Nature of the insulating phases in the half-filled ionic Hubbard model

Kampf, Arno P.; Sekania, Michael; Japaridze, G. I.; Brune, Philipp

doi:10.1088/0953-8984/15/34/319

Cited by 85 publications

(134 citation statements)

References 47 publications

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“…5,6 As in the covalent insulator, ∆ c and ∆ s decrease with increasing U . However, the transition to the Mott insulator proceeds via an intermediate insulating phase with bond order and a staggered modulation of the kinetic energy on neighboring bonds.…”

Section: Spin Excitations In the Band Insulatormentioning

confidence: 97%

Correlations in a band insulator

et al. 2009

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We study a model of a covalent band insulator with on-site Coulomb repulsion at half-filling using dynamical mean-field theory. Upon increasing the interaction strength the system undergoes a discontinuous transition from a correlated band insulator to a Mott insulator with hysteretic behavior at low temperatures. Increasing the temperature in the band insulator close to the insulator-insulator transition we find a crossover to a Mott insulator at elevated temperatures. Remarkably, correlations decrease the energy gap in the correlated band insulator. The gap renormalization can be traced to the low-frequency behavior of the self-energy, analogously to the quasiparticle renormalization in a Fermi liquid. While the uncorrelated band insulator is characterized by a single gap for both charge and spin excitations, the spin gap is smaller than the charge gap in the correlated system.

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Section: Spin Excitations In the Band Insulatormentioning

confidence: 97%

Correlations in a band insulator

et al. 2009

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“…To settle this issue one must turn to bond-bond correlations, which have been extensively studied recently by several authors. [4][5][6][7][8][9][10] These correlations tell us that our second phase is indeed spontaneously dimerized and therefore the detected transition may correspond to the critical point of the well-known two-point scenario. The second critical point, associated with the spin gap, cannot be detected by the SWF.…”

Section: Discussionmentioning

confidence: 84%

“…It never vanishes, in agreement with recent findings. 6,10 This change of regime, signaled by an abrupt transfer of spectral weight from the inner to the outer peaks, can be easily traced to the ionic-neutral transition known for many years 2,3 to take place in the IHM. The noninteracting band structure k =−2t cos k vanishes at k F = ± / 2, leading to the isolated atoms limit, with the well-known DOS…”

Section: Critical Behavior Of the Low-energy Band Structurementioning

confidence: 97%

“…An important and controversial issue is the nature of this transition as well as whether two critical points rather than one separate both phases. Depending on the method of calculation used, either one [4][5][6] or two [7][8][9][10] critical points have been predicted, so that the controversy cannot be considered as completely closed yet, although some consensus is growing in favor of a two-point scenario.…”

Section: Introductionmentioning

confidence: 99%

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Critical behavior of the single-particle spectral weight in the ionic Hubbard model

2005

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We show in this paper that the single-particle spectral-weight function ͑SWF͒ of the one-dimensional ionic Hubbard model at half filling exhibits critical behavior, as a function of the on-site repulsion U, near the chemical potential. The calculation has been carried out within the framework of the cluster perturbation theory approach of Senechal et al., Phys. Rev. Lett 84, 522 ͑2000͒. As U increases, the SWF at k F = ± /2 ͑the Fermi points͒ jumps from the two-peak structure ͑plus two weak side peaks͒ characteristic of low U Ͻ U c to a four-peak structure beyond U c where all the peaks have about the same spectral weight. This abrupt spectralweight transfer from the inner to the outer peaks can be traced to the ionic-neutral transition characteristic of this system and seems to correspond to the first critical point of the two-point scenario discussed in the literature. It is accompanied by a nonvanishing minimum of the single-particle charge gap. As U increases further, the system evolves gradually into a Mott-Hubbard insulator. No other signatures of abrupt change are detected in the SWF. These results are discussed in the light of photoelectron spectroscopic measurements of quasi-one-dimensional materials.

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“…We presume that it is a divergent power-law as it is found in the sine-Gordon model at particular values of the interaction 45 . The vanishing of the spin gap and the stabilization of the MI phase in the 1D IHM has been discussed before on the basis of quantum Monte Carlo results 46 and DMRG results 15,47 without clear-cut conclusion. Although the position of the second transition point U c2 between the SDI and the MI is not determined accurately in our investigation, our results provide clear evidence that the MI phase is stable in the large-U limit.…”

Section: Mott Insulator Phasementioning

confidence: 99%

From gapped excitons to gapless triplons in one dimension

2015

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Often, exotic phases appear in the phase diagrams between conventional phases. Their elementary excitations are of particular interest. Here, we consider the example of the ionic Hubbard model in one dimension. This model is a band insulator (BI) for weak interaction and a Mott insulator (MI) for strong interaction. Inbetween, a spontaneously dimerized insulator (SDI) occurs which is governed by energetically low-lying charge and spin degrees of freedom. Applying a systematically controlled version of the continuous unitary transformations (CUTs) we are able to determine the dispersions of the elementary charge and spin excitations and of their most relevant bound states on equal footing. The key idea is to start from an externally dimerized system using the relative weak interdimer coupling as small expansion parameter which finally is set to unity to recover the original model.

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Nature of the insulating phases in the half-filled ionic Hubbard model

Cited by 85 publications

References 47 publications

Correlations in a band insulator

Correlations in a band insulator

Critical behavior of the single-particle spectral weight in the ionic Hubbard model

From gapped excitons to gapless triplons in one dimension

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