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

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Electron interferometry with a Quantum Point Contact: Effect of electron-electron
interaction and temperature
Andrii Kleshchonok, Geneviève Fleury, Jean-Louis Pichard
Service de Physique de l’Etat Condensé, IRAMIS / SPEC, CEA Saclay, 91191 Gif-sur-
Yvette, France
Motivated by experiments recently made in Harvard [1], Stanford [2], Zurich [3] and Grenoble
[4], we study a simplified model for describing an electron interferometer formed with a
quantum point contact and the depletion region induced by the charged tip of a scanning
gate microscope. The contact is made of a single site with Hubbard interaction U (Anderson
impurity) coupling two semi-infinite square lattices. A local moment [5] can take place in the
contact above the Kondo temperature. We study how this moment can be manipulated when
one scans the tip around the contact. We discuss also how the conductance of this
interferometer depends on the location the tip, on the strength U of the interaction and on the
temperature, in regimes where the Hartree-Fock approximation remains valid [6]. In certain
cases, an enhancement of the interference fringes can be yielded by an increase of the
temperature [7] or an increase of the strength U of the interaction.
[1] M.A. Topinka, et al. Coherent Branched Flow in a Two-Dimensional Electron Gas, Nature
410 183 (2001)
[2] M. P. Jura, et al. Unexpected features of branched flow through high-mobility twodimensional
electron gases , Nature Physics 3 841-845 (2007)
[3] A. A. Kozikov, et al. Interference of electrons in backscattering through a quantum point
contact, arXiv:1206.1371v1
[4] M. G.Pala , et al. Scanning gate microscopy of quantum rings: effects of an external
magnetic field and of charged defects, Nanotechnology 20, 26 (2009)
[5] Anderson P. W. Localized Magnetic States in Metals, Physical Review 124 41-53 (1961)
[6] Tsvelick A. M., Wiegmann P. B. Exact results in the theory of magnetic alloys, Advances
in Physics 32 453 (1983)
[7] About A., Lemarié G., Pichard J.-L. Thermal Enhancement of Interference Effects in
Quantum Point Contacts Phys. Rev. Lett. 106 156810 (2011)
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Symmetry-induced interference effects in metalloporphyrins wires
R.Ferradás 1,2 , V.M.García-Suárez 1,2,3 and J.Ferrer 1,2,3
1
Departamento de Física, Universidad de Oviedo, 33007 Oviedo, Spain
2
Nanomaterials and Nanotechnology Research Center, CSIC-Universidad de Oviedo, Spain
3
Department of Physics, Lancaster University, Lancaster LA1 4YW, United Kingdom
Organo-metallic molecular structures where a single metallic atom is embedded in the
organic backbone are ideal systems to study the effect of strong correlations on their
electronic structure. In this work we calculate the electronic and transport properties of a
series of metalloporphyrin molecules sandwiched by gold electrodes using a combination of
density functional theory and scattering theory. The impact of strong correlations at the
central metallic atom is gauged by comparing our results obtained using conventional DFT
and DFT+U approaches. The zero bias transport properties may or may not show spinfiltering
behavior, depending on the nature of the d state closest to the Fermi energy. The
type of d state depends on the metallic atom and gives rise to interference effects that
produce different Fano features. The inclusion of the U term opens a gap between the d
states and changes qualitatively the conductance and spin-filtering behavior in some of the