Role of Bond-Bond Interaction in the Extended Hubbard Chain

Abstract

Phase diagrams of the one-dimensional extended Hubbard model with a nearest neighbor interaction $V$ and site-off-diagonal (bond-charge $X$ and bond-bond $W$) interactions at half-filling are obtained numerically, using the level-crossing approach for finite-size clusters. This analysis is straightforward extension of the preceding work [cond-mat/9909277], where only the $X$ term is considered as a site-off-diagonal term. Similarly to the $X$ term, the $W$ term enlarges bond-charge-density-wave (BCDW) and bond-spin-density-wave (BSDW) phases for $W<0$ and $W>0$ cases, respectively. In the strong-coupling region, however, the $W$ term causes ferromagnetism for $W>0$, and shifts the boundary of the phase separation in the $U/t\ll-1$ region, which are different from the roles of the $X$ term. In addition, we discuss a parameter region where the BSDW state is the exact ground state, and show that the exactly solvable point appears just on the phase boundary between the BSDW and the ferromagnetic phases.Comment: 6 pages(JPSJ.sty), 3 figures(color EPS

Finite-temperature properties of the Hubbard chain with bond-charge interaction

“…Within this context, an increasing interest is nowadays devoted to the effects of unconventional correlation mechanisms, different from the usual charge-charge interaction terms between electrons on the same site ͑U͒ and on neighboring sites (V). In particular, models have been considered [1][2][3][4][5] which also account for the modification of the electron hopping motion by the presence of particles with opposite spins ͑correlated hopping͒; such kind of terms are also called bond-charge interactions, since they actually describe the interaction of charges located on bonds with those that are located on the lattice sites.…”

“…Within this context, an increasing interest is nowadays devoted to the effects of unconventional correlation mechanisms, different from the usual charge-charge interaction terms between electrons on the same site (U ) and on neighboring sites (V ). In particular, models have been considered [1][2][3][4][5] which also account for the modification of the electron hopping motion by the presence of particles with opposite spins (correlated hopping); such kind of terms are also called bond-charge interactions, since they actually describe the interaction of charges located on bonds with those that are located on the lattice sites. The first field of application of such kind of models in condensed matter was the description of π-electrons in conducting polymers such as polyacetylene (CH) x ; in particular it has been found [4] that, according to the strength of bond-charge coupling the dimerization of the polymeric chain can be enhanced or destroyed.…”

Level Spectroscopy: Physical Meaning and Application to the Magnetization Plateau Problems

“…21), 39), 40) The LS method has been applied not only to the quantum spin models but also to the lattice electron models, for instance, t − J and related models, 41) -43) and the extended Hubbard and related models. 43) - 49)…”

Phase separation in fermionic systems with particle–hole asymmetry

“…It was investigated by means of bosonization approach in [13] at half-filling for arbitrary (and weak) x and x ′ . Also, a particle-hole invariant subcase of H BC , which takes place at x ′ = 2x, has been previously discussed [14]. Recently, it has been proven [15], [16] that in 1D at halffilling H BC displays a rich phase diagram already at x ′ = 0, quite different from that of the Hubbard model, and from that derived in the weak coupling limit [13].…”