Ground state magnetic properties in AA-stacking bilayer graphene quantum dots using Lieb’s theorem

Sharifian, Mahmoodreza; Hoseini, S. S.; Faizabadi, Edris

doi:10.1016/j.jmmm.2019.01.057

Cited by 14 publications

(9 citation statements)

References 31 publications

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“…In graphene quantum dots, both mean-field approximation of the one-orbital Hubbard model and optimized density functional calculations have similar results, and they are consistent with Lieb's theorem for bipartite lattices [34,35]. Whereas, the presence of a lone pair orbital oriented out-of-plane of phosphorus atoms has deprived us of the possibility of this assessment.…”

Section: Unsaturated Structuressupporting

confidence: 61%

“…As one can see, pre-TZMPQD, pre-TAMPQD, and TZM-PQD are ferromagnetic structures with total magnetic moment 6μ B , 8μ B , and 4μ B , respectively; by contrast, TAMPQD has an anti-ferromagnetic behavior with total spin S = 0. Like ferromagnetic triangular graphene quantum dots [34,35], the total net spin is mostly sitting on the edge, and local magnetization goes to zero in the center of the magnetic nanoflakes. Also, the schematic view of electron densities is illustrated in figures 2(e) and (f ).…”

Section: Unsaturated Structuresmentioning

confidence: 99%

“…As expected, local magnetization results produce a cluster of mid-gap states in the spectra corresponding to ferromagnetic quantum dots. It is of great importance to mention that these mid-gap states are empty of the electron, and therefore, the magnetic effect is relevant to the electronic states of half-filled orbitals closed to the highest occupied molecular orbital (HOMO); while in equivalent graphene structures, the magnetization property comes from zero-energy states [34,35]. By comparison of our DFT spin-resolved calculations with non-spin tight-binding approximation [25,26], we have found a relative similarity in their spectrums just for pre-optimized systems.…”

Section: Unsaturated Structuresmentioning

confidence: 99%

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Edge effects on the intrinsic magnetism in ferromagnetic triangular phosphorene quantum dots using fully spin-polarized calculations

Hoseini¹,

Faizabadi²

2021

J. Phys.: Condens. Matter

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This project involves discovering the electronic and magnetic properties of nanometer-sized phosphorene structures with triangular shapes in both zigzag and armchair termination types. The goal is to discuss the relationship between the electronic states belonging to the different conditions of these phosphorene quantum dots and their intrinsic magnetic properties. For this purpose, we consider electronic interactions utilizing the spin-polarized density functional theory calculations, and then the results compare with the data generated from tight-binding calculations. Both descriptions yield mid-gap states in the spectrum of ferromagnetic structures. Our results in non-spin computations without any geometry optimization were matched by tight-binding calculations which shows that the tight-binding method is an inefficient approximation in analyzing the optimized spin samples. Unlike graphene, in our spin-polarized calculations, we have obtained empty mid-gap states in the spectrum of ferromagnetic triangular phosphorene quantum dots. The edge atoms of these structures are known as the magnetic atoms with an unequal contribution of spin up and spin down. To prevent deforming the initial structures, the dangling bonds at the edge atoms were passivated in two types, fully hydrogenated and partial passivation with oxygen atoms. Oxygen doping was required for introducing magnetism to the non-spin edges of the fully hydrogenated case.

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Section: Unsaturated Structuressupporting

confidence: 61%

Section: Unsaturated Structuresmentioning

confidence: 99%

Section: Unsaturated Structuresmentioning

confidence: 99%

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Edge effects on the intrinsic magnetism in ferromagnetic triangular phosphorene quantum dots using fully spin-polarized calculations

Hoseini¹,

Faizabadi²

2021

J. Phys.: Condens. Matter

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“…Furthermore, Figure 1a,b illustrate proposed sublattices in bowtie and AA‐BTG, respectively. [ 40 ] As can be seen, bowtie and AA‐TBG have compensated structures (

N_{normalA} = N_{normalB}

), suggesting an antiferromagnetic coupling or

S = 0

total spin. In the following, we compare a bowtie with AA‐BTG counterpart labeled by identical Q .…”

Section: Structurementioning

confidence: 98%

Antiferromagnetic Ordering in Bowtie and AA‐Stacking Bilayer Trapezoidal Graphene Nanoflakes: A Comparison Study

Khodadadi

Sharifian

2023

Physica Rapid Research Ltrs

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Herein, a comparative computational study inquiring about ground state magnetic properties of a nanometer‐size bowtie graphene quantum dot with an AA‐stacking bilayer trapezoid counterpart based on the single‐orbital Hubbard model and density functional theory (DFT) is presented. The structures have an antiferromagnetic ground state with a 1‐to‐1 correspondence between the local spin polarizations of the two systems. The tight‐binding energy spectra look different. However, a similar fashion in the energy spectra emerges after considering the Hubbard interaction term. A comparison between the spatial distributions of edge states shows that the wave functions in both structures are sublattice polarized by proposing a specific unit cell in the bilayer case. In addition, the on‐site coulombic repulsion consequence on the rising of magnetization and the size of the local magnetic moment has been considered.

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“…Such a strategy has been utilized effectively in late theoretical studies. [12,39] Furthermore, practical strategies for explaining the quantum spin-transport properties of defective zGNRs have been outlined using first-principle calculations and a Landauer-Buttiker approach so as to be able to make an assessment investigation between the model Hamiltonian and DFT calculations.…”

Section: Introductionmentioning

confidence: 99%

Impact of Topological Edge Defects on Spin Transport Properties of Zigzag Graphene Nanoribbons

Sharifian

Ghasemifard

Taghizade

et al. 2021

Physica Status Solidi (b)

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Herein, the spin‐dependent transport properties of a zigzag graphene nanoribbon (zGNR) with edges decorated with a fluoranthene group are studied. Atomically perfect zigzag edge, including phenyl‐edge functionalization, was synthesized by Ruffieux et al. in a bottom‐up chemical technique. By performing nearest‐neighbor tight‐binding model in combination with Landauer formalism and Green's function approach, as well as considering Coulomb electronic interaction computed both with density functional calculations and mean‐field approximation of the Hubbard model, the magnetic and spin‐resolved transmissions are studied. Both the model Hamiltonian and density functional theory (DFT) descriptions yield very similar results. Importantly, by generating a special supercell, three different antiferromagnetic alignments for phenyl‐edge zGNR have been calculated, which was not developed in previous studies. The results show that by adding pentagon rings on both sides of the zGNR, the conductance loses its step‐like behavior. Our structure of interest is a semiconductor with a transport gap of 0.56 eV. This kind of defective structure will enable the spin‐feature characteristic, such as spin filtering, and add the spin degree of freedom to graphene‐based logic devices.

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Ground state magnetic properties in AA-stacking bilayer graphene quantum dots using Lieb’s theorem

Cited by 14 publications

References 31 publications

Edge effects on the intrinsic magnetism in ferromagnetic triangular phosphorene quantum dots using fully spin-polarized calculations

Edge effects on the intrinsic magnetism in ferromagnetic triangular phosphorene quantum dots using fully spin-polarized calculations

Antiferromagnetic Ordering in Bowtie and AA‐Stacking Bilayer Trapezoidal Graphene Nanoflakes: A Comparison Study

Impact of Topological Edge Defects on Spin Transport Properties of Zigzag Graphene Nanoribbons

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