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Edegger, Bernhard; Evertz, Hans Gerd; Noack, R. M.

doi:10.1103/physrevb.72.085131

Cited by 13 publications

(23 citation statements)

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“…However, on an isolated ladder [7,8] the spin gap vanishes in the thermodynamic limit. The occurrence of the spin gap in NaV 2 O 5 appears to be intimately connected to the coupling of ladders, as indicated, e.g., by the splitting of magnon branches [4,12,13].…”

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confidence: 95%

“…In a recent DensityMatrix Renormalization Group (DMRG) study [8], we showed that the inclusion of a strong effective Holstein coupling to the lattice, which was found in local-density approximation (LDA) calculations [11], reduces the required Coulomb repulsion to a realistic value. The DMRG calculations then yielded good agreement between theoretical and experimental results for the amount of charge order, the extent of lattice distortion in the c direction, the effective spin coupling J eff in the b direction, and the charge gap.However, on an isolated ladder [7,8] the spin gap vanishes in the thermodynamic limit. The occurrence of the spin gap in NaV 2 O 5 appears to be intimately connected to the coupling of ladders, as indicated, e.g., by the splitting of magnon branches [4,12,13].…”

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confidence: 98%

“…They can be described by an extended Hubbard model (EHM) [2]. A zigzag charge order as observed in NaV 2 O 5 [4] is already created in this model by the nearestneighbor Coulomb repulsion V for an isolated ladder, but only at overly large values of V [5][6][7][8][9][10]. In a recent DensityMatrix Renormalization Group (DMRG) study [8], we showed that the inclusion of a strong effective Holstein coupling to the lattice, which was found in local-density approximation (LDA) calculations [11], reduces the required Coulomb repulsion to a realistic value.…”

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Creation and Destruction of a Spin Gap in Weakly Coupled Quarter-Filled Ladders

2006

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We investigate weakly coupled quarter-filled ladders with model parameters relevant for NaV(2)O(5) using density-matrix renormalization group calculations on an extended Hubbard model coupled to the lattice. NaV(2)O(5) exhibits super-antiferroelectric charge order with a zigzag pattern on each ladder. We show that this order causes a spin dimerization along the ladder and is accompanied by a spin gap of the same magnitude as that observed experimentally. The spin gap is destroyed again at large charge order due to a restructuring of the spins. An analysis of an effective spin model predicts a recreation of the gap by interladder singlets when the charge order increases further.

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Creation and Destruction of a Spin Gap in Weakly Coupled Quarter-Filled Ladders

2006

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“…The "distracting" terms which are ignored are, [1], correlated hopping terms caused by the transformation which modify the t ij somewhat (Edegger 3 has estimated their effect in some detail); [2] phonon-mediated interactions, which to lowest order simply modify U, the remainder being small compared to J; [3] the longer-range coulomb interactions which play a role in the mesoscopic charge instabilities (like stripes) which are manifest for low doping and low temperatures, but don't affect the big picture. All can be included as extra terms in the projective Hamiltonian [3] (but must be projected).…”

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confidence: 99%

“…Low-energy solutions of [3] are necessarily of the form ! " = P#(r 1 ,r 2 ,L,r N ), where # is a general function of all electron positions.…”

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Hidden Fermi liquid: The secret of high-Tccuprates

Anderson

2008

Phys. Rev. B

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Astract-I present a formalism for dealing directly with the effects of the Gutzwiller projection, which is implicit in the t-J model widely believed to underly the phenomenology of the high-Tc cuprates. I suggest that a true BCS condensation from a Fermi liquid state takes place, but in the unphysical space prior to projection. The theory which results upon projection does not follow conventional rules of diagram theory and in fact in the normal state is a Z=0 non-Fermi liquid. Anomalous properties of the 'strange metal" normal state are predicted and compared to experiments.

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Finite-temperature investigation of quarter filled ladder systems

Gabriel

Sherman

Lang

et al. 2005

Physica B: Condensed Matter

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We investigate charge ordering in a quarter-filled ladder at finite temperature by determinantal Quantum Monte Carlo. The sign problem is moderate in a wide range of model parameters relevant for NaV2O5. The charge order parameter exhibits a crossover as a function of inverse temperature β on finite systems. Above a critical nearest neighbor Coulomb repulsion Vc, the correlation length grows exponentially with β, indicative of the ordered phase at β = ∞. We find a clear single-particle gap manifesting itself in a flat n(µ) dependence at large nearest neighbor Coulomb repulsion V . Key words:quarter-filled ladders, charge ordering, quantum Monte CarloThe inorganic ladder compound NaV2O5 has attracted great attention in recent years. This interest was triggered by magnetic susceptibility measurements [1], which show a phase transition at T = 34 K into a low-temperature spin-gapped phase. This transition is accompanied by charge ordering, as observed in NMR measurements [2], where the valence of the vanadium sites changes from V 4.5 to V 4.5±δ , with δ the amount of charge disproportion. This transition has been studied theoretically by several techniques at T = 0 [3].On a microscopic level the system can be described by an extended Hubbard modelat quarter filling n = 0.5, with hopping matrix elements tij = tx along the ladder and tij = ty within a rung, and chemical potential µ. We state all energies in units of ty. These hopping parameters as well as the onsite Coulomb interaction can be extracted from firstprinciple calculations [4]. The hopping along chains * Corresponding author: e-mail: evertz@tugraz.at tx ≃ 0.5ty is weaker than along rungs. This strongly influences the physics of the ladder, for which a spingap seems to appear at tx > ∼ ty [3]. We used tx = 0.5 and U = 8. Since the non-local Coulomb interaction V cannot be determined properly by band-structure calculations, we used V as a free parameter of the Hamiltonian. The charge order parameter is ∆ 2 co = 1 2L n ij e iQ(r i −r j ) (ni − n )(nj − n ) with Q = (π, π), which is unity for complete ordering.We performed grand canonical calculations by determinantal quantum Monte Carlo. These are often very difficult for doped systems because of a sign problem. Fortunately, the average sign is favorably large in the relevant parameter range of tx/ty = 0.5 and large V (Fig. 1). In the opposite case of isotropic tx = ty at small V , sign becomes very small. The charge order parameter exhibits similar behavior, but it is less strongly dependent on tx/ty. Charge order grows with increasing V . Fig. 2 shows the charge correlation length ξcc. At small interactions, V = 1.5 and 2.0, the correlation length seems to saturate, but for V = 2.5 and 3.0 it increases exponentially with β, with a V -dependent slope. This behavior is consistent with the 1D Ising model in a transverse field (IMTF) [5], which is equiv-

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Charge order induced by electron-lattice interaction inNaV2O5

Cited by 13 publications

References 50 publications

Creation and Destruction of a Spin Gap in Weakly Coupled Quarter-Filled Ladders

Creation and Destruction of a Spin Gap in Weakly Coupled Quarter-Filled Ladders

Hidden Fermi liquid: The secret of high-Tccuprates

Finite-temperature investigation of quarter filled ladder systems

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