Theory of the reentrant charge-order transition in the manganites

Hellberg, C. Stephen

doi:10.1063/1.1358326

Cited by 19 publications

(22 citation statements)

References 19 publications

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“…The metallic and charge-ordered (CO) phases are separated by a "reentrant" charge-ordering transition line T CO . Such "reentrant" behavior is consistent [28] with previous studies of the quarter-filled extended Hubbard model using FLEX [29] and its extensions with vertex corrections [30] DMFT [31] and exact diagonalization [32]. In the metallic phase close to CO, where Li 0.9 Mo 6 O 17 is presumably located, charge fluctuations with Q = (0,π/(b/2),π/(c/2)) are strongly enhanced (see inset of Fig.…”

Section: A Phase Diagramsupporting

confidence: 77%

Charge fluctuations in the unconventional metallic state ofLi0.9Mo6O17

Merino

Álvarez

2015

Phys. Rev. B

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Charge fluctuations in the quasi-one-dimensional material Li 0.9 Mo 6 O 17 are analyzed based on a multiorbital extended Hubbard model. A charge-ordering transition induced by Coulomb repulsion is found with a particular charge-ordering pattern. The metallic phase is characterized by the presence of a charge collective mode which softens signaling the proximity to the charge order transition. We argue that the scattering between electrons mediated by these charge fluctuations can lead to non-Fermi liquid behavior in a quasi-one-dimensional system consistent with the unconventional metallic behavior observed above the superconducting transition in Li 0.9 Mo 6 O 17 .

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Section: A Phase Diagramsupporting

confidence: 77%

Charge fluctuations in the unconventional metallic state ofLi0.9Mo6O17

Merino

Álvarez

2015

Phys. Rev. B

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“…By using Cluster Perturbation Theory (CPT), the finite temperature spectral function is extended to the infinite system, clearly exhibiting the effects of spin-charge separation. [14,15]. In principle this method can be applied at all temperatures, but at low temperatures the required number of random samples is very large.…”

mentioning

confidence: 99%

“…The Finite Temperature Lanczos Method (FTLM), introduced by Jaklič and Prelovšek [1], has in recent years allowed the precise calculation of thermodynamic quantities of strongly correlated systems. It has been applied to the t-J model for the cuprates [2,3,4,5,6,7,8] and vanadates [9,10], orbital t-J model [11], Kondo lattice model [12], Heisenberg model [13] and static properties of the Hubbard model [14,15]. In principle this method can be applied at all temperatures, but at low temperatures the required number of random samples is very large.…”

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confidence: 99%

Low-temperature Lanczos method for strongly correlated systems

et al. 2003

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We present a modified finite temperature Lanczos method for the evaluation of dynamical and static quantities of strongly correlated electron systems that complements the finite temperature method (FTLM) introduced by Jaklič and Prelovšek for low temperatures. Together they allow accurate calculations at any temperature with moderate effort. As an example we calculate the static spin correlation function and the regular part of the optical conductivity σ reg (ω) of the one dimensional Hubbard model at half-filling and show in detail the connection between the ground state and finite temperature method. By using Cluster Perturbation Theory (CPT), the finite temperature spectral function is extended to the infinite system, clearly exhibiting the effects of spin-charge separation. [14,15]. In principle this method can be applied at all temperatures, but at low temperatures the required number of random samples is very large. FTLM is restricted to small systems and particularly at low temperatures, finite size effects become important. They can be overcome, at least for properties derived from the single particle Green's function, by using Cluster Perturbation Theory (CPT) [16,17], which provides infinite system results with remarkable accuracy [18]. However, CPT requires finite cluster Greens functions G ab (ω) for all sites a, b, increasing the number of required Lanczos runs and matrix elements by a factor equal to the number of lattice sites. It therefore requires a sufficiently fast low temperature method.In this paper we present a modified finite temperature Lanczos method which allows to calculate properties for large Hilbert spaces at low temperatures that are not accessible by the existing method. We show that a combination of our low temperature Lanczos method (LTLM) with the FTLM allows an accurate calculation of thermodynamic properties at any temperature with moderate effort.Let us first present the existing FTLM. For the case of a static expectation value of an operator Owith β = 1/T (k B =h = 1) and a sum over a complete orthonormal basis set |n , the FTLM approximation iswith a sum over symmetry sectors s of dimension N s , and R random vectors |r in each sector [19]. M is the number of Lanczos steps. For each random vector |r , a Lanczos procedure is performed, yielding M eigenenergies ε For dynamical correlation functions C(t) = A(t)B , FTLM calculatesHere, an initial vectoris used to generate additional eigenenergiesε and similarly for (3). Thus the ground state result will suffer from severe statistical fluctuations, although the exact (Lanczos) eigenvector |Ψ 0 is reached with every |r and one random vector should be sufficient. Yet, FTLM gets worse with decreasing temperature T .

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“…38,39) All these Q1D molecular conductors show no anomaly in the bulk χ σ (T ) at T = T CO , while NMR measurements show the appearance of atomic sites showing different Knight shifts and relaxation rates: 40,41) these are also consistent with our analysis. Recently, several Q1D compounds without dimerization have been synthesized where a CO transition is suggested, such as (o-DMTTF) 2 Br 42) and (EDT-TTF-CONMe) 2 X [X= AsF 6 and Br]. 43,44) There, as in (DI-DCNQI) 2 Ag at ambient pressure, the anomaly at T = T CO in ρ(T ) is not clearly seen possibly due to the strong fluctuation which may be underestimated in our calculation due to the interchain mean-field treatment.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…Different techniques beyond the mean-field approximation have been applied to investigate the finite-T properties of this model, such as exact diagonalization (ED), 6) slave-boson, 7) dynamical meanfield, 8,9) correlator projection, 10) and quantum Monte Carlo (QMC) 11) methods. However, due to theoretical difficulties, the physical properties across T CO such as the spin susceptibility and the electrical resistivity are not elucidated, and the interplay between spin and charge degrees of freedom is not fully explored yet.…”

Section: Introductionmentioning

confidence: 99%

Finite-Temperature Properties across the Charge Ordering Transition –Combined Bosonization, Renormalization Group, and Numerical Methods–

et al. 2010

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We theoretically describe the charge ordering (CO) metal-insulator transition based on a quasi-onedimensional extended Hubbard model, and investigate the finite temperature (T ) properties across the transition temperature, TCO. In order to calculate T dependence of physical quantities such as the spin susceptibility and the electrical resistivity, both above and below TCO, a theoretical scheme is developed which combines analytical methods with numerical calculations. We take advantage of the renormalization group equations derived from the effective bosonized Hamiltonian, where Lanczos exact diagonalization data are chosen as initial parameters, while the CO order parameter at finite-T is determined by quantum Monte Carlo simulations. The results show that the spin susceptibility does not show a steep singularity at TCO, and it slightly increases compared to the case without CO because of the suppression of the spin velocity. In contrast, the resistivity exhibits a sudden increase at TCO, below which a characteristic T dependence is observed. We also compare our results with experiments on molecular conductors as well as transition metal oxides showing CO.

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Theory of the reentrant charge-order transition in the manganites

Cited by 19 publications

References 19 publications

Charge fluctuations in the unconventional metallic state ofLi0.9Mo6O17

Charge fluctuations in the unconventional metallic state ofLi0.9Mo6O17

Low-temperature Lanczos method for strongly correlated systems

Finite-Temperature Properties across the Charge Ordering Transition –Combined Bosonization, Renormalization Group, and Numerical Methods–

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