Midgap states of a two-dimensional antiferromagnetic Mott-insulator: Electronic structure of meron vortices

John, Sajeev; Berciu, Mona; Golubentsev, A. A.

doi:10.1209/epl/i1998-00111-0

Cited by 10 publications

(20 citation statements)

References 26 publications

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“…In this nontrivial magnetic structure the Mn and Fe magnetic moments rotate out of the surface plane, around the central Mn site, in a "lotus flower"-like spin configuration that resembles a half-skyrmion, i.e., a meron, topological object. 49,56 It is interesting to note that Heinze et al 57 have reported the existence of a two-dimensional square lattice of skyrmions as the magnetic ground state of an Fe film on Ir(111) surface. The microscopic origin has been explained in terms of a complex interplay between exchange interactions of various orders and Dzyaloshinskii-Moriya interactions.…”

Section: B Mn Nanostructures On Fe(001)mentioning

confidence: 99%

First-principles studies of complex magnetism in Mn nanostructures on the Fe(001) surface

et al. 2012

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The magnetic properties of Mn nanostructures on the Fe(001) surface have been studied using the noncollinear first-principles real space-linear muffin-tin orbital-atomic sphere approximation method within density-functional theory. We have considered a variety of nanostructures such as adsorbed wires, pyramids, and flat and intermixed clusters of sizes varying from two to nine atoms. Our calculations of interatomic exchange interactions reveal the long-range nature of exchange interactions between Mn-Mn and Mn-Fe atoms. We have found that the strong dependence of these interactions on the local environment, the magnetic frustration, and the effect of spin-orbit coupling lead to the possibility of realizing complex noncollinear magnetic structures such as helical spin spiral and half-skyrmion.

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Section: B Mn Nanostructures On Fe(001)mentioning

confidence: 99%

First-principles studies of complex magnetism in Mn nanostructures on the Fe(001) surface

et al. 2012

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“…As a result, the 2D HF equation reduces trivially to a 1D radial equation, with a structure very similar to that of the 1D differential HF equation obtained for the 1D Hubbard model. 17,18 Once this radial 1D solution is found, the 2D configuration is simply generated through a 2π rotation about an axis perpendicular to the 2D plane. As a result, there is a close analogy between solutions obtained for the 1D Hubbard model and for the 2D spin-flux model, in all our investigations.…”

Section: Doping Induced Meron-vortex Solitonsmentioning

confidence: 99%

“…An argument based on the electronic structure, identical to the one offered for the charged bosonic domain-walls of the polyacetylene, also holds. 17,18,14,20 The parallel to the quasi-one dimensional 1D polyacetylene is again a reflection of azimuthal symmetry which reduces the 2D continuum model to a 1D radial equation. Clearly, the isotropic dispersion about the Fermi points is responsible for the appearance of bosonic charge carriers.…”

Section: Doping Induced Meron-vortex Solitonsmentioning

confidence: 99%

“…The charged domain-wall traps the hole on a pair of levels that are localized deep inside the Mott-Hubbard gap, and is a charged boson. 17,18,10 The analog of the spinbag is the spin-polaron, which disturbs the AFM order only locally, trapping the hole in its small FM core. As a result, the spin-polaron carries both charge and spin− 1 2 .…”

mentioning

confidence: 99%

“…This mechanism is similar to the one leading to a broad mid-infrared absorption band in polyacetylene with doping. 29 (In the continuum limit, the meron vortex in fact creates a pair of mid-gap states in the Mott-Hubbard gap 17 ). The polyacetylene band is due to electronic excitations inside the cores of the polyacetylene domain-wall solitons, 20 which are the topological analogues of meron-vortices.…”

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A microscopic model for D-wave pairing in the cuprates: what happens when electrons somersault?

Berciu

John

2001

Physica B: Condensed Matter

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We present a microscopic model for a strongly repulsive electron gas on a 2D square lattice. We suggest that nearest neighbor Coulomb repulsion stabilizes a state in which electrons undergo a "somersault" in their internal spin-space (spin-flux). When this spin-1/2 antiferromagnetic (AFM) insulator is doped, the charge carriers nucleate mobile, charged, bosonic vortex solitons accompanied by unoccupied states deep inside the Mott-Hubbard charge-transfer gap. This model provides a unified microscopic basis for (i) non-Fermi-liquid transport properties, (ii) mid-infrared optical absorption, (iii) destruction of AFM long range order with doping, (iv) angled resolved spectroscopy (ARPES), and (v) d-wave preformed charged carrier pairs. We use the Configuration Interaction (CI) method to study the quantum translational and rotational properties of such pairs. The CI method systematically describes fluctuation and quantum tunneling corrections to the Hartree-Fock approximation and recaptures essential features of the (Bethe ansatz) exact solution of the Hubbard model in 1D. For a single hole in the 2D AFM plane, we find a precursor to spin-charge separation. The CI ground state consists of a bound vortex-antivortex pair, one vortex carrying the charge and the other one carrying the spin of the doping hole.

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Charged bosons in a doped Mott insulator: Electronic properties of domain-wall solitons and meron vortices

Berciu

John

1998

Phys. Rev. B

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We demonstrate from first principles that when a charge carrier is added to a spin-1/2 antiferromagnetic Mott insulator in either a one-or two-dimensional lattice, the self-consistent, Hartree-Fock ground state consists of a magnetic soliton texture with a doubly degenerate electronic level at the center of the Mott-Hubbard charge gap. This model is appropriate to systems with weak interchain or interlayer magnetic couplings in which long-range antiferromagnetic order is observed in the absence of charge carriers ͑doping͒. These magnetic solitons mediate the destruction of the magnetic order as the charge carrier concentration is increased. In a one-dimensional lattice with nearest-neighbor hopping t, on-site Coulomb repulsion U, and self-consistent, antiferromagnetic moment amplitude S, we find that a charged, fermionic, magnetic domain wall soliton with a weakly ferromagnetic core, centered between two sites, has lower Hartree-Fock energy than a corresponding charged quasiparticle in one of the Mott-Hubbard bands. However, for US/tϾ2, this soliton is unstable to the formation of a lower energy charged, bosonic domain wall soliton, centered on a single site. For US/tϽ 2, both of the above solitons are charged bosons. The self-consistent structure of these solitons exhibits no rotation of the local magnetic moments, but only a local suppression of the local moment amplitude in the vicinity of the hole. In the absence of doping, charge neutral domain wall solitons exhibit spin rotation within their core region. The equilibrium core size is determined by the degree of magnetic anisotropy. The ferromagnetic core soliton exhibits a pair of nondegenerate near-midgap electronic states. The antiferromagnetic core soliton exhibits a pair of nondegenerate electronic states that are symmetric about the midgap energy and that merge into the continuum as the anisotropy effects are made small and the soliton core radius becomes very large. The two-dimensional antiferromagnetic Mott insulator exhibits analogous behavior to the one-dimensional model. This analogy is precise for a 2D antiferromagnet exhibiting spin flux. For the undoped Mott insulator, the ferromagnetic core meron vortex ͑''lotus flower'' configuration of local magnetic moments͒ exhibits a doubly degenerate electronic midgap state in the continuum model and is the analog of the 1D neutral domain wall soliton. We demonstrate that a hole added to the 2D system can form a charged bosonic collective excitation, in which the spin background around the hole forms a planar vortex with local antiferromagnetic correlations at infinity and vanishing local-moment amplitude at the core of the soliton.

show abstract

Midgap states of a two-dimensional antiferromagnetic Mott-insulator: Electronic structure of meron vortices

Cited by 10 publications

References 26 publications

First-principles studies of complex magnetism in Mn nanostructures on the Fe(001) surface

First-principles studies of complex magnetism in Mn nanostructures on the Fe(001) surface

A microscopic model for D-wave pairing in the cuprates: what happens when electrons somersault?

Charged bosons in a doped Mott insulator: Electronic properties of domain-wall solitons and meron vortices

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