Energy Gap Induced by Friedel Oscillations Manifested as Transport Asymmetry at Monolayer-Bilayer Graphene Boundaries

Clark, Kendal; Zhang, X.-G.; Gu, Gong; Park, Jewook; He, Guowei; Feenstra, R. M.; Li, An‐Ping

doi:10.1103/physrevx.4.011021

Cited by 47 publications

(48 citation statements)

References 49 publications

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“…To investigate current on the nanoscale, recent experiments have realized multiple STM systems [15,16,74,75]. These allow for individual manipulation of several STM tips in order to make electrical contact to the sample near the considered nanostructure.…”

Section: Vortex Currents Near Perforationsmentioning

confidence: 99%

Patched Green's function techniques for two-dimensional systems: Electronic behavior of bubbles and perforations in graphene

et al. 2015

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We present a numerically efficient technique to evaluate the Green's function for extended two dimensional systems without relying on periodic boundary conditions. Different regions of interest, or 'patches', are connected using self energy terms which encode the information of the extended parts of the system. The calculation scheme uses a combination of analytic expressions for the Green's function of infinite pristine systems and an adaptive recursive Green's function technique for the patches. The method allows for an efficient calculation of both local electronic and transport properties, as well as the inclusion of multiple probes in arbitrary geometries embedded in extended samples. We apply the Patched Green's function method to evaluate the local densities of states and transmission properties of graphene systems with two kinds of deviations from the pristine structure: bubbles and perforations with characteristic dimensions of the order of 10-25 nm, i.e. including hundreds of thousands of atoms. The strain field induced by a bubble is treated beyond an effective Dirac model, and we demonstrate the existence of both Friedel-type oscillations arising from the edges of the bubble, as well as pseudo-Landau levels related to the pseudomagnetic field induced by the nonuniform strain. Secondly, we compute the transport properties of a large perforation with atomic positions extracted from a TEM image, and show that current vortices may form near the zigzag segments of the perforation.

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Section: Vortex Currents Near Perforationsmentioning

confidence: 99%

Patched Green's function techniques for two-dimensional systems: Electronic behavior of bubbles and perforations in graphene

et al. 2015

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“…The first method is based on locally gated graphene monolayer or bilayer, where local gates are used to individually control carrier densities and/or carrier types in two adjacent regions [1][2][3][4][5][6]8,9 , thus creating different QH states with different filling factors in a magnetic field. The second one is to use graphene monolayer and bilayer hybrid planar structures 7,[10][11][12] , where two adjacent regions with different QH states exist naturally because of the different Landau level sequences in the monolayer [13][14][15][16] and bilayer [17][18][19] regions. The atomically well-defined interface of the graphene monolayer-bilayer planar junction, which is fixed at the edge of the bilayer lattice, provides unprecedented opportunity to spatially explore the electronic properties of the interface in the QH regime.…”

mentioning

confidence: 99%

Spatially resolving unconventional interface Landau quantization in a graphene monolayer-bilayer planar junction

Yan

Yin

et al. 2016

Phys. Rev. B

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Graphene hybrid planar structures consisting of two regions with different quantum Hall (QH) states exhibit unusual transport properties 1-5 , originating from chiral edge states equilibration at the interface of the two different regions 6 . Here we present a sub-nanometre-resolved scanning tunnelling microscopy (STM) and spectroscopy (STS) study of a monolayer-bilayer graphene planar junction in the QH regime. The atomically well-defined interface of such a junction allows us to spatially resolve the interface electronic properties. Around the interface, we detect Landau quantization of massless Dirac fermions, as expected in graphene monolayer, below the charge neutrality point N c of the junction, whereas unexpectedly, only Landau quantization of massive Dirac fermions, as expected in graphene bilayer, is observed above the N c . The observed unconventional interface Landau quantization arises from the fact that the quantum conductance across the interface is solely determined by the minimum filling factors (number of edge modes) in the graphene monolayer and bilayer regions of the junction 6,7 .

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“…Compared to the conventional single-STM * mikse@nanotech.dtu.dk setups, which reflect local properties, the multiprobe signal provides additional information being a transport quantity. Multiprobe measurements have been used to characterize several systems: anisotropic transport [32], nanowires [24,33], carbon nanotubes [34], graphene nanoribbons [31], grain boundaries both in graphene [35,36] and other materials [37], and monolayer and bilayer graphene [38][39][40].…”

Section: Introductionmentioning

confidence: 99%

Dual-probe spectroscopic fingerprints of defects in graphene

et al. 2014

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Recent advances in experimental techniques emphasize the usefulness of multiple scanning probe techniques when analyzing nanoscale samples. Here, we analyze theoretically dual-probe setups with probe separations in the nanometer range, i.e., in a regime where quantum coherence effects can be observed at low temperatures. In a dual-probe setup the electrons are injected at one probe and collected at the other. The measured conductance reflects the local transport properties on the nanoscale, thereby yielding information complementary to that obtained with a standard one-probe setup (the local density of states). In this work we develop a real-space Green's function method to compute the conductance. This requires an extension of the standard calculation schemes, which typically address a finite sample between the probes. In contrast, the developed method makes no assumption of the sample size (e.g., an extended graphene sheet). Applying this method, we study the transport anisotropies in pristine graphene sheets, and analyze the spectroscopic fingerprints arising from quantum interference around single-site defects, such as vacancies and adatoms. Furthermore, we demonstrate that the dual-probe setup is a useful tool for characterizing the electronic transport properties of extended defects or designed nanostructures. In particular, we show that nanoscale perforations, or antidots, in a graphene sheet display Fano-type resonances with a strong dependence on the edge geometry of the perforation.

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Energy Gap Induced by Friedel Oscillations Manifested as Transport Asymmetry at Monolayer-Bilayer Graphene Boundaries

Cited by 47 publications

References 49 publications

Patched Green's function techniques for two-dimensional systems: Electronic behavior of bubbles and perforations in graphene

Patched Green's function techniques for two-dimensional systems: Electronic behavior of bubbles and perforations in graphene

Spatially resolving unconventional interface Landau quantization in a graphene monolayer-bilayer planar junction

Dual-probe spectroscopic fingerprints of defects in graphene

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