ELECTRONIC PROPERTIES OF GRAPHENE SYSTEMS UNDER TENSION
Pseudomagnetic field
External magnetic field
Graphene ring
Nanoribbon
Electronic properties
Nanoestrutura
Nanofita
Grafeno
Tensão
Campo magnético externo
Propriedade eletrônica
Tensão
Pseudocampo magnético
Campo magnético externo
Anel de grafeno
Nanofita
Propriedades eltrônicas
Faria, Daiara Fernandes de | Posted on:
2014
Abstract
We study the effects of strain on the electronic properties and persistent current characteristics of a graphene ring using the Dirac representation. For a slightly deformed
graphene ring flake, one obtains sizable pseudomagnetic (gauge) fields that may effectively reduce or enhance locally the applied magnetic flux through the ring. Flux-induced
persistent currents in a flat ring have full rotational symmetry throughout the structure;
in contrast, we show that currents in the presence of a circularly symmetric deformation
are strongly inhomogeneous, due to the underlying symmetries of graphene. This result
illustrates the inherent competition between the ‘real’ magnetic field and the ‘pseudo’ field
arising from strains, and suggests an alternative way to probe the strength and symmetries
of pseudomagnetic fields on graphene systems.
We also explored the transport properties of graphene systems (hexagonal zigzag rings
and the zigzag nanoribbons) coupled to left and right leads given by semi-infinite zigzag
nanoribbons, following the tight-binding approximation. The local and total density of
states and conductance are obtained following the Green’s function formalism and real
space renormalization techniques. The localization effects on the physical responses of
both system were considered as a consequence of the finite-size confnement of the central
part of the nanotructures and due to the applied magnetic field and the presence of tension
giving origin to pseudofields. For the nanoribbons we have focused on the apparent
regions exhibiting trigonal structure occuring due to a superposition of lattice and strain
symmetries. The zigzag hexagonal rings present very interesting transport properties
when a magnetic fux is considered. The conductance gets double-peaked at low energies,
and it is null at certain energy values, suggesting a possible destructive ring resonance.
The peculiar null conductance states are pinned at the same energy values independly of
the magnetic field intensity. We believe that strain is not able to destroy the constructive
and desctructive interference effects of the ring. We highlight that the strain also promotes
a change in the energy values in which the conductance is fully suppressed, being possible
to use the ring as a dispositive in which the conductance pattern, with open and close
modes, provides a simple way of measuring the strength of strain when compared to the
unstrained situation.
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Document type
TeseSubject(s)
StrainPseudomagnetic field
External magnetic field
Graphene ring
Nanoribbon
Electronic properties
Nanoestrutura
Nanofita
Grafeno
Tensão
Campo magnético externo
Propriedade eletrônica
Tensão
Pseudocampo magnético
Campo magnético externo
Anel de grafeno
Nanofita
Propriedades eltrônicas
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