange Monte Carlo)—an extended ensemble method that we here combine with quantum Monte Carlo—in studies of quantum phase transitions.