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Thursday Andreev reflection from a topological superconductor with chiral symmetry M. Diez, J. P. Dahlhaus, M. Wimmer, C. W. J. Beenakker Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, 2300 RA Leiden, The Netherlands Chiral symmetry (H -> -H if e h) of the Hamiltonian of electron-hole (e-h) excitations in an N-mode superconducting wire is associated with a topological quantum number Q ∈ Z (symmetry class BDI). In Ref. [1] we show that Q=Tr(r he ) equals the trace of the matrix of Andreev reflection amplitudes, providing a link with the electrical conductance G. We derive G=(2e 2 /h)|Q| for |Q|=N,N-1, and more generally provide a Q-dependent upper and lower bound on G. We calculate the probability distribution P(G) for chaotic scattering, in the circular ensemble of random-matrix theory, to obtain the Q-dependence of weak localization and mesoscopic conductance fluctuations. We investigate the effects of chiral symmetry breaking by spin-orbit coupling of the transverse momentum (causing a class BDI-to-D crossover), in a model of a disordered semiconductor nanowire with induced superconductivity. For wire widths less than the spin-orbit coupling length, the conductance as a function of chemical potential can show a sequence of 2e 2 /h steps - insensitive to disorder. [1] M. Diez, J. P. Dahlhaus, M. Wimmer, C. W. J. Beenakker, Andreev reflection from a topological superconductor with chiral symmetry, Phys. Rev. B 86 094501 (2012) __________________________________________________________________________ Zero-bias conductance peak from weak antilocalization in a Majorana nanowire Dmitry I. Pikulin*, J. P. Dahlhaus*, M. Wimmer*, H. Schomerus', and C. W. J. Beenakker* *Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, 2300 RA Leiden, The Netherland, 'Department of Physics, Lancaster University, Lancaster, LA1 4YB, United Kingdom We show [1] that weak antilocalization by disorder coexists with resonant Andreev reflection by Majorana zero-mode, both producing zero-voltage conductance peak of order e 2 /h in a superconducting nanowire. The peak is widely believed to be the smoking gun signature of the Majorana zero-mode [2], its observation has been reported [3]. We identify methods to distinguish the Majorana resonance from the weak antilocalization effect. [1] D. I. Pikulin, J. P. Dahlhaus, M. Wimmer, H. Schomerus, and C. W. J. Beenakker, arXiv 1206.6687 (2012) [2] K. T. Law, P. A. Lee, and T. K. Ng, Phys. Rev. Lett. 103, 237001 (2009) [3] V. Mourik, K. Zuo, S. M. Frolov, R. Plissard, E. P. A.M. Bakkers, and L. P. Kouwenhoven, Science 336, 1003 (2012); M. T. Deng, C. L. Yu, G. Y. Huang, M. Larsson, P. Caroff, and H. Q. Xu, arXiv:1204.4130 (2012); A. Das, Y. Ronen, Y. Most, Y. Oreg, M. Heiblum, and H. Shtrikman, arXiv:1205.7073 (2012)
Thursday Electronic standing waves on the surface of the topological insulator Bi 2 Te 3 P.Rakyta 1 , A.Pályi 2 , J.Cserti 1 1 Department of Physics of Complex Systems, Eötvös University, H-1117 Budapest, Pázmány Péter sétány 1/A, Hungary 2 Department of Materials Physics, Eötvös University, H-1117 Budapest, Pázmány Péter sétány 1/A, Hungary A line defect on a metallic surface induces standing waves in the electronic local density of states (LDOS). Asymptotically far from the defect, the wave number of the LDOS oscillations at the Fermi energy is usually equal to the distance between nesting segments of the Fermi contour, and the envelope of the LDOS oscillations shows a power-law decay as moving away from the line defect. Here, we theoretically analyze the LDOS oscillations close to a line defect on the surface of the topological insulator Bi 2 Te 3 , and identify an important preasymptotic contribution with wave-number and decay characteristics markedly different from the asymptotic contributions. The calculated energy dependence of the wave number of the preasymptotic LDOS oscillations is in quantitative agreement with the result of a recent scanning tunneling microscopy experiment [1]. [1] Z.Alpichshev, J.G.Analytis, J.-H.Chu, I.R.Fisher, Y.L.Chen, Z.X.Shen, A.Fang and A.Kapitulnik, Phys. Rev. Lett. 104, 016401 (2010) __________________________________________________________________________ How does Exact DFT compares with exact solutions in simple models of strongly correlated electrons ? Jaime Ferrer, Diego Carrascal Departamento de Física, Universidad de Oviedo We present analytic expressions for the exact density functional and Kohn-Sham Hamiltonian of simple tight-binding models of correlated electrons. These are the single- and double-site versions of the Anderson, Hubbard and spinless fermion models. The exact exchange and correlation potentials keep the full non-local dependence on electron occupations. The analytic expressions allow to compare the Kohn-Sham eigenstates of exact density functional theory with the many-body quasi-particle states of these correlatedelectron systems. The exact Kohn-Sham spectrum describes correctly many of the non-trivial features of the many-body quasi-particle spectrum, as for example the precursors of the Kondo peak. However, we find that some pieces of the quasi-particle spectrum are missing because the many-body phase-space for electron and hole excitations is richer [1]. [1] D. Carrascal and J. Ferrer, Phys. Rev. B 85 045110 (2012)
Page 1 and 2: 2012 22 Octobre 27 Octobre WORKSHOP
Page 3 and 4: Afternoon Morning Timetable Monday
Page 5 and 6: 15h50 - 16h20 Coffee Break 16h20 -
Page 7 and 8: Monday Abstracts Monday, October 22
Page 9 and 10: Monday Single-Electron Tunneling an
Page 11 and 12: Tuesday Tuesday, October 23 Random-
Page 13 and 14: Tuesday the energy level spacings a
Page 15 and 16: Tuesday Electron refrigeration by n
Page 17 and 18: Wednesday [4] K. Saito, G. Benenti,
Page 19: Thursday [3] B. A. Bernevig, T. L.
Page 23 and 24: Friday Nanoscale inhomogeneities in
Page 25 and 26: Friday Electron focusing in graphem
Page 27 and 28: Friday molecules. We explain the or
Page 29 and 30: Posters Posters Ab-initio study of
Page 31 and 32: Posters Nonclassical photon-pair pr

nanoelectronics - Institut d'Études Scientifiques de Cargèse (IESC)

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