Magnetism in graphene nano-islands

Fernandez-Rossier, J.; Palacios, J. J.

doi:10.48550/arxiv.0707.2964

Cited by 2 publications

(4 citation statements)

References 17 publications

(27 reference statements)

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“…The reduced dimension of these quantum dots introduces important physical phenomena such as quantum confinement and edge effects. 10,17,18,19,20,21,22,23 Several theoretical studies have emphasized the importance of such effects when considering the electronic structure, 24,25,26,27,28 electric transport, 29,30,31,32,33 and magnetic 34,35,36 properties of finite carbon nanotubes (CNTs). These effects are expected to be manifested in experiments involving the dielectric screening constants, 26 optical excitations 37 and Raman spectrum 38 of such systems.…”

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confidence: 99%

Edge effects in finite elongated graphene nanoribbons

2007

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We analyze the relevance of finite-size effects to the electronic structure of long graphene nanoribbons using a divide and conquer density functional approach. We find that for hydrogen terminated graphene nanoribbons most of the physical features appearing in the density of states of an infinite graphene nanoribbon are recovered at a length of 40 nm. Nevertheless, even for the longest systems considered (72 nm long) pronounced edge effects appear in the vicinity of the Fermi energy. The weight of these edge states scales inversely with the length of the ribbon and they are expected to become negligible only at ribbons lengths of the order of micrometers. Our results indicate that careful consideration of finite-size and edge effects should be applied when designing new nanoelectronic devices based on graphene nanoribbons. These conclusions are expected to hold for other one-dimensional systems such as carbon nanotubes, conducting polymers, and DNA molecules.Graphene nanoribbons (GNRs) have been suggested as potential candidates for replacing electronic components and interconnects in future nanoelectronic 1,2,3,4,5,6,7 and nanospintronic 8,9,10 devices. Experiments have revealed the possibility of obtaining a wide range of electronic behavior when studying these systems, ranging from coherent transport 11 suitable for interconnects, to field effect switching capabilities 12 needed for electronic components design. While many transport experiments involve long segments of GNRs 1,11,13,14 , recent developments have allowed the fabrication of graphene based quantum dots 5,7,15,16 . The reduced dimension of these quantum dots introduces important physical phenomena such as quantum confinement and edge effects. 10,17,18,19,20,21,22,23 Several theoretical studies have emphasized the importance of such effects when considering the electronic structure, 24,25,26,27,28 electric transport, 29,30,31,32,33 and magnetic 34,35,36 properties of finite carbon nanotubes (CNTs). These effects are expected to be manifested in experiments involving the dielectric screening constants, 26 optical excitations 37 and Raman spectrum 38 of such systems. Similar to CNTs it is predicted that the physical characteristics of finite GNRs may be considerably different from those of their infinite counterparts. Therefore, it is essential to identify the limit at which finite-size effects have to be taken into account. An important question therefore arises: what is the length at which a finite GNR becomes indistinguishable from its infinite counterpart?The purpose of this Letter is to provide a quantitative answer to this question based on first-principles calculations. To this end, we employ density functional theory (DFT) to study the electronic structure of hydrogen terminated GNRs as a function of their length, up to 72 nm. Finite-size effects are studied using a divide and conquer approach for first-principles electronic structure and transport calculations through finite elongated systems. 39 A careful comparison with the electronic st...

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Edge effects in finite elongated graphene nanoribbons

2007

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“…Chemical doping of the ribbon edges was shown to enhance this effect resulting in an efficient and robust spin filter device. 21 Following these studies on the half-metallic nature of one-dimensional zigzag graphene nanoribbons, several papers on the electronic properties, 22 magnetic properties 23,24,25,26 and the half-metallic nature 27,28 of quasi-zero-dimensional graphene-based structures have appeared. These concluded that the spin polarized character of the zigzag graphene edges persists also in nanometer scale islands of graphene, and that the halfmetallic nature of the structures studied by Son et al 9 may be an artifact of the level of theory they applied.…”

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“…Given that most organic molecules are known to be diamagnetic, while periodic 3,4,5,6,7,8,9,21 and finite graphene clusters 23,24,25,27 are predicted to have a spin polarized ground state, we begin by studying the emer-gence of magnetic ordering in ultra-short and ultranarrow rectangular graphene nanoribbons. In panels (a)-(e) of Fig.…”

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confidence: 99%

“…All the structures studied have compensated lattices in the sense that the number of carbon atoms belonging to each graphene sub-lattice are balanced. Therefore, according to Lieb's theorem for bipartite lattices 25,55 they have no total spin moment. The two smallest structures that present magnetic ordering in their ground state are found to be the Phenanthro[1,10,9,8-opqra]perylene (bisanthrene) isomer of the C 28 H 14 molecule and the Tetrabenzo[bc,ef,kl,no]coronene isomer of the C 36 H 16 molecule.…”

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Half-metallic graphene nanodots

Hod,

Barone,

Scuseria

2007

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A comprehensive first-principles theoretical study of the electronic properties and half-metallic nature of finite rectangular graphene nanoribbons is presented. We identify the bisanthrene isomer of the C28H14 molecule to be the smallest polycyclic aromatic hydrocarbon to present a spin polarized ground state. Even at this quantum dot level, the spins are predicted to be aligned antiferromagnetically at the two zigzag edges of the molecule. As a rule of thumb, we find that zigzag edges that are at least three consecutive units long, will present spin polarization if the width of the system is 1 nm or wider. Room temperature detectability of the magnetic ordering is predicted for molecules with zigzag edges 1 nm and longer. For the longer systems studied, spin wave structures appear in some high spin multiplicity states. Energy gap oscillations with the length of the zigzag edge are observed. The amplitude of these oscillations is found to be smaller than that predicted for infinite ribbons. The half-metallic nature of the ribbons under an external in-plane electric field is found to be preserved even for finite and extremely short systems.

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Magnetism in graphene nano-islands

Cited by 2 publications

References 17 publications

Edge effects in finite elongated graphene nanoribbons

Edge effects in finite elongated graphene nanoribbons

Half-metallic graphene nanodots

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