Transport through graphenelike flakes with intrinsic spin-orbit interactions

2018

Acta Phys. Pol. A

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This study shows that magnetic edge states of graphene-like nanoribbons enhance effectively the thermoelectric performance. This is due to the antiparallel alignment of magnetic moments on opposite zigzag edges and the confinement effect, which jointly lead to the appearance of a gap in the electronic energy spectrum. Consequently, the Seebeck coefficient as well as the thermoelectric power factor get strongly enhanced (with respect to other alignment cases) at room temperature and energies not far away from the charge neutrality point. Moreover the corresponding figure of merit (ZT) is also improved as a result of the reduced electronic thermal conductance.

Section: Discussion Of the Resultsmentioning

confidence: 73%

“…The model which has been proved to provide a good description of graphene-like nanostructures reads as follows (see [3,4] and references therein)…”

Section: Methodsmentioning

confidence: 99%

Effect of Magnetic Zigzag Edges in Graphene-like Nanoribbons on the Thermoelectric Power Factor

2018

Acta Phys. Pol. A

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“…Theoretical studies of graphenelike nanoribbons are usually carried out for the out-of-plane configuration [18 and 19], but it is now known that the in-plane configuration is often energetically the most stable one [20][21][22]. Here most of our attention is directed to this very configuration which constitutes the ground state for energies close to the charge neutrality point (CNP).…”

Section: Electronic Band Structure and Edge Magnetic Momentsmentioning

confidence: 99%

Edge magnetism impact on electrical conductance and thermoelectric properties of graphenelike nanoribbons

2017

Phys. Rev. B

Edge states in narrow quasi two-dimensional nanostructures determine, to a large extent, their electric, thermoelectric and magnetic properties. Non-magnetic edge states may quite often lead to topological insulator type behavior. However another scenario develops when the zigzag edges are magnetic and the time reversal symmetry is broken. In this work we report on the electronic band structure modifications, electrical conductance and thermoelectric properties of narrow zigzag nanoribbons with spontaneously magnetized edges. Theoretical studies based on the Kane-Mele-Hubbard tight-binding model show that for silicene, germanene and stanene both the Seebeck coefficient and the thermoelectric power factor are strongly enhanced for energies close to the charge neutrality point. Perpendicular gate voltage lifts the spin degeneracy of energy bands in the ground state with antiparallel magnetized zigzag edges and makes the electrical conductance significantly spin-polarized. Simultaneously the gate voltage worsens the thermoelectric performance. Estimated room-temperature figures of merit for the aforementioned nanoribbons can exceed a value of 3 if phonon thermal conductances are adequately reduced.

“…The problem is exactly solved by a direct diagonalization of the full Hamiltonian (cf. [5,6]). Figure 1 shows a distribution of magnetic moments in a small rectangular GLNR composed of W ac = 6 zigzag lines (width),and L zz = 8 blunt saw-teeth lines (length), the last line is incomplete for symmetry reasons.…”

Section: Methodsmentioning

confidence: 99%

“…Unlike graphene, they usually have sufficiently large intrinsic spin-orbit interaction which strongly impacts their electronic and magnetic properties [1][2][3]. It is now known that zigzag-shaped edges of graphene and graphene-like nanoribbons (GLNRs) may have noticeable magnetic moments, and their ground state configuration corresponds to the in-plane spin arrangement rather than the out-of-plane one [4,5]. The aim of this study is to estimate the effect of both ISOI and perpendicular external electric field on energy gaps and edge magnetic moments of GLNR.…”

Section: Introductionmentioning

confidence: 99%

In-Plane Edge Magnetism in Graphene-Like Nanoribbons

2017

Acta Phys. Pol. A

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This paper is devoted to identification of the most important factors responsible for formation of magnetic moments at edges of graphene-like nanoribbons. The main role is attributed to the Hubbard correlations (within unrestricted Hartree-Fock approximation) and intrinsic spin-orbit interactions, but additionally a perpendicular electric field is also taken into account. Of particular interest is the interplay of the in-plane edge magnetism and the energy band gap. It is shown that, with the increasing electric field, typically the following phases develop: magnetic insulator (with in-plane spins), nonmagnetic narrow-band semiconductor, and nonmagnetic band insulator.