Quantum interference and klein tunnelling in graphene heterojunctions pdf

Wu y, perebeinos v, lin y m, low t, xia f and avouris p 2012 quantum behavior of graphene transistors near the scaling limit nano lett. Lowenergy electronic excitations in graphene can be. Jan 27, 2011 electron transport through short, phasecoherent metal graphene metal devices occurs via resonant transmission through particle in aboxlike states defined by the atomicallysharp metal leads. The observation of quantum conductance oscillations in mesoscopic systems has traditionally required the confinement of the carriers to a phase space of reduced dimensionality. In particular, they have unique properties that make. Quantum tunnelling is not predicted by the laws of classical mechanics where surmounting a potential barrier requires enough potential. Shot noise generated by graphene pn junctions in the quantum.

Towards graphenebased quantum interference devices j. Entanglement generation due to the klein tunneling in a. The results prove that grgaln with nitrogenvacancy grgalnvn is energy favorable with the smallest sublayer distance and binding energy. The consideration of interference effects is an integral part for the understanding of raman spectra from graphene sheets.

Graphene and relativistic quantum physics bourbaphy. Currentphase relation in graphene and application to a superconducting quantum interference device c. A crossover between weak localization and weak antilocalization effects is observed when varying the gate voltage and we discuss the underlying scattering mechanisms. Quantum theory of graphene graphenes electronic structure. The halfinteger quantum hall effect, and klein tunneling were demonstrated in electricaltransport measurements, and graphenebased supercurrent transistors, and spintronic devices. The klein paradox role of chirality klein tunneling in singlelayer graphene.

Kleintunneling transistor with ballistic graphene abstract references. If the mode mixing is quasielastic, f pnj e is a doublestep function. Neutrons reveal quantum tunnelling on graphene enables the. This cited by count includes citations to the following articles in scholar. Today, the availability of high mobility graphene up to room temperature makes ballistic transport in nanodevices achievable. Thus, the matrix representation of the hamiltonian defined on this lattice can be obtained in the same fashion as for the square lattice used in problem 4. We report an electrically tunable graphene quantum switch based on dirac fermion optics dfo, with electrostatically defined analogies of mirror and collimators utilizing angledependent klein tunneling. We show that the pn interface acts as a semitransparent mirror in the bipolar regime and that the reflectance and transmittance of the pn interface can be tuned by the gate voltages. A kleintunneling transistor with ballistic graphene iopscience. Quantum interference and klein tunneling in graphene. Quantum interference and klein tunneling in graphene heterojunctions. The lead states are electrostatically tuned by a global backgate, resulting in a distinct pattern of varying intensity in the measured conductance maps. Young and philip kim department of physics, columbia university, new york, new york 10027, usa dated.

When two dimensional crystals are atomically close, their finite thickness becomes relevant. Allotropes of elemental carbon graphene a single layer of graphite 1. Tunable graphene dc superconducting quantum interference device. Zettl,1,2, and irfan siddiqi,1,4 1department of physics, university of california, berkeley, california 94720, usa 2materials sciences division, lawrence berkeley national laboratory, berkeley. Current saturation in zerobandgap, topgated graphene fieldeffect transistors i meric, my han, af young, b ozyilmaz, p kim, kl shepard nature nanotechnology 3 11, 654659, 2008. Dec, 2010 as a result, quantum mechanical effects when the system is confined or subjected to potentials at the nanoscale may be quite different from what happens in conventional electronic systems. All our devices are made with more than 60 metal lines to ensure good periodicity. Quantum interference and klein tunnelling in graphene. Nanoribbons closed into short nanotubes have spectra that are sensitive to the precise boundary termination of the ring, and may behave in a complicated way as the width is varied nakamura et al. Kt can be simply observed as the opening of a transmission window inside the grating stop band, provided that the impressed chirp is. Quantum interference and klein tunneling in graphene heterojunctions andrea f. Scattering of a ballistic electron by the quantum dot spin qubits fixed in a graphene nanoribbon is investigated theoretically.

Kimquantum interference and klein tunnelling in graphene heterojunctions. We study the spectrum of particleinabox states for single and bilayer graphene, corresponding to massless and massive twodimensional 2d fermions. Tuning the valley and chiral quantum state of dirac. Graphene transistor based on tunable dirac fermion optics pnas. Request pdf quantum interference and klein tunneling in graphene heterojunctions the observation of quantum conductance oscillations in mesoscopic systems has traditionally required the. Young af, kim p 2009 quantum interference and klein tunnelling in graphene heterojunctions. Consider motion of massless dirac fermions in an external potential, as described by the hamiltonian.

Blg was chosen because the presence of klein tunneling in monolayer graphene results in the absence of local gap openings. Shot noise measurements can provide insight into the modemixing mechanism supplementary figs 1 and 4. Graphene is a 2d material with a honeycomb lattice structure made of sp2 bonded carbon atoms. Researchers used scotch tape to peel off layers from graphite, transferred them onto a silicon surface, and used an optical technique to find individual graphene sheets. Superklein tunneling refers to the omnidirectional total transmission of quantum. Imaging electrostatically confined dirac fermions in graphene. Graphene rings have been studied by several groups. Distinguishing lead and molecule states in graphenebased. Quantum interference effects in chemical vapor deposited graphene. Quantum simulation of the klein paradox quantum optics.

Graphene transistor based on tunable dirac fermion optics. Berry phases typically have been accessed through interference experiments. Pdf quantum interference and klein tunnelling in graphene. Insights about relativistic qm from graphene quantum hall effect in graphene.

Electronhole hybridization in bilayer graphene national. Quantum interference within the graphene leads gives rise to an energydependent transmission and fluctuations in the sequential tunnelrates. Graphene, a monolayer honeycomb lattice of carbon atoms, provides a unique platform for studying twodimensional relativistic quantum physics and for developing novel quantuminformation devices. Today the availability of high mobility graphene up to room temperature makes. Efficient quantum transport simulation for bulk graphene. Interference and tunneling are two signature quantum effects that are often perceived as the yin and yang of quantum mechanics. We study the spectrum of particle in abox states for single and bilayer graphene, corresponding to massless and massive twodimensional 2d fermions. Quantum tunnelling or tunneling us is the quantum mechanical phenomenon where a subatomic particles probability disappears from one side of a potential barrier and appears on the other side without any probability current flow appearing inside the well. We present transport measurements on a strongly coupled graphene quantum dot in a perpendicular magnetic field.

The ones marked may be different from the article in the profile. Graphene is a onelayer honeycomb lattice of carbon atoms. Investigations of charge carrier transport across such a pn junction pnj have revealed unique phenomena reflecting the dirac fermion character in graphene, such as klein tunneling 1,2,3, veselago lensing 4 and snake state 5,6. Quantum interference effects in chemical vapor deposited. Dirac equation and quantum relativistic effects in a single trapped ion, l.

Atomistic quantum transport modeling of metalgraphene. The klein paradox role of chirality klein tunneling in singlelayer graphene klein tunneling and conductivity. This results in a destructive interference between the time. Graphene, a twodimensional carbon c atomic layer with a hexagonal network, exhibits various unique and excellent properties. While electron optics such as lensing and focusing. Quantum interference and klein tunnelling in graphene heterojunctions, nature physics, band 5, 2009, s. Aug 23, 2011 interference and tunneling are two signature quantum effects that are often perceived as the yin and yang of quantum mechanics. The effective incorporation of the gqds extends the light absorption of the tio2 nanoparticles from uv to a wide visible region.

Graphene heterojunctions offer the opportunity to study an old problem in relativistic quantum mechanics. Here we report singleelectron tunneling through a molecule that has been anchored to two graphene leads. Intravalley scattering by topological defects breaking chirality. Quantum interference and klein tunnelling in graphene heterojunctions article in nature physics 53. Tunnelinginjection in vertical quasi2d heterojunctions. Commonpath interference and oscillatory zener tunneling in. Atomistic quantum transport modeling of metalgraphene nanoribbon heterojunctions i. Angledependent transmission in graphene heterojunctions. Aharonovbohm effect in an electronhole graphene ring system. Currentphase relation in graphene and application to a. We report here the fabrication and operation of a two junction dc superconducting quantum interference device squid formed by a single graphene sheet contacted with aluminumpalladium electrodes in the geometry of a loop. Here we demonstrate that the dirac quasiparticles in graphene provide a dramatic. Quantum interference and klein tunneling in graphene heterojunctions authors.

For the first case, it is shown that the klein tunneling in a graphene sheet leads to a final. Diraclike quasiparticles ingraphene graphene is a single layer of carbon atoms densely packed in a. One notable example is klein tunneling, a phenomena in which electrons convert to holes. The structural and electronic properties of graphenegraphenelike aluminum nitrides monolayer grgaln heterojunction with and without vacancies are systematically investigated by firstprinciples calculation. Stacked layers of graphene make graphite, or pencil lead. We report several quantum interference effects in graphene grown by chemical vapor deposition. Efficient separation of electronhole pairs in graphene. Chiral tunnelling and the klein paradox in graphene, published online.

Quantum interference and klein tunnelling in graphene heterojunctions, nature. Jun 27, 2016 electrostatic confinement of charge carriers in graphene is governed by klein tunnelling, a relativistic quantum process in which particlehole transmutation leads to unusual anisotropic. An onoff berry phase switch in circular graphene resonators. When an electron completes a cycle around the dirac point a particular location in graphenes electronic structure, the phase of its wave function changes by this socalled berry phase is tricky to observe directly in solidstate measurements. Dec 19, 2019 blg was chosen because the presence of klein tunneling in monolayer graphene results in the absence of local gap openings. Quantum simulation of the klein paradox quantum optics and.

Kim p 2009 quantum interference and klein tunnelling in graphene heterojunctions. The device consists of an etched singlelayer graphene flake with two narrow constrictions separating a 140 nm diameter island from source and drain graphene contacts. Chiral dynamics and klein tunneling of lowenergy quasiparticles in graphene. Monodispersed graphene quantum dots were sparsely deposited onto tio2 nanoparticles to form visiblelightresponse heterojunctions for effective separation of electron. The featureless back gate homogeneously doped the channel, whereas the periodic top gate independently induced density modulation in the blg. Watersoluble, singlecrystalline, and aminefunctionalized graphene quantum dots gqds with absorption edge at. We present a theory of quantumcoherent transport through a lateral pnp structure in graphene, which fully accounts for the interference of forward and backward scattering on the pn interfaces. Firstprinciples theoretical investigation of graphene layers. In an experiment carried out in 2009, our group has performed a quantum simulation of the dirac equation using a single trapped ion and observed so called zitterbewegung, a peculiar quivering motion of free relativistic quantum particles predicted by the dirac equation. Only internal quantum interference between different raman scattering processes explains the narrow line widths of the 2d band or the absence of phonons with q k in the raman spectrum of graphene 4.

Mechanically controlled quantum interference in graphene. Young a f and kim p 2009 quantum interference and klein tunnelling in graphene heterojunctions nat. Quantum hall effect in gapped graphene heterojunctions j. Towards graphene based quantum interference devices 2 1. We present a beam splitter in a suspended, ballistic, multiterminal, bilayer graphene device.

Quantum hall effect in gapped graphene heterojunctions. Graphene provides a twodimensional platform for contacting individual molecules, which enables transport spectroscopy of molecular orbital, spin, and vibrational states. Tunable symmetry breaking and helical edge transport in a graphene quantum spin hall state. Scattering of a ballistic electron by the quantumdot spin qubits fixed in a graphene nanoribbon is investigated theoretically. December 1, 2008 the observation of quantum conductance oscillations in mesoscopic systems has traditionally. Some studies adopt simplified boundary conditions allowing for studies using the. In graphene, owing to the linear and gapless band structure, ntype electronlike and ptype holelike regions can adjoin without a gap in between.

Graphene is known as the worlds thinnest material due to its 2d structure, in which each sheet is only one carbon atom thick, allowing each atom to engage in a chemical reaction from two sides. Introduction graphene is a promising candidate for replacing semiconductors as the basic material for the design of new nanodevices due to its truly twodimensional geometry as well as large carrier mobility 1. Transport through a strongly coupled graphene quantum dot. We study the total transmission of quantum particles satisfying the kleingordon equation through a potential barrier. Tuning the valley and chiral quantum state of dirac electrons. A photonic analogue of klein tunneling kt, that is, of the exotic property of relativistic electrons to pass a large repulsive and sharp potential step, is proposed for pulse propagation in a nonuniform fiber bragg grating with an embedded chirped region. We report on the observation of quantum transport and interference in a graphene device that is attached with a pair of split gates to form an electrostaticallydefined quantum point contact qpc. Quantum interference and klein tunnelling in graphene heterojunctions.

The quantum transport formalism based on tightbinding models is known to be powerful in dealing with a wide range of open physical systems subject to external driving forces but is, at the same. Quantum interference within the graphene leads gives rise to an energydependent transmission and fluctuations in the. Commonpath interference and oscillatory zener tunneling. The chiral properties of dirac electrons in monolayer graphene and the berry phase. Superklein tunneling of kleingordon particles sciencedirect. Their combined citations are counted only for the first article. Electrostatic confinement of charge carriers in graphene is governed by klein tunnelling, a relativistic quantum process in which particlehole transmutation leads to unusual anisotropic. While electron optics such as lensing and focusing have been demonstrated experimentally, building a collimated electron interferometer in two unconfined. Neutrons reveal quantum tunnelling on graphene enables.

We observe a splitting of the zerodensity lines of the two layers with. We also stress that klein tunneling is not a genuine quantum tunneling effect as it does not necessarily involve. Firstprinciples theoretical investigation of graphene. Imaging electrostatically confined dirac fermions in. Nori, science 326, 108 2009 pdf 5 quantum interference and klein tunnelling in graphene heterojunctions, a. Tunable quantum interference in bilayer graphene in double. A quantum critical point emergent relativistic quantum mechanics. Chiral tunnelling and the klein paradox in graphene. Fieldeffect tunneling transistor based on vertical graphene heterostructures. By using local bottomgates, a pn interface tilted with respect to the current direction can be formed.

Using local gates, one can create tunable heterojunctions in graphene, isolating the. The electronic thickness of graphene science advances. Mechanically controlled quantum interference in graphene break. A kleintunneling transistor with ballistic graphene.

Quantum interference in graphene sensitivity to elastic scattering. Tunable symmetry breaking and helical edge transport in a. Shot noise generated by graphene pn junctions in the. Tunable fewelectron double quantum dots and klein tunnelling in ultraclean carbon nanotubes g. Friday, 11 february 2011 quantum simulation of the klein paradox. Tunable graphene dc superconducting quantum interference. Klein gordon equation 2 2 2224 2 22224 2 ecp mc c mc t. Lateral graphene gates are used to electrostatically tune the device. A new type of quantum interference device based on a graphene nanoring in which. Graphene is essentially the mother of all graphitic materials it can be formed into buckyballs and nanotubes, etched into nanoribbons, or stacked into bulk graphite. The device design allows a previously unreported quantitative characterization of the net dfo contribution and leads to improved device performance resilient to abrupt change in temperature. We also stress that klein tunneling is not a genuine quantum tunneling effect as it. Using transport measurements, we investigate the electrostatics of two graphene layers, twisted by. Electron transport through short, phasecoherent metalgraphenemetal devices occurs via resonant transmission through particleinaboxlike states defined by the atomicallysharp metal leads.