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Applying the bosonization and renormalization group techniques, we study a generalized Hubbard chain incorporating extra off-diagonal hopping processes in the weak regime, and determine rich ground-state phase diagrams. At half filling, in addition to the insulating phases (HI, MI and DI), there exist the superconducting phases (LE and LL). The off-diagonal hopping accounts for the occurrence of insulator-superconductor transition. Away from half filling, the transition from the LL to LE phase takes place, and the insulating phases disappear. The result provides an insignificant insight into unconventional scenarios for Cooper pairing and insulator-superconductor transition. [ABSTRACT FROM AUTHOR]

We study a one-dimensional anisotropic extended Hubbard model, where the inter-site density ( V ) and exchange ( J ) interactions are spin-dependent. Use of bosonization and renormalization helps investigate phase diagram. At half filling, the ground state characterizes insulating phases. The spin-dependent repulsion leads to a bond-spin-density-wave (BSDW) phase. The antiferromagnetic exchange enhances the bond-order-wave (BOW) phase while weakens the charge-density-wave (CDW) phase. When J > 4 V , the BSDW and CDW phases disappear. Away from half filling, the ground state exhibits superconducting behavior. The anisotropic interactions have an important effect on the phase structures. [ABSTRACT FROM AUTHOR]

By introducing a modulation parameter ( ξ ), we study the one-dimensional correlated system with modulated hopping, on-site ( U ) and nearest-neighbor ( V ) repulsions in the weak-coupling regime. The induced three-body attraction changes topology of the conventional phase diagram. Besides the usual CDW and SDW phases, a BSDW phase exists for | U − 2 V | < 8 t ξ 2 / π . In the absence of V , an insulator–metal transition takes place, and the TS phase is realized for ξ > π U / 8 t . Phenomenologically, the general quantum phase diagram including insulating and superconducting phases is discussed. [ABSTRACT FROM AUTHOR]

In this paper, we study analytically a one-dimensional half-filled Hubbard model with nearest-neighbor Coulomb repulsion (V) and anisotropic spin exchange (J⊥ ≠ Jz) via the bosonization and renormalization-group (RG) techniques, and establish the rich phase diagrams based on the charge-spin separation hypothesis in the weak-coupling regime. The spin exchange anisotropy induces a non-critical behavior of spin correlations. The result indicates that the spin exchange anisotropy has an important impact on the topological phase diagram of the 1D extended Hubbard model. [ABSTRACT FROM AUTHOR]

By using the field-theoretical techniques combining bosonization with renormalization group, we study a one-dimensional (1D) model of interacting electrons with on-site repulsion (U > 0), nearest-neighbor (nn) exchange (J) and correlated-hopping (t2, t3) interactions at weak coupling. In the case of a half-filled band, the two-body interaction t2 does not influence phase diagram of the model, while the presence of three-body interaction t3 makes the physics of the system highly non-trivial. By a Hartree-Fock decoupling, the effects of t3 bring about hopping of pairs, V-like (nn Coulomb interaction) and isotropic exchange terms in the reduced model Hamiltonian. Interestingly, a negative t3 provides a possibility for the occurrence of the triplet superconductivity in 1D system with purely repulsive interactions (U, J > 0). The ground state phase diagram including the insulating and superconducting phases is discussed analytically. [ABSTRACT FROM AUTHOR]

Using the field theoretical bosonization and renormalization group techniques, we analytically study quantum phase diagram of a one-dimensional half-filled extended Hubbard model with on-site (U) and spin-dependent nearest-neighbor interactions (V⊥, V|) in the weak coupling regime. In the case of easy-plane anisotropy (V⊥ > V|) and at V| < U/2, the existence of bond-ordered spin-density-wave phase, corresponding to spin gapless transverse magnetization located on bonds (BSDW±) is shown. [ABSTRACT FROM AUTHOR]

In this paper, we study the phase diagram of the one-dimensional deformed t-J1-J2 model with frustrated exchange interaction. The introduction of the deformed parameter ζ softens the strength of the induced four- and six-electron interactions caused by the no-double occupancy constraint. For the small ζ and in the weak-coupling regime, we use the bosonization approach and the renormalization group techniques to obtain the phase diagram, which is characterized by the singlet-(SS) and triplet-superconducting (TS), spin-density-wave (SDW) as well as bond-charge-density wave (BCDW) instabilities. The TS and BCDW phases are realized in the whole regime while the SDW and SS correlations depend on J2/J1 < (J2/J1)c or J2/J1 > (J2/J1)c, where (J2/J1)c = 1/3. Furthermore, the deformed model with ζ ≪ 1 is expected to adiabatically connect to the conventional t-J1-J2 model with ζ = 1. [ABSTRACT FROM AUTHOR]

Abstract: The one-dimensional half-filled extended Hubbard model with on-site repulsion (U) and nearest-neighbor interactions including Coulomb repulsion (V) and exchange (J) is studied in the weak-coupling regime. We present a theoretical argument for the occurrence of bond-located phases. The bond–charge–density–wave (BCDW) is realized for and bond–spin–density–wave (BSDW) occurs for . [Copyright &y& Elsevier]

By using the bosonization approach and the renormalization group (RG) technique, we study the half-filled band one-dimensional t-U-J model with additional on-bond repulsion (W>0) in the weak-coupling regime. The presence of on-bond repulsion is responsible for realization of a metallic phase in the system, and the phase diagram is strongly controlled by the symmetry of the model. By analyzing the RG flow diagram and comparing order parameters, the phase boundaries are determined and the structure of the phase diagram is clarified. In the case of SU(2) ⊗ SU(2) symmetry, the phase diagram consists of a metallic phase characterized by a Luttinger liquid (LL) and two insulting phases characterized by the degenerate spin-density-wave (SDW) and the bond-charge-density-wave (BCDW). In the SU(2) ⊗ U(1)-symmetric case, the phase diagram contains two metallic phases: a LL and a Luther-Emery phase, and three insulating phases: the transverse SDW (SDW±), the longitudinal SDW (SDWz) and the dimerized BCDW. The insulating charge-density-wave and bond-spin-density-wave (BSDW) phases are always suppressed in the ground state. In addition, the system show a long-ranged order in the BCDW and SDWz phases. [ABSTRACT FROM AUTHOR]