Autómatas finitos: irreducibilidad e Inferencia.

Andrade, Manuel Vázquez de Parga

doi:10.4995/thesis/10251/2321

Cited by 3 publications

(3 citation statements)

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“…In contrast, bottom-up processing of graphene nanoislands is very promising [18]. Hexagonal shape nanoislands with well-defined zigzag edges atop the 0001 surface of Ru have already been achieved [19]. This experimental progress motivates our study of the electronic structure of graphene nanostructures with various shapes.…”

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confidence: 99%

Magnetism in Graphene Nanoislands

2007

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We study the magnetic properties of nanometer-sized graphene structures with triangular and hexagonal shapes terminated by zigzag edges. We discuss how the shape of the island, the imbalance in the number of atoms belonging to the two graphene sublattices, the existence of zero-energy states, and the total and local magnetic moment are intimately related. We consider electronic interactions both in a mean-field approximation of the one-orbital Hubbard model and with density functional calculations. Both descriptions yield values for the ground state total spin S consistent with Lieb's theorem for bipartite lattices. Triangles have a finite S for all sizes whereas hexagons have S 0 and develop local moments above a critical size of 1:5 nm. DOI: 10.1103/PhysRevLett.99.177204 PACS numbers: 75.75.+a, 73.20.ÿr, 75.50.Xx, 75.70.Cn The study of graphene-based field effect devices has opened a new research venue in nanoelectronics [1][2][3][4][5]. Graphene is a truly two-dimensional zero-gap semiconductor with peculiar transport and magnetotransport propreties, including the room temperatrue quantum Hall effect [6], that makes it very different from conventional semiconductors and metals [7]. Progress in the fabrication of graphene-based lower dimensional structures has been reported both in the form of one-dimensional ribbons [8,9] and zero-dimensional dots [2,7,10]. Interestingly, the electronic properties of graphene change in a nontrivial manner when going to lower dimensions. Ribbons, for instance, can be either semiconducting with a size dependent gap or metallic [8,9].The electronic structure of graphene-based nanostructures is expected to be different from bulk graphene because of surface, or, more properly, edge effects [11]. This is particularly true in the case of structures with zizzag edges which present magnetic properties [12 -14]. Whereas bulk graphene is a diamagnetic semimetal, simple tight-binding models predict that one-dimensional ribbons with zigzag edges have two flat bands at the Fermi energy [11,12,[15][16][17], i.e., are paramagnetic metals. Spin polarized density functional theory (DFT) [13] and mean-field [12] calculations confirm that these bands are prone to magnetic instabilities.The fabrication of graphene nanostructures using topbottom techniques does not permit creating atomically defined edges to date [10]. In contrast, bottom-up processing of graphene nanoislands is very promising [18]. Hexagonal shape nanoislands with well-defined zigzag edges atop the 0001 surface of Ru have already been achieved [19]. This experimental progress motivates our study of the electronic structure of graphene nanostructures with various shapes. Graphene quantum dots also hold the promise of extremely long spin relaxation and decoherence time because of the very small spin-orbit and hyperfine coupling in carbon [20].We have found that, remarkably, both the DFT calculations and the mean-field approximation of the single-band Hubbard model with first-neighbors hopping yield very similar results in all c...

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confidence: 99%

Magnetism in Graphene Nanoislands

2007

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“…In contrast, bottom-up processing of graphene nano-islands is very promising 19 . Hexagonal shape nano-islands with well-defined zigzag edges atop the 0001 surface of Ru have already been achieved 20 . This experimental progress motivates our study of the electronic structure of graphene nanostructures with various shapes.…”

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confidence: 98%

Magnetism in graphene nano-islands

Fernandez-Rossier,

Palacios

2007

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“…6. Las ediciones manejadas son las siguientes: -Vitas Sanctorum Patrum Emeritensium (VPE): MAYA SÁNCHEZ, 1992; -Vitae Sancti Aemiliani (VSE): VÁZQUEZ DE PARGA, 1943;OROZ, 1978;escritos de Valerio del Bierzo:AHERNE, 1949;-Vita Fructuosi: DÍAZ Y DÍAZ, 1974.Véase una síntesis sobre la hagiografía hispanovisigoda en DÍAZ Y DÍAZ, 1981. 7. Sobre el patrimonio de la iglesia emeritense vid.…”

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Conflictos entre la autoridad y el "hombre santo" : hacia el control oficial del "patronatus caelestis" en la Hispania Visigoda

Castellanos

1996

Brocar

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La capitalización episcopal del culto de los santos es un fenómeno bien conocido durante la antigüedad tardía. Sin embargo, existieron algunos conflictos especialmente "en vida" de los "hombres santos". Este artículo trata de mostrar los principales casos en la hispania visigoda: "el hombre santo" aparece en ocasiones enfrentado a la autoridad (reyes y obispos). En cualquier caso, el "patronatus caelestis" terminara en buena parte bajo el control de los grupos dirigentes. Interesa aquí únicamente el conflicto "en vida" del "hombre santo" como paso inicial en el proceso de capitalización.

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Autómatas finitos: irreducibilidad e Inferencia.

Cited by 3 publications

References 25 publications

Magnetism in Graphene Nanoislands

Magnetism in Graphene Nanoislands

Magnetism in graphene nano-islands

Conflictos entre la autoridad y el "hombre santo" : hacia el control oficial del "patronatus caelestis" en la Hispania Visigoda

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