nanoelectronics - Institut d'Études Scientifiques de Cargèse (IESC)
nanoelectronics - Institut d'Études Scientifiques de Cargèse (IESC) nanoelectronics - Institut d'Études Scientifiques de Cargèse (IESC)
Friday conductivity does not necessarily imply a vanishing spin Hall effect. We also discuss the situation in which extrinsic spin orbit from impurities is present and the bulk spin Hall conductivity can be different from zero. [1] C. Gorini, R. Raimondi, P. Schwab, arXiv:1207.1289 __________________________________________________________________________ Spin-orbit coupling assisted by flexural phonons in graphene H. Ochoa (1) , A. H. Castro Neto (2,3) , V. I. Fal'ko (4,5) , F. Guinea (1) (1) Instituto de Ciencia de Materiales de Madrid. CSIC. Sor Juana Inés de la Cruz 3. 28049 Madrid. Spain. (2) Graphene Research Centre and Physics Department, National University of Singapore, 2 Science Drive 3, 117542, Singapore. (3) Department of Physics, Boston University, 590 Commonwealth Ave., Boston MA 02215, USA. (4) Physics Department, Lancaster University, Lancaster, LA1 4YB, UK. (5) DPMC, University of Geneva, 24 Quai Ernest-Ansermet, CH1211 Geneve 4, Switzerland We present a complete analysis of the possible couplings between spins and flexural, out of plane, vibrations [1]. From tight-binding models we obtain analytical and numerical estimates of their strength. We show that dynamical effects, induced by quantum and thermal fluctuations, significantly enhance the spin-orbit gap. We also compute the spin relaxation rates due to flexural phonon scattering. Our results confirm that graphene is an excellent candidate for spintronics devices. [1] H. Ochoa, A. H. Castro Neto, V. I. Fal'ko, F. Guinea, Spin-orbit coupling assisted by flexural phonons in graphene, arXiv:1209.4382 [cond-mat.mes-hall] __________________________________________________________________________ Massless Dirac bosons in honeycomb plasmonic lattices G. Weick, 1 C. Woollacott, 2 W.L. Barnes, 3 O. Hess, 4 E. Mariani 2 1 Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg & CNRS 2 Centre for Graphene Science, School of Physics, University of Exeter 3 School of Physics, University of Exeter 4 The Blackett Laboratory, Department of Physics, Imperial College London We consider a two-dimensional honeycomb lattice of metallic nanoparticles, each supporting a localized surface plasmon, and study the properties of the collective plasmons resulting from the near field dipolar interaction between the nanoparticles. We analytically investigate the dispersion, the effective Hamiltonian and the eigenstates of the collective plasmons for an arbitrary orientation of the individual dipole moments. When the polarization points close to the normal to the plane the spectrum presents Dirac cones, similar to those present in the electronic band structure of graphene. Moreover, we show that the corresponding eigenstates of the collective plasmons represent Dirac-like massless bosonic excitations. We further discuss how one can manipulate the Dirac points in the Brillouin zone and open a gap in the collective plasmon dispersion by modifying the polarization of the localized surface plasmons, paving the way for a fully tunable plasmonic analogue of graphene.
Friday Electron focusing in grapheme Csaba Péterfalvi 1,2 , László Oroszlány 1 , József Cserti 1 , Colin Lambert 2 1 Department of Physics of Complex Systems, Eötvös University, Budapest, H-1117, Hungary 2 Department of Physics, Lancaster University, Lancaster, LA1 4YB, UK We propose an implementation of a valley selective electronic Veselago lens, as a planar potential step in bilayer graphene. We demonstrate that low energy electrons radiating from a point source and being scattered by an appropriately oriented potential step can be focused again coherently within the same band. The phenomenon is due to the negative refraction index which is a consequence of the anisotropy in the dispersion relation caused by the trigonal warping effect. We also consider an effective Hamiltonian in which the electron-electron interaction [1], as well as external mechanical strain [2] is taken into account, and we show how this affects the focusing phenomenon. Recent studies on the electron-phonon interaction in bilayer graphene [3] suggest that the electrons' free path can be long enough even on room temperatures to enable the focusing. [1] Y. Lemonik, I. L. Aleiner, C. Toke, and V. I. Fal’ko, Spontaneous symmetry breaking and Lifshitz transition in bilayer graphene, Phys. Rev. B 82, 201408 (2010) [2] M. Mucha-Kruczyński, I. L. Aleiner and V. I. Fal’ko, Strained bilayer graphene: Band structure topology and Landau level spectrum, Phys. Rev. B 84, 041404 (2011) [3] K. M. Borysenko, J. T. Mullen, X. Li, Y. G. Semenov et al, Electron-phonon interactions in bilayer graphene, Phys. Rev. B 83, 161402 (2011) __________________________________________________________________________ Theory of scanning gate microscopy C. Gorini 1 , R. A. Jalabert 1 , W. Szewc 1 , S. Tomsovic 2 and D. Weinmann 1 1 Institut de Physique et Chimie des Matérieux de Strasbourg, UMR 7504, CNRS-UdS, 23 rue du Loess, BP 43, 67034 Strasbourg Cedex 2, France 2 Department of Physics and Astronomy, PO Box 642814, Washington State University, Pullman, WA 99164-2814, USA The conductance change due to a local perturbation in a phase-coherent nanostructure is calculated [1]. The general expressions to first and second order in the perturbation are applied to the scanning gate microscopy of a two-dimensional electron gas containing a quantum point contact. The relation between the conductance change and the local current density is discussed relying on an extension of the Szafer-Stone model for a constriction [2]. [1] R. A. Jalabert, W. Szewc, S. Tomsovic and D. Weinmann, What is measured in the scanning gate microscopy of a quantum point contact? Phys. Rev. Lett. 105 166802 (2010) [2] A. Szafer and A. D. Stone, Theory of Quantum Conduction through a Constriction Phys. Rev. Lett. 62 300 (1989)
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Friday<br />
conductivity does not necessarily imply a vanishing spin Hall effect. We also discuss the<br />
situation in which extrinsic spin orbit from impurities is present and the bulk spin Hall<br />
conductivity can be different from zero.<br />
[1] C. Gorini, R. Raimondi, P. Schwab, arXiv:1207.1289<br />
__________________________________________________________________________<br />
Spin-orbit coupling assisted by flexural phonons in graphene<br />
H. Ochoa (1) , A. H. Castro Neto (2,3) , V. I. Fal'ko (4,5) , F. Guinea (1)<br />
(1)<br />
<strong>Institut</strong>o <strong>de</strong> Ciencia <strong>de</strong> Materiales <strong>de</strong> Madrid. CSIC. Sor Juana Inés <strong>de</strong> la Cruz 3. 28049<br />
Madrid. Spain.<br />
(2)<br />
Graphene Research Centre and Physics Department, National University of Singapore, 2<br />
Science Drive 3, 117542, Singapore.<br />
(3)<br />
Department of Physics, Boston University, 590 Commonwealth Ave., Boston MA 02215,<br />
USA.<br />
(4)<br />
Physics Department, Lancaster University, Lancaster, LA1 4YB, UK.<br />
(5)<br />
DPMC, University of Geneva, 24 Quai Ernest-Ansermet, CH1211 Geneve 4, Switzerland<br />
We present a complete analysis of the possible couplings between spins and flexural, out of<br />
plane, vibrations [1]. From tight-binding mo<strong>de</strong>ls we obtain analytical and numerical estimates<br />
of their strength. We show that dynamical effects, induced by quantum and thermal<br />
fluctuations, significantly enhance the spin-orbit gap. We also compute the spin relaxation<br />
rates due to flexural phonon scattering. Our results confirm that graphene is an excellent<br />
candidate for spintronics <strong>de</strong>vices.<br />
[1] H. Ochoa, A. H. Castro Neto, V. I. Fal'ko, F. Guinea, Spin-orbit coupling assisted by<br />
flexural phonons in graphene, arXiv:1209.4382 [cond-mat.mes-hall]<br />
__________________________________________________________________________<br />
Massless Dirac bosons in honeycomb plasmonic lattices<br />
G. Weick, 1 C. Woollacott, 2 W.L. Barnes, 3 O. Hess, 4 E. Mariani 2<br />
1<br />
<strong>Institut</strong> <strong>de</strong> Physique et Chimie <strong>de</strong>s Matériaux <strong>de</strong> Strasbourg, Université <strong>de</strong> Strasbourg &<br />
CNRS<br />
2<br />
Centre for Graphene Science, School of Physics, University of Exeter<br />
3<br />
School of Physics, University of Exeter<br />
4<br />
The Blackett Laboratory, Department of Physics, Imperial College London<br />
We consi<strong>de</strong>r a two-dimensional honeycomb lattice of metallic nanoparticles, each supporting<br />
a localized surface plasmon, and study the properties of the collective plasmons resulting<br />
from the near field dipolar interaction between the nanoparticles. We analytically investigate<br />
the dispersion, the effective Hamiltonian and the eigenstates of the collective plasmons for<br />
an arbitrary orientation of the individual dipole moments. When the polarization points close<br />
to the normal to the plane the spectrum presents Dirac cones, similar to those present in the<br />
electronic band structure of graphene. Moreover, we show that the corresponding<br />
eigenstates of the collective plasmons represent Dirac-like massless bosonic excitations. We<br />
further discuss how one can manipulate the Dirac points in the Brillouin zone and open a gap<br />
in the collective plasmon dispersion by modifying the polarization of the localized surface<br />
plasmons, paving the way for a fully tunable plasmonic analogue of graphene.
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