Short-range Coulomb correlations render massive Dirac fermions massless

Ebrahimkhas, Morad; Jafari, S. A.

doi:10.1209/0295-5075/98/27009

Cited by 19 publications

(31 citation statements)

References 29 publications

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“…The dashed lines in Fig. 8 diagram [27] with that of Fig. 7 we find that the phase boundaries obtained from present study (bold lines) partition the BI and SM phase of the DMFT phase diagram into three phase corresponding to normal, Ising and orthogonal variants.…”

supporting

confidence: 69%

“…The method of dynamical mean field theory was also applied to study the quantum phase transitions of the ionic Hubbard model on the honeycomb lattice. Starting from massive Dirac fermions on the honeycomb lattice the competition between U and the single-particle gap parameter ∆ (known as mass term when it comes to Dirac fermions) gives rise to massless Dirac fermions [27]. A recent strong coupling expansion gives a quantum critical semi-metallic state [7].…”

Section: Introductionmentioning

confidence: 99%

“…The Ising order parameter vanishes at U ⊥ beyond which the semiconducting transport will be entirely done by spinons. For largest values of U > U Mott the system eventually becomes Mott insulating [27].The existence of a region where the Ising variable is ordered, but the rotor variable is disordered endows the nonMott phase of the ionic Hubbard model with a condensate of paired charge bosons whence charge fluctuations survive in the form of Ising variables. In the ionic Hubbrard model this corresponds to Ising band insulating phase where the kinetic energy of spinon Hamiltonian is controlled by an Ising order parameter, and hence the band properties of such a semiconducting phase inherits characteristic temperature and field dependence from the underlying Ising model.…”

mentioning

confidence: 99%

“…If we keep increasing ∆ beyond ∼ 0.38 the OBI phase also gets a chance. However if the DMFT scenario of battle between U and ∆ suggests that the OBI phase does not directly transform into Mott phase, but instead goes through an orthogonal semi metal which is appealing: The battle will continue in the fractionalized OBI phase of spinons and can presumably close the spinon gap in OBI to render it OSM before getting into Mott phase [27].Within the present mean field approximate treatment of the IBI-OBI phase transition, the thermal probes are coupled to spinons that are independent of Ising pseudo-spins. The optical probe on the other hand always couples to the spinons.…”

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confidence: 99%

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Semiconductor of spinons: from Ising band insulator to orthogonal band insulator

Farajollahpour¹,

Jafari²

2017

J. Phys.: Condens. Matter

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Within the ionic Hubbard model, electron correlations transmute the single-particle gap of a band insulator into a Mott gap in the strong correlation limit. However understanding the nature of possible phases in between these two extreme insulating phases remains an outstanding challenge. We find two strongly correlated insulating phases in between the above extremes: (i) The insulating phase just before the Mott phase can be viewed as gapping a non-Fermi liquid state of spinons through staggered ionic potential. The quasi-particles of underlying spinons are orthogonal to physical electrons and hence they do not couple to photoemission probes, giving rise to "ARPES-dark" state due to which the ARPES gap will be larger than optical and thermal gap. (ii) The correlated insulating phase just after the normal band insulator corresponds to the ordered phase of slave Ising spins (Ising insulator) where charge configuration is controlled by an underlying Ising variable which indirectly couples to external magnetic field and hence gives rise to additional temperature and field dependence in semiconducting properties. In the absence of tunability for the Hubbard U , such a temperature and field dependence can be conveniently employed to achieve further control on the transport properties of Ising-based semiconductors. The rare earth monochalcogenide semiconductors where the magneto-resistance is anomalously large can be a candidate system for the ordered phase of Ising variable where pairs of charge bosons are condensed in the background. Combining present results with our previous dynamical mean field theory study, we argue that the present picture holds if the ionic potential is strong enough to survive the downward renormalization of the ionic potential caused by Hubbard U . 71.27.+a, 71.30.+h INTRODUCTIONElectron conduction in periodic structures can cease for two reasons. The simplest is to couple single-particle states across a reduced Brillouin zone by an off-diagonal matrix elements due to reduction in the periodicity. However the second and more exciting way is to introduce strong electron correlations where due to Coulomb interactions, as suggested by N. Mott, electron conduction in an otherwise conducting state is interrupted [1]. This may seem to suggest that strong correlation has its most dramatic effect on metals by transforming them into many-body Mott insulators. The canonical model within which the metal-to-insulator transition (MIT) problem is investigated is the Hubbard model [2]. Efforts to understand the nature of MIT has lead to many technical [3][4][5][6][7][8][9][10][11][12][13][14] and conceptual [15][16][17][18][19] developments providing clues into possible mechanisms of non-Fermi liquid formation.But even more challenging question is what happens when both mechanisms of gap formation are simultaneously present, i.e. what are the properties of strongly correlated band insulators or semiconductors? Let us formalize the problem as follows: Imagine a staggered potential of strength ∆ (the io...

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supporting

confidence: 69%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Semiconductor of spinons: from Ising band insulator to orthogonal band insulator

Farajollahpour¹,

Jafari²

2017

J. Phys.: Condens. Matter

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“…The details of calculations are done in previous work [6]. The DOS of an interaction system can be calculated by,…”

Section: Model and Methodsmentioning

confidence: 99%

Effects of correlations on honeycomb lattice in ionic-Hubbard model

2015

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In a honeycomb lattice the symmetry has been broken by adding an ionic potential and a single-particle gap was generated in the spectrum. We have employed the iterative perturbation theory (IPT) in dynamical mean field approximation method to study the effects of competition between U and ∆ on energy gap and renormalized Fermi velocity. We found, the competition between the single-particle gap parameter and the Hubbard potential closed the energy gap and restored the semi-metallic phase, then the gap is opened again in Mott insulator phase. For a fixed ∆ by increasing U , the renormalized Fermi velocityṽ F is decreased, but change in ∆, for a fixed U , has no effects onṽ F . The difference in filling factor is calculated for various number of U, ∆. The results of this study can be implicated for gapped graphene e.g. hydrogenated graphene.

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Quantum Integrability of 1D Ionic Hubbard Model

Hosseinzadeh

Jafari

2020

Annalen der Physik

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The quantum integrability of the 1D ionic Hubbard model (IHM) is established using two independent numerical methods, namely i) energy level spacing statistics and ii) occupation profile of one‐particle density matrix (OPDM) eigen‐values. Both methods suggest that the 1D IHM is integrable. The calculations of energy level statistics reproduce the known results for the standard Hubbard model. Upon turning on the the ionic term, the energy level spacing distribution of this model continues to obey the Poissonian distribution. Occupation patterns as extracted from OPDM indicate that quasi‐particles are sharpened upon increasing the ionic potential. This is evidenced by a larger jump in the occupation number distribution.

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Short-range Coulomb correlations render massive Dirac fermions massless

Cited by 19 publications

References 29 publications

Semiconductor of spinons: from Ising band insulator to orthogonal band insulator

Semiconductor of spinons: from Ising band insulator to orthogonal band insulator

Effects of correlations on honeycomb lattice in ionic-Hubbard model

Quantum Integrability of 1D Ionic Hubbard Model

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