Effect of Hund coupling in the one-dimensional SU(4) Hubbard model

Lee, Hyun C.; Azaria, P.; Boulat, E.

doi:10.1103/physrevb.69.155109

Cited by 27 publications

(44 citation statements)

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“…When the bare coupling γ is not small the symmetry becomes approximate, but many statements remain valid on a qualitative level [16]. It is particularly important for us that, as was established in [14], [17], [18], that the symmetry itself does not uniquely fix the ground state properties of the model. This is related to the fact that there are transformations of the Hamiltonian which do not change the excitation spectrum, but change the observables.…”

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confidence: 99%

“…This is related to the fact that there are transformations of the Hamiltonian which do not change the excitation spectrum, but change the observables. In [18] it was established that these transformations are automorphisms of the O(8) group. As a consequence, the phase diagram of the ladder includes different phases, some of them are favorable for superconductivity, and some are not (see the discussion in [19] and in Supplemental Material [20]).…”

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confidence: 99%

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Ladder physics in the spin fermion model

Tsvelik

2017

Phys. Rev. B

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A link is established between the spin-fermion (SF) model of the cuprates and the approach based on the analogy between the physics of doped Mott insulators in two dimensions and the physics of fermionic ladders. This enables one to use nonperturbative results derived for fermionic ladders to move beyond the large-N approximation in the SF model. It is shown that the paramagnon exchange postulated in the SF model has exactly the right form to facilitate the emergence of the fully gapped d-Mott state in the region of the Brillouin zone at the hot spots of the Fermi surface. Hence the SF model provides an adequate description of the pseudogap.PACS numbers: 74.81. Fa, 74.90.+n Introduction The purpose of this letter is (i) to establish a link between two successful phenomenological descriptions of the underdoped cuprates and (ii) to use it to obtain some new results. One description is based on the spin-fermion (SF) model [1]; the other one is based on the analogy between the cuprate physics and physics of fermionic ladders. Both approaches have been successful in describing different aspects of the cuprate physics. The SF model provides a natural platform for description of the complicated phase diagram of the cuprates (see, for example, [2] and references therein). The merit of the ladder description, on the other hand, lays in its treatment of the pseudogap. In this approach the formation of pseudogap does not require any translational symmetry breaking which is consistent with the experiments [3][4][5]. The ladder analogy was first put forward by Dagotto and Rice [6]; the insights from models of coupled ladders [7] had eventually lead to the popular expression for the single electron Green's function (the so-called YRZ expression) [8].

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confidence: 99%

Ladder physics in the spin fermion model

Tsvelik

2017

Phys. Rev. B

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“…The analysis of the phase diagram has already been conducted and here we repeat many results obtained in Ref. 13,14,16,20. To keep contact with these works we use a strong tunneling approach introducing bonding (p = 1) and anti-bonding (p = −1) operators…”

Section: Strong Coupling Phases and Order Parametersmentioning

confidence: 87%

“…The low-energy Hamiltonians in different sectors differ by the sign of certain coupling constants and transform to each other by canonical transformations of the fields. These transformations realize authomorphisms of the O(6) group 16 . C. Emergent attractive interactions.…”

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confidence: 99%

Excitation spectrum of doped two-leg ladders: A field theory analysis

Controzzi

Tsvelik

2005

Phys. Rev. B

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We apply quantum field theory to study the excitation spectrum of doped two-leg ladders. It follows from our analysis that throughout most of the phase diagram the spectrum consists of degenerate quartets of kinks and anti-kinks and a multiplet of vector particles split according to the symmetry of the problem as 3 + 2 +1. This basic picture experiences corrections when one moves through the phase diagram. In some regions the splitting may become very small and in others it is so large that some multiplets are pushed in the continuum and become unstable. At second order transition lines masses of certain particles vanish. Very close to the first order transition line additional generations of particles emerge. Strong interactions in some sectors may generate additional bound states (like breathers) in the asymmetric charge sector. We briefly describe the properties of various correlation functions in different phases.

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“…This kink structure originates in the spin-orbital SU(4) symmetry which realizes at a special point J=λ=0. [15][16][17][18][19] At the SU(4) symmetric point, correlations of spin S i and orbital pseudospin…”

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confidence: 99%

Multipole Correlations oft_2g-Orbital Hubbard Model with Spin–Orbit Coupling

Onishi

2011

J. Phys. Soc. Jpn.

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We investigate the ground-state properties of a one-dimensional t 2g -orbital Hubbard model including an atomic spin-orbit coupling by using numerical methods, such as Lanczos diagonalization and densitymatrix renormalization group. As the spin-orbit coupling increases, we find a ground-state transition from a paramegnetic state to a ferromagnetic state. In the ferromagnetic state, since the spin-orbit coupling mixes spin and orbital states with complex number coefficients, an antiferro-orbital state with complex orbitals appears. According to the appearance of the complex orbital state, we observe an enhancement of Γ 4u octupole correlations.KEYWORDS: t 2g orbitals, spin-orbit coupling, multipole, density-matrix renormalization groupThe competition and cooperation between spin and orbital degrees of freedom in strongly correlated electron systems manifest itself in the emergence of various types of spinorbital ordered and quantum liquid phases. [1][2][3] In general, among competing interactions involving spin and orbital, the spin-orbit coupling is supposed to be weak in 3d transitionmetal oxides such as cupurates and manganites, while as we move to 4d and 5d electrons, the spin-orbit coupling becomes strong and responsible for magnetic, transport, and optical properties. When the spin-orbit coupling is dominant, spin and orbital are not independent, but instead the total angular momentum gives a good description of the many-body state. In fact, it has been suggested that Sr 2 IrO 4 , in which Ir 4+ ions have five electrons in triply degenerate t 2g orbitals, exhibits a novel Mott-insulating state with an effective total angular momentum J eff =1/2 due to a strong spin-orbit coupling. 4-7)In the limit of strong spin-orbit coupling, the ground-state Kramers doublet at a local ion can be described by an isospin with J eff =1/2. 8, 9) The exchange interaction among isospins can lead to a variety of ordering and fluctuation phenomena of spin-orbital entangled states.When we move to heavy-element f -electron systems such as rare-earth and actinide compounds, the spin-orbit coupling is large comparing with other energy scales. In such a case, we usually classify the complicated spin-orbital state from the viewpoint of multipole, which is described by the total angular momentum. Indeed, the multipole physics has been actively discussed in the field of heavy electrons.10) A recent trend is to unveil exotic high-order multipole ordering. As an attempt to clarify multipole properties of f -electron systems from a microscopic viewpoint, we have numerically studied multipole correlations of an f -orbital Hubbard model on the basis of the j-j coupling scheme.11) We believe that it is also important to clarify multipole properties in d-electron systems under the effect of the spin-orbit coupling.In this paper, we investigate multipole properties in the ground state of a one-dimensional t 2g -orbital Hubbard model including the spin-orbit coupling by numerical methods. With increasing the spin-orbit coupling, the ground state...

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Effect of Hund coupling in the one-dimensional SU(4) Hubbard model

Cited by 27 publications

References 26 publications

Ladder physics in the spin fermion model

Ladder physics in the spin fermion model

Excitation spectrum of doped two-leg ladders: A field theory analysis

Multipole Correlations oft_2g-Orbital Hubbard Model with Spin–Orbit Coupling

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Effect of Hund coupling in the one-dimensional SU(4) Hubbard model

Cited by 27 publications

References 26 publications

Ladder physics in the spin fermion model

Ladder physics in the spin fermion model

Excitation spectrum of doped two-leg ladders: A field theory analysis

Multipole Correlations oft2g-Orbital Hubbard Model with Spin–Orbit Coupling

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Product

Resources

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Multipole Correlations oft_2g-Orbital Hubbard Model with Spin–Orbit Coupling