1,723,608 research outputs found
Conduction properties of extended defect states in Dirac materials
No full textWe demonstrate the existence of localized states in close vicinity of a linear defect in graphene. These states have insulating or conducting character. Insulating states form a flat band, while conducting states present a slowdown of the group velocity which is not originated by many-body interactions and it is controlled by the interface properties. For appropriate boundary conditions, the conducting states exhibit momentum-valley locking and protection from backscattering effects. These findings provide a contribution to the recent discussion on the origin of correlated phases in graphene
Topological current divider
No full textWe study the transport properties of a hybrid junction made of a ferromagnetic lead in electrical connection with the helical edge modes of a two-dimensional topological insulator. In this system, the time-reversal symmetry, which characterizes the ballistic edge modes of the topological insulator, is explicitly broken inside the ferromagnetic region. This conflict situation generates unusual transport phenomena at the interface which are the manifestation of the interplay between the spin polarization of the injected current and the spin-momentum locking mechanism operating inside the topological insulator. We show that the spin-polarized current originated in the ferromagnetic region is asymmetrically divided in spatially separated branch currents sustained by edge channels with different helicity inside the topological insulator. The above findings provide the working principle of a topological current divider in which the relative intensity of the branch currents is determined by the polarization of the incoming current. We discuss the relevance of this effect in spintronics where, for instance, it offers an alternative way to measure the current polarization generated by a ferromagnetic electrode
Valley to charge current conversion in graphene linear defects
No full textThe conduction properties of a graphene-graphene junction originated by a linear defect are analyzed. We provide a generalization of the Dirac Hamiltonian model taking into account the Fermi velocity gradient at the interface. General boundary conditions for the scattering problem are derived within the framework of the matching matrix method. We show that the scattering properties of the interface, as predicted by the theory, strongly depend on the boundary conditions used. We demonstrate that a charge current is established at the linear defect interface when a valley-polarized current impinges on it. These findings provide the working principle of a valley to charge current converter, which is relevant for the emergent field of valleytronics
Genesis of the Concept of Topological Current Divider: From Valleytronics to Spintronics
No full text
Invariant representation of propagation propekties for bi-coupled periodic structures
No full textGeneral bi-coupled periodic systems are dealt with by means of transfer matrices of single units. The solutions of the associated characteristic equation are discussed in terms of invariant quantities by exploiting the well-known reversibility of its coefficients. An exhaustive description of the free wave propagation patterns is given on the invariant plane where propagation domains with qualitatively different character are identified. The asymptotic behavior of the roots of the characteristic equation when the invariants tend to infinity is analyzed. The contour plot of the real part of the propagation constants, responsible for the amount of attenuation of the characteristic waves, is illustrated on the invariants' plane. Next, several models of bi-coupled periodic structures made up of beams resting on elastic supports are considered. A non-linear mapping from the invariants' plane to the physical parameters plane provides a concise representation of the pattern of the propagation domains. A mechanical interpretation associated with the boundaries of these regions is given. Finally, the proper selection of the physical parameters governing the propagation modes is discussed. (C) 2002 Elsevier Science Ltd. All rights reserved
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