Csaba Géza Péterfalvi

Publications (7) View all

• Article: Tuning the Thermoelectric Performance of Benzo-difuran Molecular Wires

  Csaba G. Péterfalvi, Iain Grace, Dávid Zs. Manrique, Colin J. Lambert
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  ABSTRACT: Using a first principles approach to electron transport, we calculate the electrical and thermoelectrical transport properties of a series of molecular wires containing benzo-difuran subunits. The presence of side groups in these structures introduces Fano resonances into the transport properties, which are not present in the more widely studied oligophenylene ethynylene and oligophenylene vinylene (OPE, OPV) molecules. We demonstrate that the energies of Fano resonances can be tuned by varying the electronegativity of selected atoms. We also study the relative effect of single, double or triple bonds along the molecular backbone and find that single bonds yield the highest thermopower, which at room temperature is approximately 22$\mu$V/K, which is comparable with the highest measured values for single-molecule thermopower reported to date.
  05/2013;
• Article: Suppression of single-molecule conductance fluctuations using extended anchor groups on graphene and carbon-nanotube electrodes

  Csaba G. Péterfalvi, Colin J. Lambert
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  ABSTRACT: Devices formed from single molecules attached to noble-metal electrodes exhibit large conductance fluctuations, which inhibit their development as reproducible functional units. We demonstrate that single molecules with planar anchor groups attached to carbon-based electrodes are more resilient to atomic-scale variation in the contacts and exhibit significantly lower conductance fluctuations. We examine the conductance of a 2,6-dibenzylamino core-substituted naphthalenediimide chromophore attached to carbon electrodes by either phenanthrene anchors or more extended anchor groups, which include oligophenylene ethynylene spacers. We demonstrate that for the more spatially extended anchor groups conductance fluctuations are significantly reduced. The current-voltage characteristic arising from long-range tunneling is found to be strongly nonlinear with pronounced conductance suppression below a threshold voltage of approximately 2.5 V.
  Physical Review B. 08/2012; 86(8):085443.
• Source

  Available from: József Cserti

  Article: Catastrophe optics of caustics in single and bilayer graphene: fine structure of caustics

  Csaba Péterfalvi, András Pályi, Ádám Rusznyák, János Koltai, József Cserti
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  ABSTRACT: We theoretically study the scattering of a plane wave of a ballistic electron on a circular n-p junction in single and bilayer graphene. We compare the exact wave function inside the junction to that obtained from a semiclassical formula developed in catastrophe optics. In the semiclassical picture short-wavelength electrons are treated as rays of particles that can get reflected and refracted at the n-p junction according to Snell's law with negative refraction index. We show that for short wavelength and close to caustics this semiclassical approximation gives good agreement with the exact results in the case of single-layer graphene. We also verify the universal scaling laws that govern the shrinking rate and intensity divergence of caustics in the semiclassical limit. It is straightforward to generalize our semiclassical method to more complex geometries, offering a way to efficiently design and model graphene-based electron-optical systems.
  05/2010;
• Source

  Available from: Csaba Géza Péterfalvi

  Article: Caustics due to a negative refractive index in circular graphene p-n junctions.

  József Cserti, András Pályi, Csaba Péterfalvi
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  ABSTRACT: We show that the wave functions form caustics in circular graphene p-n junctions which in the framework of geometrical optics can be interpreted with a negative refractive index.
  Physical Review Letters 01/2008; 99(24):246801. · 7.37 Impact Factor
• Article: Intraband electron focusing in bilayer graphene

  Csaba G. Péterfalvi, László Oroszlány, Colin J. Lambert, József Cserti
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  ABSTRACT: We propose an implementation of a valley selective electronic Veselago lens in bilayer graphene. We demonstrate that in the presence of an appropriately oriented potential step, low-energy electrons radiating from a point source can be re-focused coherently within the same band. The phenomenon is due to the trigonal warping of the band structure that leads to a negative refraction index. We show that the interference pattern can be controlled by an external mechanical strain.
  03/2012;