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 strained folds can be engineered on graphene samples on appropriate substrates, we study their effects on graphene transport properties. We show the existence of an enhanced local density of states (LDOS) along the direction of the strained 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 these geometries viable electronic waveguides. These findings could be tested in properly engineered experimental settings.

Previous works on deformed graphene predict the existence of valley-polarized states, however, optimal conditions for their detection remain challenging. We show that in the quantum Hall regime, edge-like states in strained regions can be isolated in energy within Landau gaps. We identify precise conditions for new conducting edges-like states to be valley polarized, with the flexibility of positioning them at chosen locations in the system. A map of local density of states as a function of energy and position reveals a unique braid pattern that serves as a fingerprint to identify valley polarization.Strained graphene has emerged as an important tool to implement valleytronic based devices, and in particular, in protocols for quantum computation [1][2][3][4][5][6][7][8][9][10][11][12]. Recent experimental developments show that substrate engineering can be used to design deformation geometries with specific strain profiles [13][14][15][16][17][18][19][20][21][22][23]. Clear signatures of valley splitting in confined geometries represent an important step in this direction, as exemplified by STM studies on graphene quantum dots [24]. In more extended configurations, similar observations have been reported on multiple fold structures [18,19] with preliminary evidence of valley polarized states. These studies are supported by previous work on extended deformations predicting valley polarized edge-like states at the strain region, which acts as a waveguide focusing electron currents [1][2][3][4][5]. These are all promising structures for potential device applications. However, several drawbacks are still present because optimal conditions for creation and detection of valley split currents are not well-defined.To take advantage of the existence of valley polarized channels, usually embedded in graphene's conducting background, it is crucial to separate their contribution from other extended states. We show that this can be achieved by introducing an external magnetic field large enough to take the system into the Quantum Hall regime. Such a configuration conveniently allows the isolation of the valley polarized edge states in energy and in real space. As we show below, it is possible to design configurations within available experimental capabilities to produce valley polarized currents for a wide energy range within Landau gaps. Moreover, the flexibility to place the deformation at different parts of the sample provides a wider versatility of contact probes to identify and collect these currents.We present local density of states (LDOS) results for a model of graphene with a fold-like deformation that predict valley split peaks that could be measured in STM experiments. As the deformed region is traversed across, maximum LDOS intensities for each valley evolve in en-ergy, leading to a braid structure that serves as a unique fingerprint of valley polarized states. Under bias, these states generate new extra conducting channels that can be visualized as new edge states created along the deformation region.In order to ...

We analyze the electronic properties of a hybrid graphene-BN nanoribbon system, using a Hubbard model Hamiltonian within a mean field approximation. Due to the different electronegativities of the boron and nitrogen atoms, an electric field is induced across the zigzag graphene strip, breaking the spin degeneracy of the electronic band structure. Optimal tight-binding parameters are found from first-principles calculations. Edge potentials are proposed as corrections for the on-site energies, modeling the BN-graphene nanoribbon interfaces. We show that half-metallic responses in the hybrid systems may be driven with the help of an external electric field. We also study the role of defects across the graphene nanoribbon and at the h-BN/graphene interface regions. Modulations on the spin-dependent gaps may be achieved depending on the nature and position of the defect, constituting a way towards spin-gap engineering by means of spatial doping.

Strain fold-like deformations on armchair graphene nanoribbons (AGNRs) can be properly engineered in experimental setups, and could lead to a new controlling tool for gaps and transport properties. Here, we analyze the electronic properties of folded AGNRs relating the electronic responses and the mechanical deformation. An important and universal parameter for the gap engineering is the ribbon percent width variation, i.e., the difference between the deformed and undeformed ribbon widths. AGNRs bandgap can be tuned mechanically in a well defined bounded range of energy values, eventually leading to a metallic system. This characteristic provides a new controllable degree of freedom that allows manipulation of electronic currents. We show that the numerical results are analytically predicted by solving the Dirac equation for the strained system.

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