PHASE DIAGRAM OF ONE-DIMENSIONAL t–U–J MODEL WITH ANISOTROPIC ANTIFERROMAGNETIC EXCHANGE

2010 ◽  
Vol 24 (28) ◽  
pp. 2769-2783 ◽  
Author(s):  
HANQIN DING ◽  
YANSHEN WANG
Keyword(s):  
Phase Diagram ◽  
Weak Coupling ◽  
Density Wave ◽  
Spin Density Wave ◽  
Spin Excitation ◽  
Antiferromagnetic Exchange ◽  
Weak Coupling Regime ◽  
One Dimensional ◽  
Bond Charge ◽  
Umklapp Scattering

By using the bosonization approach and the weak-coupling renormalization group (RG) techniques, we study the phase diagram of one-dimensional half-filled t–U–J model parametrized by exchange anisotropy λ (0 ≤ λ ≤ 2) in the weak-coupling regime. In the case of anisotropic antiferromagnetic exchange (J > 0) and on-site repulsion (U > 0), the ground state is characterized by the spin-density-wave (SDW) and bond-charge-density-wave (BCDW) insulating phases. We identify the SDW correlation corresponding to the transverse SDW± phases with a gapless spin excitation (Δs=0) for λ < 4/3 and to the longitudinal SDWz phase with a spin gap (Δs > 0) for λ > 4/3, respectively. The charge excitation is always gapped (Δc > 0) in the whole regime, and the BCDW and SDWz phases show a long-range order. We also examine effects of the nonlocal Umklapp scattering of parallel-spin electrons, which play a role to weaken the BCDW phase and to enhance the SDW phase slightly. The results demonstrate that the properties of our model are not identical with those of the conventional t–U–J model.

PHASE DIAGRAM OF ONE-DIMENSIONAL DEFORMED t–J1–J2 MODEL WITH FRUSTRATED EXCHANGE INTERACTION

2011 ◽  
Vol 25 (17) ◽  
pp. 1441-1455 ◽  
Author(s):  
HANQIN DING ◽  
JUN ZHANG
Keyword(s):  
Phase Diagram ◽  
Exchange Interaction ◽  
Charge Density Wave ◽  
Weak Coupling ◽  
Density Wave ◽  
Spin Density Wave ◽  
Weak Coupling Regime ◽  
One Dimensional ◽  
The One ◽  
Bond Charge

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.

SPIN GAPLESS BOND-ORDERED PHASE IN THE EXTENDED HUBBARD CHAIN WITH SPIN-DEPENDENT REPULSION

2011 ◽  
Vol 25 (27) ◽  
pp. 3555-3568 ◽  
Author(s):  
HANQIN DING ◽  
JUN ZHANG
Keyword(s):  
Phase Diagram ◽  
Renormalization Group ◽  
Weak Coupling ◽  
Nearest Neighbor ◽  
Density Wave ◽  
Spin Density Wave ◽  
Extended Hubbard Model ◽  
Weak Coupling Regime ◽  
One Dimensional ◽  
Plane Anisotropy

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.

PHASE DIAGRAM OF THE ONE-DIMENSIONAL t–U–J MODEL WITH ON-BOND REPULSION AT HALF FILLING

2010 ◽  
Vol 24 (32) ◽  
pp. 6307-6322 ◽  
Author(s):  
HANQIN DING ◽  
YANSHEN WANG
Keyword(s):  
Phase Diagram ◽  
Charge Density ◽  
Spin Density ◽  
Charge Density Wave ◽  
Density Wave ◽  
Spin Density Wave ◽  
Metallic Phase ◽  
Flow Diagram ◽  
One Dimensional ◽  
Bond Charge

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 ( SDW z) 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 SDW z phases.

WEAK-COUPLING PHASE DIAGRAM OF THE ONE-DIMENSIONAL DEFORMED T-J MODEL

2007 ◽  
Vol 22 (07n10) ◽  
pp. 733-740 ◽  
Author(s):  
QINGSHAN MA ◽  
JIANHUI DAI ◽  
ZHAOXIN XU ◽  
JUN ZHANG
Keyword(s):  
Phase Diagram ◽  
Density Wave ◽  
Spin Density Wave ◽  
One Dimension ◽  
Antiferromagnetic Exchange ◽  
One Dimensional ◽  
Half Filling ◽  
The One ◽  
Hubbard Operators ◽  
Ground State Phases

The deformed t-J lattice model is defined by replacing the fermion operators by the deformed Hubbard operators in the t-term but without changing the J-term in the conventional t-J model. The physics of this model was argued to be continuously connected to those of the t-J one when the deformation parameter λ varies from zero to unit. In this paper, by using the bosonization field theory and renormalization group technique, we study the phase diagram of the one dimension deformed t-J model in the regime where λ and J/t are both positively small but comparable to each other. By explicitly incorporating the contributions from the deformation-induced six-particle term and the antiferromagnetic exchange interaction, we find that at half-filling the system shows three distinct ground states characterized by the Luttinger liquid, the spin-density-wave and the bond-order-wave, respectively. These results indicate that the ground state phases of the deformed t-J model is neither connected smoothly to those of the system at λ = 1 nor to those of the conventional t-J model.

Phase diagram of an extended t-U-J chain with frustrated exchange interaction

2014 ◽  
Vol 28 (32) ◽  
pp. 1450228
Author(s):  
Hanqin Ding ◽  
Jun Zhang
Keyword(s):  
Phase Diagram ◽  
Charge Density ◽  
Charge Density Wave ◽  
Nearest Neighbor ◽  
Spin Exchange ◽  
Density Wave ◽  
Spin Density Wave ◽  
Effective Field ◽  
J Chain ◽  
Bond Charge

Using the low-energy effective field theory scenario combined Abelian bosonization and renormalization-group techniques, we study the Hubbard chain with additional anisotropic nearest-neighbor and isotropic next-nearest-neighbor spin exchanges J and J′ in the weak-coupling regime. The spin correlations are non-critical due to the anisotropic J (Jxy ≠ Jz). The frustrating antiferromagnetic exchange J′ leads to an enhancement of the dimerized phase and induces a long-range charge-density-wave (CDW) phase. For smaller values of J′ (J′ < 2U/3), the quantum phase diagram consists of the insulating spin-density-wave ( SDW xy, SDW z) and bond-charge-density-wave (BCDW) phases and the triplet superconducting ( TS 0, TS ±) phase. For larger J′ (J′ ≥ 2U/3), a finite CDW phase appears. The result shows that the frustrated spin exchange J′ changes the topological structure of the usual t-U-J chain.

Tuning of Spin Density Wave Strengths in Quasi-One-Dimensional Halogen-Bridged NiIIIComplexes with Strong Electron Correlations, [NiIII(chxn)2X]Y2

1999 ◽  
Vol 38 (8) ◽  
pp. 1894-1899 ◽  
Author(s):  
Masahiro Yamashita ◽  
Toshio Manabe ◽  
Kazuo Inoue ◽  
Takuya Kawashima ◽  
Hiroshi Okamoto ◽  
...  
Keyword(s):  
Spin Density ◽  
Density Wave ◽  
Spin Density Wave ◽  
Electron Correlations ◽  
Strong Electron ◽  
One Dimensional ◽  
Strong Electron Correlations

Spin density wave – metal (superconductor) competition: A phase segregation scenario

2002 ◽  
Vol 12 (9) ◽  
pp. 61-64
Author(s):  
C. Pasquier ◽  
M. Héritier ◽  
D. Jérome
Keyword(s):  
Free Energy ◽  
Dispersion Relation ◽  
Fermi Level ◽  
Spin Density ◽  
Density Wave ◽  
Spin Density Wave ◽  
Phase Segregation ◽  
Organic Conductor ◽  
One Dimensional ◽  
Unique Parameter

We present a model comparing the free energy of a phase exhibiting a segregation between spin density wave (SDW) and metallic domains (eventually superconducting domains) and the free energy of homogeneous phases which explains the findings observed recently in (TMTSF)2PF6. The dispersion relation of this quasi-one-dimensional organic conductor is linearized around the Fermi level. Deviations from perfect nesting which stabilizes the SDW state are described by a unique parameter t$'_b$, this parameter can be the pressure as well.

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