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Because the valleys in the band structure of graphene are related by time-reversal symmetry, electrons from one valley are reflected as holes from the other valley at the junction with a superconductor. We show how this Andreev reflection…

Mesoscale and Nanoscale Physics · Physics 2013-07-09 A. R. Akhmerov , C. W. J. Beenakker

Minimally twisted bilayer graphene in the presence of an interlayer bias develops a triangular network of valley chiral modes that propagate along the $AB/BA$ interfaces and scatter at the $AA$ regions. The low energy physics of the…

Mesoscale and Nanoscale Physics · Physics 2023-12-07 P. Wittig , F. Dominguez , C. De Beule , P. Recher

Band gap engineering in graphene may open the routes towards transistor devices in which electric current can be switched off and on at will. One may, however, ask if a semiconducting band gap alone is sufficient to quench the current in…

Mesoscale and Nanoscale Physics · Physics 2012-11-12 G. Tkachov , Martina Hentschel

The observation of micron size spin relaxation makes graphene a promising material for applications in spintronics requiring long distance spin communication. However, spin dependent scatterings at the contact/graphene interfaces affect the…

Mesoscale and Nanoscale Physics · Physics 2017-11-02 Ahmet Avsar , Dmitrii Unuchek , Jiawei Liu , Oriol Lopez Sanchez , Kenji Watanabe , Takashi Taniguchi , Barbaros Ozyilmaz , Andras Kis

We have surveyed the in-plane transport properties of the graphene twist bilayer using (i) a low-energy effective Hamiltonian for the underlying electronic structure, (ii) an isotropic elastic phonon model, and (iii) the linear Boltzmann…

Mesoscale and Nanoscale Physics · Physics 2016-12-21 N. Ray , M. Fleischmann , D. Weckbecker , S. Sharma , O. Pankratov , S. Shallcross

Magnetic fields force ballistic electrons injected from a narrow contact to move along skipping orbits and form caustics. This leads to pronounced resistance peaks at nearby voltage probes as electrons are effectively focused inside them, a…

We demonstrate theoretically how local strains in graphene can be tailored to generate a valley polarized current. By suitable engineering of local strain profiles, we find that electrons in opposite valleys (K or K') show different…

Mesoscale and Nanoscale Physics · Physics 2013-05-29 Zhenhua Wu , F. Zhai , F. M. Peeters , H. Q. Xu , Kai Chang

Here we study the evolution of local electronic properties of a twisted graphene bilayer induced by a strain and a high curvature. The strain and curvature strongly affect the local band structures of the twisted graphene bilayer; the…

Mesoscale and Nanoscale Physics · Physics 2015-06-05 Wei Yan , Wen-Yu He , Zhao-Dong Chu , Mengxi Liu , Lan Meng , Rui-Fen Dou , Yanfeng Zhang , Zhongfan Liu , Jia-Cai Nie , Lin He

Valley-polarized currents can be generated by local straining of multi-terminal graphene devices. The pseudo-magnetic field created by the deformation allows electrons from only one valley to transmit and a current of electrons from a…

Mesoscale and Nanoscale Physics · Physics 2016-11-18 S. P. Milovanovic , F. M. Peeters

Strong interaction between electrons in two-dimensional systems in the presence of a high magnetic field gives rise to fractional quantum Hall states that host quasiparticles with fractional charge and fractional exchange statistics. Here,…

We study the quantum valley Hall effect and related domain wall modes in twisted bilayer graphene at a large commensurate angle. Due to the quantum valley and sub-valley Hall effect, a small deviation from the commensurate angle generates…

Mesoscale and Nanoscale Physics · Physics 2023-09-13 Chiranjit Mondal , Rasoul Ghadimi , Bohm-Jung Yang

Strategically combining four structured domains creates the first ever three-way topological energy-splitter; remarkably, this is only possible using a square, or rectangular, lattice, and not the graphene-like structures more commonly used…

Mesoscale and Nanoscale Physics · Physics 2021-06-02 Mehul P. Makwana , Gregory J. Chaplain

Electronic localization is numerically studied in disordered bilayer graphene with an electric-field induced energy gap. Bilayer graphene is a zero-gap semiconductor, in which an energy gap can be opened and controlled by an external…

Mesoscale and Nanoscale Physics · Physics 2009-11-13 Mikito Koshino

Graphene's outstanding mechanical properties lend to strain engineering, allowing for future valleytronics and nanoelectromechanic applications. In this work, we have found that a Gaussian-shaped strain on a graphene p-n junction results in…

Mesoscale and Nanoscale Physics · Physics 2019-07-23 Nojoon Myoung , Hyungkook Choi , Hee Chul Park

In Weyl semimetals the location of linear band crossings, the Weyl cones, is not bound to any high symmetry point of the Brillouin zone, unlike the Dirac nodes in graphene. This flexibility is advantageous for valleytronics, where…

Mesoscale and Nanoscale Physics · Physics 2021-09-29 Serguei Tchoumakov , Bogusz Bujnowski , Jonathan Noky , Johannes Gooth , Adolfo G. Grushin , Jérôme Cayssol

Bilayer graphene has drawn significant attention due to the opening of a band gap in its low energy electronic spectrum, which offers a promising route to electronic applications. The gap can be either tunable through an external electric…

Mesoscale and Nanoscale Physics · Physics 2015-05-27 Gregory M. Rutter , Suyong Jung , Nikolai N. Klimov , David B. Newell , Nikolai B. Zhitenev , Joseph A. Stroscio

A novel spin polarization separation of reflected light is observed, when a linearly polarized Gaussian beam impinges on an air-glass interface at Brewster angle. In the far-field zone, spins of photons are oppositely polarized in two…

Optics · Physics 2015-06-05 Yang Lv , Zefang Wang , Yu Jin , Mingtao Cao , Liang Han , Pei Zhang , Hongrong Li , Hong Gao , Fuli Li

Dirac electrons in graphene have a valley degree of freedom that is being explored as a carrier of information. In that context of "valleytronics" one seeks to coherently manipulate the valley index. Here we show that reflection from a…

Mesoscale and Nanoscale Physics · Physics 2018-09-12 C. W. J. Beenakker , N. V. Gnezdilov , E. Dresselhaus , V. P. Ostroukh , Y. Herasymenko , I. Adagideli , J. Tworzydlo

Bilayer graphene (two coupled graphitic monolayers arranged according to Bernal stacking) is a two-dimensional gapless semiconductor with a peculiar electronic spectrum different from the Dirac spectrum in the monolayer material. In…

Mesoscale and Nanoscale Physics · Physics 2007-05-23 K. Kechedzhi , Vladimir I. Fal'ko , E. McCann , B. L. Altshuler

We develop the theory of the spin and valley Hall effects in two-dimensional systems caused by asymmetric -- skew -- scattering of the quasiparticles. The collision integral is derived in the third order in the particle-particle interaction…

Mesoscale and Nanoscale Physics · Physics 2022-12-14 M. M. Glazov , L. E. Golub