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Pseudospin plays a central role in many novel physical properties of graphene and other artificial systemswhich have pseudospins of 1/2. Here we show that in certain photonic crystals (PCs) exhibiting conical dispersions at k = 0, the eigenmodes near the "Dirac-like point" can be described by an effective spin-orbit Hamiltonian with a higher dimension value S = 1, treating the wave propagation in positive index (upper cone), negative index (lower cone), and zero index (flat band) media within a unified framework. The three-component spinor gives rise to boundary conditions distinct from those of pseudospin 1/2, leading to wave transport behaviors as manifested in super Klein tunneling and supercollimation. For example, collimation can be realized more easily with pseudospin 1 than pseudospin 1/2. The effective medium description of the PCs allows us to further understand the physics of pseudospin-1 electromagnetic (EM) waves from the perspective of complementary materials. The special wave scattering properties of pseudospin-1 EM waves, in conjunction with the discovery that the effective photonic potential can be varied by a simple change of length scale, offer ways to control photon transport. As a useful platform to study pseudospin-1 physics, dielectric PCs are much easier to fabricate and characterize than ultracold atom systems proposed previously. The system also provides a platform to realize the concept of "complementary medium" using dielectric materials and has the unique advantage of low loss. [ABSTRACT FROM AUTHOR]

The light-dressing effect in Xe atoms was identified in laser-assisted elastic electron scattering (LAES) signals. In the angular distribution of LAES signals with energy shifts of ±hw recorded by the scattering of 1 keV electrons by Xe in an intense nonresonant laser field, a peak profile appeared at small scattering angles (<0.5°). This peak was interpreted as evidence of the light dressing of Xe atoms induced by an intense laser field on the basis of a numerical simulation in which the light-dressing effect is included. [ABSTRACT FROM AUTHOR]

The nonequilibrium dynamics beyond the linear response of Weyl semimetals is studied after a sudden switching on of a dc electric field. The resulting current is a nonmonotonic function of time with an initial quick increase in polarization current followed by a power-law decay. Particle-hole creation à la Schwinger dominates for long times when the conduction current takes over the leading role with the total current increasing again. The conductivity estimated from a dynamical calculation within a generalized Drude picture agrees with the one obtained from Kubo's formula. The full distribution function of electron-hole pairs changes from Poissonian for short perturbations to a Gaussian in the long perturbation (Landau-Zener) regime. The vacuum persistence probability of high-energy physics manifests itself in a finite probability of no pair creation and no induced current at all times. [ABSTRACT FROM AUTHOR]

We employ the tight-binding propagation method to study Klein tunneling and quantum interference in large graphene systems. With this efficient numerical scheme, we model the propagation of a wave packet through a potential barrier and determine the tunneling probability for different incidence angles. We consider both sharp and smooth potential barriers in n-p-n and n-n' junctions and find good agreement with analytical and semiclassical predictions. When we go outside the Dirac regime, we observe that sharp n-p junctions no longer show Klein tunneling because of intervalley scattering. However, this effect can be suppressed by considering a smooth potential. Klein tunneling holds for potentials changing on the scale much larger than the interatomic distance. When the energies of both the electrons and holes are above the Van Hove singularity, we observe total reflection for both sharp and smooth potential barriers. Furthermore, we consider caustic formation by a two-dimensional Gaussian potential. For sufficiently broad potentials we find a good agreement between the simulated wave density and the classical electron trajectories. [ABSTRACT FROM AUTHOR]

We report the experimental observation of Fabry-Pérot interference in the conductance of a gate-defined cavity in a dual-gated bilayer graphene device. The high quality of the bilayer graphene flake, combined with the device's electrical robustness provided by the encapsulation between two hexagonal boron nitride layers, allows us to observe ballistic phase-coherent transport through a 1-μm-long cavity. We confirm the origin of the observed interference pattern by comparing to tight-binding calculations accounting for the gate-tunable band gap. The good agreement between experiment and theory, free of tuning parameters, further verifies that a gap opens in our device. The gap is shown to destroy the perfect reflection for electrons traversing the barrier with normal incidence (anti-Klein tunneling). The broken anti-Klein tunneling implies that the Berry phase, which is found to vary with the gate voltages, is always involved in the Fabry-Perot oscillations regardless of the magnetic field, in sharp contrast with single-layer graphene. [ABSTRACT FROM AUTHOR]

The article discusses the parities and spins of the odd-A phosphorus isotopes within elastic magnetic electron-scattering theory. It mentions that spin and parity are being the fundamental properties of nuclei. It presents the pairing off of nucleon spins and orbital momenta in a nucleus to produce zero contribution to the whole nucleus.

Using the coupled series expansion method developed in this paper, we have investigated the quantum behavior of Coulomb impurity states under external electric and magnetic fields in graphene. Under magnetic field, we have obtained an accurate full spectrum of the attractive and repulsive Coulomb impurities for both massless and massive Dirac electrons and have found that bound states can be tuned between in and out of the gap by Coulomb impurities and a magnetic field. When a linear radial electric field in combination with a magnetic field are applied, the energy levels of Coulomb impurity states experience intercrossing, and they disappear because of Klein tunneling as the electric field exceeds the magnetic field. The results are helpful in controlling Coulomb impurity states by external fields in graphene and the method proves to be an efficient way to obtain accurate solutions of the Dirac equation with various fields. [ABSTRACT FROM AUTHOR]

We consider electrostatically coupled quantum dots in topological insulators, otherwise confined and gapped by a magnetic texture. By numerically solving the (2+1) Dirac equation for the wave packet dynamics, we extract the energy spectrum of the coupled dots as a function of bias-controlled coupling and an external perpendicular magnetic field. We show that the tunneling energy can be controlled to a large extent by the electrostatic barrier potential. Particularly interesting is the coupling via Klein tunneling through a resonant valence state of the barrier. The effective three-level system nicely maps to a model Hamiltonian, from which we extract the Klein coupling between the confined conduction and valence dots levels. For large enough magnetic fields Klein tunneling can be completely blocked due to the enhanced localization of the degenerate Landau levels formed in the quantum dots. [ABSTRACT FROM AUTHOR]

We show that the features of Klein tunneling make graphene a unique interface for implementing low control quantum gates between static and mobile qubits. A ballistic electron spin is considered as the mobile qubit, while the static qubit is the electronic spin of a quantum dot fixed in a graphene nanoribbon. Scattering is the low control mechanism of the gate, which in other systems is very difficult to exploit because of both backscattering and the momentum dependence of transmission. We find that the unique features of Klein tunneling enable quasideterministic quantum gates between the spin of a ballistic electron and a static spin held in a dot, regardless of the momenta or the shape of the incident electron wave function. The Dirac equation is used to describe the system in the one particle approximation, with the interaction between the static and the mobile spins modeled by a Heisenberg Hamiltonian. Furthermore, we discuss an application of this model to generate entanglement between two well-separated static qubits. [ABSTRACT FROM AUTHOR]

We investigate the quantum tunneling of electrons in an AA-stacked bilayer graphene (BLG) n-p junction and n-p-n junction. We show that Klein tunneling of an electron can occur in this system. The quasiparticles are not only chiral but are additionally described by a "cone index." Due to the orthogonality of states with different cone indexes, electron transport across a potential barrier must strictly conserve the cone index, and this leads to the protected cone transport which is unique in AA-stacked BLG. Together with the negative refraction of electrons, electrons residing in different cones can be spatially separated according to their cone index when transmitted across an n-p junction. This suggests the possibility of "cone-tronic" devices based on AA-stacked BLG. Finally, we calculate the junction conductance of the system. [ABSTRACT FROM AUTHOR]

The next-nearest-neighbor hopping term t′ determines a magnitude, and, hence, the importance of several phenomena in graphene that include self-doping due to broken bonds and the Klein tunneling, which in the presence of t′, is no longer perfect. Theoretical estimates for t′ vary widely, whereas a few existing measurements by using polarization-resolved magnetospectroscopy have found surprisingly large t′, close to or even exceeding the highest theoretical values. Here, we report dedicated measurements of the density of states in graphene by using high-quality capacitance devices. The density of states exhibits a pronounced electron-hole asymmetry that increases linearly with energy. This behavior yields t′ ≈ - 0.3 eV ± 15%, in agreement with the high end of theory estimates. We discuss the role of electron-electron interactions m determining t′ and overview phenomena, which can be influenced by such a large value of t′. [ABSTRACT FROM AUTHOR]

Currently, much effort is being put into detecting unconventional p-wave superconductivity in Josephson junctions based on topological insulators (TIs). For that purpose we propose to use superconducting Klein tunneling, i.e., the reflectionless passage of Cooper pairs through a potential barrier in a gated ballistic junction. This phenomenon occurs due to the fact that the supercurrent is carried by helical Andreev bound states (ABSs) characterized by spin-momentum locking similar to the normal-state carriers. We derive the spectrum of the helical ABSs and the corresponding Josephson current for a junction made on the surface of a three-dimensional TI. The superconducting Klein tunneling is predicted to yield a nonsinusoidal current-phase relation and an anomalous critical current Ic that does not vanish with increasing barrier strength. We also analyze the dependence of the IcRn product (where Rn is the normal-state junction resistance) on the microscopic parameters of the superconductor/TI interface, which leads to lower IcRn values than expected from previous models of the proximity-effect Josephson junctions. [ABSTRACT FROM AUTHOR]

The perfect transmission in a graphene monolayer and the perfect reflection in a Bernal graphene bilayer for electrons incident in the normal direction of a potential barrier are viewed as two incarnations of the Klein paradox. Here we show a new and unique incarnation of the Klein paradox. Owing to the different chiralities of the quasiparticles involved, the chiral fermions in a twisted graphene bilayer show an adjustable probability of chiral tunneling for normal incidence: they can be changed from perfect tunneling to partial or perfect reflection, or vice versa, by controlling either the height of the barrier or the incident energy. As well as addressing basic physics about how the chiral fermions with different chiralities tunnel through a barrier, our results provide a facile route to tune the electronic properties of the twisted graphene bilayer. [ABSTRACT FROM AUTHOR]

The electronic tunneling properties of the two stable forms of trilayer graphene (TLG), rhombohedral ABC and Bernal ABA, are examined for p-n and p-n-p junctions as realized by using a single gate (SG) or a double gate (DG). For the rhombohedral form, due to the chirality of the electrons, the Klein paradox is found at normal incidence for SG devices, while at high-energy interband scattering between additional propagation modes can occur. The electrons in Bernal ABA TLG can have a monolayer- or bilayer-like character when incident on a SG device. Using a DO, however, both propagation modes will couple by breaking the mirror symmetry of the system, which induces intermode scattering and resonances that depend on the width of the DG p-n-p junction. For ABC TLG the DG opens up a band gap which suppresses Klein tunneling. The DG induces also an unexpected asymmetry in the tunneling angle for single-valley electrons. [ABSTRACT FROM AUTHOR]

The role of defect-induced zero-energy modes on charge transport in graphene is investigated using Kubo and Landauer transport calculations. By tuning the density of random distributions of monovacancies either equally populating the two sublattices or exclusively located on a single sublattice, all conduction regimes are covered from direct tunneling through evanescent modes to mesoscopic transport in bulk disordered graphene. Depending on the transport measurement geometry, defect density, and broken sublattice symmetry, the Dirac-point conductivity is either exceptionally robust against disorder (supermetallic state) or suppressed through a gap opening or by algebraic localization of zero-energy modes, whereas weak localization and the Anderson insulating regime are obtained for higher energies. These findings clarify the contribution of zero-energy modes to transport at the Dirac point, hitherto controversial. [ABSTRACT FROM AUTHOR]

Guided by the analogy to Mie scattering of light on small particles, we show that the propagation of a Dirac-electron wave in graphene can be manipulated by a circular gated region acting as a quantum dot. Large dots enable electron lensing, while for smaller dots resonant scattering entails electron confinement in quasibound states. Forward scattering and Klein tunneling can be almost switched off for small dots by a Fano resonance arising from the interference between resonant scattering and the background partition. [ABSTRACT FROM AUTHOR]

The quantum capacitance model is applied to obtain an exact solution for the space-resolved carrier density in a multigated doped graphene sheet at zero temperature, with quantum correction arising from the finite electron capacity of the graphene itself taken into account. The exact solution is demonstrated to be equivalent to the self-consistent Poisson-Dirac iteration method by showing an illustrative example, where multiple gates with irregular shapes and a nonuniform dopant concentration are considered. The solution therefore provides a fast and accurate way to compute spatially varying carrier density, on-site electric potential energy, as well as quantum capacitance for bulk graphene, allowing for any kind of gating geometry with any number of gates and any types of intrinsic doping. [ABSTRACT FROM AUTHOR]

We investigate theoretically spin injection efficiency from the ferromagnetic graphene to normal graphene (FG/NG) based on electron optics, where the magnetization in the FG is assumed from the magnetic proximity effect. Based on a graphene lattice model, we demonstrated that one spin-species electron flow from a point source could be nearly suppressed through the FG-NG interface, when the total internal reflection effect occurs with the help of an additional barrier masking the Klein tunneling, while the opposite spin-species electron flow could even be collimated due to the negative refraction under suitable parameters. Not only at the focusing point is the efficient spin injection achieved, but in the whole NG region the spin injection efficiency can also be maintained at a high level. It is also shown that the nonideal FG-NG interface could reduce the spin injection efficiency since the electron optics phenomena are weakened owing to the interfacial backscattering. Our findings may shed light on making graphene-based spin devices in the spintronics field. [ABSTRACT FROM AUTHOR]

In the present work, we investigate how stmcmral defects in graphene can change its transport properties. In particular, we show that breaking of the sublattice symmetry in a graphene monolayer overcomes the Klein effect, leading to confined states of massless Dirac fermions. Experimentally, this corresponds to chemical bonding of foreign atoms to carbon atoms, which attach themselves to preferential positions on one of the two sublattices. In addition, we consider the scattering off a tensor barrier, which describes the rotation of the honeycomb cells of a given region around an axis perpendicular to the graphene layer. We demonstrate that in this case the intervalley mixing between the Dirac points emerges, and that Klein tunneling occurs. [ABSTRACT FROM AUTHOR]

Within an effective Dirac theory the low-energy dispersions of monolayer graphene in the presence of Rashba spin-orbit coupling and spin-degenerate bilayer graphene are described by formally identical expressions. We explore implications of this correspondence for transport by choosing chiral tunneling through pn and pnp junctions as a concrete example. A real-space Green's function formalism based on a tight-binding model is adopted to perform the ballistic transport calculations, which cover and confirm previous theoretical results based on the Dirac theory. Chiral tunneling in monolayer graphene in the presence of Rashba coupling is shown to indeed behave like in bilayer graphene. Combined effects of a forbidden normal transmission and spin separation are observed within the single-band n ↔ p transmission regime. The former comes from real-spin conservation, in analogy with pseudospin conservation in bilayer graphene, while the latter arises from the intrinsic spin-Hall mechanism of the Rashba coupling. [ABSTRACT FROM AUTHOR]

We show that in gapped bilayer graphene, quasiparticle tunneling and the corresponding Berry phase can be controlled such that they exhibit features of single-layer graphene such as Klein tunneling. The Berry phase is detected by a high-quality Fabry-Pérot interferometer based on bilayer graphene. By raising the Fermi energy of the charge carriers, we find that the Berry phase can be continuously tuned from 2π down to 0.68π in gapped bilayer graphene, in contrast to the constant Berry phase of 2π in pristine bilayer graphene. Particularly, we observe a Berry phase of π, the standard value for single-layer graphene. As the Berry phase decreases, the corresponding transmission probability of charge carriers at normal incidence clearly demonstrates a transition from anti-Klein tunneling to nearly perfect Klein tunneling. [ABSTRACT FROM AUTHOR]

We study the Landau levels (LLs) of a Weyl semimetal with two adjacent Weyl nodes. We consider different orientations η = &# 8736; (B, k0) of magnetic field B with respect to k0, the vector of Weyl node splitting. A magnetic field facilitates the tunneling between the nodes, giving rise to a gap in the transverse energy of the zeroth LL. We show how the spectrum is rearranged at different η and how this manifests itself in the change of behavior of the differential magnetoconductance d G (B) / d B of a ballistic p - n junction. Unlike the single-cone model where Klein tunneling reveals itself in positive d G (B) / d B, in the two-cone case, G (B) is nonmonotonic with a maximum at Bc ∝ Φ0 k²0 / ln (k0 lE) for large k0 lE, where lE = √ ħ v / | e | E, with E for the built-in electric field and Φ 0 for the magnetic flux quantum. [ABSTRACT FROM AUTHOR]

We develop an analytical mode-matching technique for the tight-binding model to describe electron transport across graphene P-N junctions. This method shares the simplicity of the conventional modematching technique for the low-energy continuum model and the accuracy of the tight-binding model over a wide range of energies. It further reveals an interesting phenomenon on a sharp P-N junction: the disappearance of the well-known Klein tunneling (i.e., perfect transmission) at normal incidence and the appearance of perfect transmission at oblique incidence due to trigonal warping at energies beyond the linear Dirac regime. We show that this phenomenon arises from the conservation of a generalized pseudospin in the tight-binding model. We expect this effect to be experimentally observable in graphene and other Dirac fermions systems, such as the surface of three-dimensional topological insulators. [ABSTRACT FROM AUTHOR]

Klein tunneling, the perfect transmission of normally incident Dirac electrons across a potential barrier, has been widely studied in graphene and explored to design switches, albeit indirectly. We show an alternative way to directly measure Klein tunneling for spin-momentum locked electrons crossing a PN junction along a three-dimensional topological insulator surface. In these topological insulator PN junctions (TIPNJs), the spin texture and momentum distribution of transmitted electrons can be measured electrically using a ferromagnetic probe for varying gate voltages and angles of current injection. Based on transport models across a TIPNJ, we show that the asymmetry in the potentiometric signal between PP and PN junctions and its overall angular dependence serve as a direct signature of Klein tunneling. [ABSTRACT FROM AUTHOR]

In graphene and other massless two-dimensional Dirac materials, Klein tunneling compromises electron confinement, and momentum-space contours can be assigned a Berry phase which is either zero or π. Consequently, in such systems the energy spectrum of circular potential wells exhibits an interesting discontinuity as a function of magnetic field B: for a given angular momentum the ladder of eigenresonances is split at an energy-dependent critical field Bc. Here we show that introducing a mass term Δ in the Hamiltonian bridges this discontinuity in such a way that states below Bc are adiabatically connected to states above Bc whose principal quantum number differs by unity depending on the sign of Δ. In the B-Δ plane, the spectrum of these circular resonators resembles a spiral staircase, in which a particle prepared in the |n,m⟩ resonance state can be promoted to the |n±1,m> state by an adiabatic circuit of the Hamiltonian about Bc, the sign depending on the direction of the circuit. We explain the phenomenon in terms of the evolving Berry phase of the orbit, which in such a circuit changes adiabatically by 2π. [ABSTRACT FROM AUTHOR]

We investigate the interplay between confinement and the fermion doubling problem in Dirac-like Hamiltonians. Individually, both features are well known. First, simple electrostatic gates do not confine electrons due to the Klein tunneling. Second, a typical lattice discretization of the first-order derivative k → - i∂x skips the central point and allow spurious low-energy, highly oscillating solutions known as fermion doublers. While a no-go theorem states that the doublers cannot be eliminated without artificially breaking a symmetry, here we show that the symmetry broken by the Wilson's mass approach is equivalent to the enforcement of hard-wall boundary conditions, thus making the no-go theorem irrelevant when confinement is foreseen. We illustrate our arguments by calculating the following: (i) the band structure and transport properties across thin films of the topological insulator Bi2 Se3, for which we use ab initio density functional theory calculations to justify the model; and (ii) the band structure of zigzag graphene nanoribbons. [ABSTRACT FROM AUTHOR]

We study time-dependent electron transport and quantum noise in a ballistic graphene field effect transistor driven by an ac gate potential. The nonlinear response to the ac signal is computed through Floquet theory for scattering states and Landauer-Büttiker theory for charge current and its fluctuations. Photon-assisted excitation of a quasibound state in the top-gate barrier leads to resonances in transmission that strongly influence the noise properties. For strong doping of graphene under source and drain contacts, when electrons are transmitted through the channel via evanescent waves, the resonance leads to a substantial suppression of noise. The Fano factor is then reduced well below the pseudodiffusive value, F < 1/3, also for strong ac drive. The good signal-to-noise ratio (small Fano factor) on resonance suggests that the device is a good candidate for high-frequency (THz) radiation detection. We show analytically that Klein tunneling (total suppression of back-reflection) persists for perpendicular incidence also when the barrier is driven harmonically. Although the transmission is inelastic and distributed among sideband energies, a sum rule leads to total suppression of shot noise. [ABSTRACT FROM AUTHOR]

We study the spin current injected by spin pumping into single layer graphene and the two-dimensional electron gas (2DEG) with ferromagnetic contacts using scattering theory. The spin currents pumped into graphene are very distinct from that into the 2DEG since they are affected by Klein tunneling. [ABSTRACT FROM AUTHOR]

We report unusual physics associated with wave scattering in pseudospin-1 systems whose band structure consists of a conventional Dirac cone and a topologically flat band. First, for small scatterer size, we find a surprising revival resonant scattering phenomenon and identify a peculiar type of boundary trapping profile through the formation of unusual vortices as the physical mechanism. Second, for larger scatterer size, a perfect caustic phenomenon arises as a manifestation of the super-Klein tunneling effect, leading to the scatterer's being effectively as a Veselago lens. Third, in the far scattering field, an unexpected isotropic behavior emerges at low energies, which can be attributed to the vanishing Berry phase for massless pseudospin-1 particles and, consequently, to constructive interference between the time-reversed backscattering paths. We develop an analytic theory based on the generalized Dirac-Weyl equation to fully explain these phenomena and articulate experimental schemes with photonic or electronic systems. [ABSTRACT FROM AUTHOR]

We study the zero temperature conductance and magnetoconductance of ballistic p-n junctions in Weyl semimetals. Electron transport is mediated by Klein tunneling between the n and p regions. The chiral anomaly that is realized in Weyl semimetals plays a crucial role in the magnetoconductance of the junction. With the exception of field orientations where the angle between B and the junction plane is small, magnetoconductance is positive and linear in B at both weak and strong magnetic fields. In contrast, magnetoconductance in conventional p-n junctions is always negative. [ABSTRACT FROM AUTHOR]

We study by first-principles calculations a densely packed island of organic molecules (F4TCNQ) adsorbed on graphene. We find that with electron doping the island naturally forms a p-n junction in the graphene sheet. For example, a doping level of ~3×1013 electrons per cm² results in a p-n junction with an 800 meV electrostatic potential barrier. Unlike in a conventional p-n junction in graphene, in the case of the junction formed by an adsorbed organic molecular island we expect that the Klein tunneling is inhibited, even without an applied external magnetic field. Here Klein tunneling is inhibited by the ferromagnetic order that spontaneously occurs in the molecular island upon doping. We estimate that the magnetic barrier in the graphene sheet is around 10 mT. [ABSTRACT FROM AUTHOR]

The band structure of a type-II Weyl semimetal has pairs of electron and hole pockets that coexist over a range of energies and touch at a topologically protected conical point. We identify signatures of this Weyl point in the magnetic quantum oscillations of the density of states, observable in thermodynamic properties. Tunneling between the electron and hole pockets in a magnetic field is the momentum space counterpart of Klein tunneling at a p-n junction in real space. This magnetic breakdown happens at a characteristic field strength that vanishes when the Fermi level approaches the Weyl point. The topological distinction between connected and disconnected pairs of type-II Weyl cones can be distinguished by the qualitatively different dependence of the quantum oscillations on the direction of the magnetic field. [ABSTRACT FROM AUTHOR]

The inherent asymmetry of the electric transport in graphene is attributed to Klein tunneling across barriers defined by pn interfaces between positively and negatively charged regions. By combining conductance and shot noise experiments, we determine the main characteristics of the tunneling barrier (height and slope) in a high-quality suspended sample with Au/Cr/Au contacts. We observe an asymmetric resistance Rodd=100-70Ω across the Dirac point of the suspended graphene at carrier density ||nG|=(0.3-4)?1011cm-2, while the Fano factor displays a nonmonotonic asymmetry in the range Fodd~0.03-0.1. Our findings agree with analytical calculations based on the Dirac equation with a trapezoidal barrier. Comparison between the model and the data yields the barrier height for tunneling, an estimate of the thickness of the pn interface d<20 nm, and the contact region doping corresponding to a Fermi level offset of ~-18 meV. The strength of pinning of the Fermi level under the metallic contact is characterized in terms of the contact capacitance Cc=19?10-6 F/cm². Additionally, we show that the gate voltage corresponding to the Dirac point is given by the difference in work functions between the backgate material and graphene. [ABSTRACT FROM AUTHOR]

A strong in-plane magnetic field drastically alters the low-energy spectrum of bilayer graphene by separating the parabolic energy dispersion into two linear Dirac cones. The effect of this dramatic change on the transport properties strongly depends on the orientation of the in-plane magnetic field with respect to the propagation direction of the charge carriers and the angle at which they impinge on the electrostatic potentials. For magnetic fields oriented parallel to the potential boundaries an additional propagating mode that results from the splitting into Dirac cones enhances the transmission probability for charge carriers tunneling through the potentials and increases the corresponding conductance. Our results show that the chiral suppression of transmission at normal incidence, reminiscent of bilayer graphene's 2π Berry phase, is turned into a chiral enhancement when the magnetic field increases, thus indicating a transition from a bilayer to a monolayer-like system at normal incidence. Further, we find that the typical transmission resonances stemming from confinement in a potential barrier are shifted to higher energy and are eventually transformed into antiresonances with increasing magnetic field. For magnetic fields oriented perpendicular to the potential boundaries we find a very pronounced transition from a bilayer system to two separated monolayer-like systems with Klein tunneling emerging at certain incident angles symmetric around 0, which also leaves a signature in the conductance. For both orientations of the magnetic field, the transmission probability is still correctly described by pseudospin conservation. Finally, to motivate the large in-plane magnetic field, we show that its energy spectrum can be mimicked by specific lattice deformations such as a relative shift of one of the layers. With this equivalence we introduce the notion of an in-plane pseudomagnetic field. [ABSTRACT FROM AUTHOR]

We study Klein tunneling in polariton graphene. We show that the photonic spin-orbit coupling associated with the energy splitting between TE and TM photonic modes can be described as an emergent gauge field. It suppresses the Klein tunneling in a small energy range close to the Dirac points. Thanks to polariton spin-anisotropic interactions, polarized optical pumping allows one to create potential barriers acting on a single polariton spin. We show that the resulting spin-dependent Klein tunneling can be used to create a perfectly transmitting polarization rotator operating at microscopic scale. [ABSTRACT FROM AUTHOR]

A correction to the article "Method for Retrieval of the Three-Dimensional Object Potential by Inversion of Dynamical Electron Scattering" that was published in the 2012 issue is presented.