We study the effects of strain on the electronic properties and persistent current characteristic... more 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.
In order to investigate measurable strain signatures on graphene, we focus on scattering properti... more In order to investigate measurable strain signatures on graphene, we focus on scattering properties of an infinite graphene sheet with a single centro-symmetric out-of-plane deformation. Open systems offer the advantage that issues concerning to specific boundary conditions are avoided. A perturbative approach is used in the continuum limit for small deformations to obtain the local density of states (LDOS) and results are compared with a Dirac model solved by iterative scattering matrix methods. Real space imaging reveals a characteristic six-fold symmetry pattern with sublattice symmetry breaking within each fold, consistent with experimental and tight-binding observations. We also provide an analytical expression for the contrast between the local density of states of each sub-lattice in each fold for the case of a Gaussian deformation, showing a scaling law as a function of the amplitude and width of the deformation.
We study transport properties of hexagonal zigzag graphene quantum rings connected to
semi-infini... more We study transport properties of hexagonal zigzag graphene quantum rings connected to semi-infinite nanoribbons. Open two-fold symmetric structures support localized states that can be traced back to those existing in the isolated six-fold symmetric rings. Using a tight-binding Hamiltonian within the Green’s function formalism, we show that an external magnetic field promotes these localized states to Fano resonances with robust signatures in transport. Local density of states and current distributions of the resonant states are calculated as a function of the magnetic flux intensity. For structures on corrugated substrates we analyze the effect of strain by including an out-of-plane centro-symmetric deformation in the model. We show that small strains shift the resonance positions without further modifications, while high strains introduce new ones.
The coupling of geometrical and electronic properties is a promising venue to engineer conduction... more The coupling of geometrical and electronic properties is a promising venue to engineer conduction
properties in graphene. Confinement added to strain allows for interplay of different transport mechanisms
with potential device applications. To investigate strain signatures on transport in confined geometries, we
focus on graphene nanoribbons (GNRs) with circularly symmetric deformations. In particular, we study
GNRs with an inhomogeneous out-of-plane Gaussian deformation, connected to reservoirs. We observe an
enhancement of the density of states in the deformed region, accompanied with a decrease in the conductance,
signaling the presence of confined states. The local density of states exhibits a sixfold symmetric structure
with an oscillating sublattice occupation asymmetry that persists for a wide range of energy and model
parameters.
Deformations in graphene systems are central elements in the novel field of straintronics. Variou... more Deformations in graphene systems are central elements in the novel field of straintronics. Various strain geometries have been proposed to produce specific properties but their experimental realization has been limited. Because folds occur naturally in graphene samples, or could be engineered with appropriate substrates, we study their effects on graphene transport properties. We show the existence of an enhanced local density of states (LDOS) along the fold that originates from localization of higher energy states, and provides extra conductance channels at lower energies. In addition to exhibit sublattice symmetry breaking, these states are valley polarized, with quasi-ballistic properties in smooth disorder potentials. We confirmed that these results persist in the presence of strong edge disorder, making folds viable electronic waveguides. These findings could be tested in currently available experimental settings.
We study the effects of strain on the electronic properties and persistent current characteristic... more 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.
In order to investigate measurable strain signatures on graphene, we focus on scattering properti... more In order to investigate measurable strain signatures on graphene, we focus on scattering properties of an infinite graphene sheet with a single centro-symmetric out-of-plane deformation. Open systems offer the advantage that issues concerning to specific boundary conditions are avoided. A perturbative approach is used in the continuum limit for small deformations to obtain the local density of states (LDOS) and results are compared with a Dirac model solved by iterative scattering matrix methods. Real space imaging reveals a characteristic six-fold symmetry pattern with sublattice symmetry breaking within each fold, consistent with experimental and tight-binding observations. We also provide an analytical expression for the contrast between the local density of states of each sub-lattice in each fold for the case of a Gaussian deformation, showing a scaling law as a function of the amplitude and width of the deformation.
We study transport properties of hexagonal zigzag graphene quantum rings connected to
semi-infini... more We study transport properties of hexagonal zigzag graphene quantum rings connected to semi-infinite nanoribbons. Open two-fold symmetric structures support localized states that can be traced back to those existing in the isolated six-fold symmetric rings. Using a tight-binding Hamiltonian within the Green’s function formalism, we show that an external magnetic field promotes these localized states to Fano resonances with robust signatures in transport. Local density of states and current distributions of the resonant states are calculated as a function of the magnetic flux intensity. For structures on corrugated substrates we analyze the effect of strain by including an out-of-plane centro-symmetric deformation in the model. We show that small strains shift the resonance positions without further modifications, while high strains introduce new ones.
The coupling of geometrical and electronic properties is a promising venue to engineer conduction... more The coupling of geometrical and electronic properties is a promising venue to engineer conduction
properties in graphene. Confinement added to strain allows for interplay of different transport mechanisms
with potential device applications. To investigate strain signatures on transport in confined geometries, we
focus on graphene nanoribbons (GNRs) with circularly symmetric deformations. In particular, we study
GNRs with an inhomogeneous out-of-plane Gaussian deformation, connected to reservoirs. We observe an
enhancement of the density of states in the deformed region, accompanied with a decrease in the conductance,
signaling the presence of confined states. The local density of states exhibits a sixfold symmetric structure
with an oscillating sublattice occupation asymmetry that persists for a wide range of energy and model
parameters.
Deformations in graphene systems are central elements in the novel field of straintronics. Variou... more Deformations in graphene systems are central elements in the novel field of straintronics. Various strain geometries have been proposed to produce specific properties but their experimental realization has been limited. Because folds occur naturally in graphene samples, or could be engineered with appropriate substrates, we study their effects on graphene transport properties. We show the existence of an enhanced local density of states (LDOS) along the fold that originates from localization of higher energy states, and provides extra conductance channels at lower energies. In addition to exhibit sublattice symmetry breaking, these states are valley polarized, with quasi-ballistic properties in smooth disorder potentials. We confirmed that these results persist in the presence of strong edge disorder, making folds viable electronic waveguides. These findings could be tested in currently available experimental settings.
Uploads
Papers by Daiara Faria
semi-infinite nanoribbons. Open two-fold symmetric structures support localized states that
can be traced back to those existing in the isolated six-fold symmetric rings. Using a
tight-binding Hamiltonian within the Green’s function formalism, we show that an external
magnetic field promotes these localized states to Fano resonances with robust signatures in
transport. Local density of states and current distributions of the resonant states are calculated
as a function of the magnetic flux intensity. For structures on corrugated substrates we analyze
the effect of strain by including an out-of-plane centro-symmetric deformation in the model.
We show that small strains shift the resonance positions without further modifications, while
high strains introduce new ones.
properties in graphene. Confinement added to strain allows for interplay of different transport mechanisms
with potential device applications. To investigate strain signatures on transport in confined geometries, we
focus on graphene nanoribbons (GNRs) with circularly symmetric deformations. In particular, we study
GNRs with an inhomogeneous out-of-plane Gaussian deformation, connected to reservoirs. We observe an
enhancement of the density of states in the deformed region, accompanied with a decrease in the conductance,
signaling the presence of confined states. The local density of states exhibits a sixfold symmetric structure
with an oscillating sublattice occupation asymmetry that persists for a wide range of energy and model
parameters.
Drafts by Daiara Faria
semi-infinite nanoribbons. Open two-fold symmetric structures support localized states that
can be traced back to those existing in the isolated six-fold symmetric rings. Using a
tight-binding Hamiltonian within the Green’s function formalism, we show that an external
magnetic field promotes these localized states to Fano resonances with robust signatures in
transport. Local density of states and current distributions of the resonant states are calculated
as a function of the magnetic flux intensity. For structures on corrugated substrates we analyze
the effect of strain by including an out-of-plane centro-symmetric deformation in the model.
We show that small strains shift the resonance positions without further modifications, while
high strains introduce new ones.
properties in graphene. Confinement added to strain allows for interplay of different transport mechanisms
with potential device applications. To investigate strain signatures on transport in confined geometries, we
focus on graphene nanoribbons (GNRs) with circularly symmetric deformations. In particular, we study
GNRs with an inhomogeneous out-of-plane Gaussian deformation, connected to reservoirs. We observe an
enhancement of the density of states in the deformed region, accompanied with a decrease in the conductance,
signaling the presence of confined states. The local density of states exhibits a sixfold symmetric structure
with an oscillating sublattice occupation asymmetry that persists for a wide range of energy and model
parameters.