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  • 51.
    Sekretareva, Alina
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemiska och optiska sensorsystem. Linköpings universitet, Tekniska fakulteten.
    Vagin, Mikhail
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Volkov, Anton V.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Zozoulenko, Igor V.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Turner, Anthony
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biosensorer och bioelektronik. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Mats
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemiska och optiska sensorsystem. Linköpings universitet, Tekniska fakulteten.
    Screen printed microband array based biosensor for water monitoring2015Inngår i: The Frumkin Symposium, 2015Konferansepaper (Fagfellevurdert)
  • 52.
    Sekretareva, Alina
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemiska och optiska sensorsystem. Linköpings universitet, Tekniska fakulteten.
    Vagin, Mikhail Yu
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Volkov, Anton V.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Zozoulenko, Igor V.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Turner, Anthony P.F.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biosensorer och bioelektronik. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Mats.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemiska och optiska sensorsystem. Linköpings universitet, Tekniska fakulteten.
    Total phenol analysis of water using a laccase-based microsensor array2015Inngår i: Program of the XXIII International Symposium on Bioelectrochemistry and Bioenergetics of the Bioelectrochemical Society. 14-18 June, 2015. Malmö, Sweden, Lausanne: Bioelectrochemical Society , 2015, s. 155-155Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The monitoring of phenolic compounds in raw waters and wastewaters is of great importance for environmental control. Use of biosensors for rapid, specific and simple detection of phenolic compounds is a promising approach. A number of biosensors have been developed for phenol detection. A general drawback of previously reported biosensors is their insufficient detection limits for phenols in water samples. One way to improve the detection limit is by the use of microelectrodes.

    Microband design of the microelectrodes combines convergent mass transport due to the microscale width and high output currents due to the macroscopic length. Among the various techniques available for microband electrode fabrication, we have chosen screen-printing which is a cost-effective production method.

    In this study, we report on the development of a laccase-based microscale biosensor operating under a convergent diffusion regime. Screen-printing followed by simple cutting was utilized for the fabrication of graphite microbands as a platform for further covalent immobilization of laccase. Numerical simulations, utilizing the finite element method with periodic boundary conditions, were used for modeling the voltammetric response of the developed microband electrodes. Anodization followed by covalent immobilization was used for the electrode modification with laccase. Direct and mediated laccase bioelectrocatalytic oxidation of phenols was studied on macro- and microscale graphite electrodes. Significant enhancement of the analytical performance was achieved by the establishment of convergent diffusion in the microscale sensor. Finally, the developed microsensor was utilized to monitor phenolic compounds in real waste water.

  • 53.
    Sekretaryova, Alina
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemiska och optiska sensorsystem. Linköpings universitet, Tekniska fakulteten.
    Volkov, Anton V.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Zozoulenko, Igor V.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Turner, Anthony
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biosensorer och bioelektronik. Linköpings universitet, Tekniska fakulteten.
    Vagin, Mikhail Yu
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Eriksson, Mats
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Kemiska och optiska sensorsystem. Linköpings universitet, Tekniska fakulteten.
    Total phenol analysis of weakly supported water using a laccase-based microband biosensor.2016Inngår i: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 907, s. 45-53Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The monitoring of phenolic compounds in wastewaters in a simple manner is of great importance for environmental control. Here, a novel screen printed laccase-based microband array for in situ, total phenol estimation in wastewaters and for water quality monitoring without additional sample pre-treatment is presented. Numerical simulations using the finite element method were utilized for the characterization of micro-scale graphite electrodes. Anodization followed by covalent modification was used for the electrode functionalization with laccase. The functionalization efficiency and the electrochemical performance in direct and catechol-mediated oxygen reduction were studied at the microband laccase electrodes and compared with macro-scale electrode structures. The reduction of the dimensions of the enzyme biosensor, when used under optimized conditions, led to a significant improvement in its analytical characteristics. The elaborated microsensor showed fast responses towards catechol additions to tap water – a weakly supported medium – characterized by a linear range from 0.2 to 10 μM, a sensitivity of 1.35 ± 0.4 A M−1 cm−2 and a dynamic range up to 43 μM. This enhanced laccase-based microsensor was used for water quality monitoring and its performance for total phenol analysis of wastewater samples from different stages of the cleaning process was compared to a standard method.

  • 54.
    Shylau, A A
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Klos, J W
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Zozoulenko, Igor
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Capacitance of graphene nanoribbons2009Inngår i: PHYSICAL REVIEW B, ISSN 1098-0121, Vol. 80, nr 20, s. 205402-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present an analytical theory for the gate electrostatics and the classical and quantum capacitance of the graphene nanoribbons (GNRs) and compare it with the exact self-consistent numerical calculations based on the tight-binding p-orbital Hamiltonian within the Hartree approximation. We demonstrate that the analytical theory is in a good qualitative (and in some aspects quantitative) agreement with the exact calculations. There are however some important discrepancies. In order to understand the origin of these discrepancies we investigate the self-consistent electronic structure and charge density distribution in the nanoribbons and relate the above discrepancy to the inability of the simple electrostatic model to capture the classical gate electrostatics of the GNRs. In turn, the failure of the classical electrostatics is traced to the quantum mechanical effects leading to the significant modification of the self-consistent charge distribution in comparison to the noninteracting electron description. The role of electron-electron interaction in the electronic structure and the capacitance of the GNRs is discussed. Our exact numerical calculations show that the density distribution and the potential profile in the GNRs are qualitatively different from those in conventional split-gate quantum wires; at the same time, the electron distribution and the potential profile in the GNRs show qualitatively similar features to those in the cleaved-edge overgrown quantum wires. Finally, we discuss an experimental extraction of the quantum capacitance from experimental data.

  • 55.
    Shylau, Artsem
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Zozoulenko, Igor
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Interacting electrons in graphene nanoribbons in the lowest Landau level2011Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, nr 7, s. 075407-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    e study the effect of electron-electron interaction and spin on electronic and transport properties of gated graphene nanoribbons (GNRs) in a perpendicular magnetic field in the regime of the lowest Landau level (LL). The electron-electron interaction is taken into account using the Hartree and Hubbard approximations, and the conductance of GNRs is calculated on the basis of the recursive Greens function technique within the Landauer formalism. We demonstrate that, in comparison to the one-electron picture, electron-electron interaction leads to the drastic changes in the dispersion relation and structure of propagating states in the regime of the lowest LL showing a formation of the compressible strip and opening of additional conductive channels in the middle of the ribbon. We show that the latter are very sensitive to disorder and get scattered even if the concentration of disorder is moderate. In contrast, the edge states transport is very robust and cannot be suppressed even in the presence of a strong spin-flipping.

  • 56.
    Shylau, Artsem
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Zozoulenko, Igor
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Xu, H
    University of Dusseldorf.
    Heinzel, T
    University of Dusseldorf.
    Generic suppression of conductance quantization of interacting electrons in graphene nanoribbons in a perpendicular magnetic field2010Inngår i: PHYSICAL REVIEW B, ISSN 1098-0121, Vol. 82, nr 12, s. 121410-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effects of electron interaction on the magnetoconductance of graphene nanoribbons (GNRs) are studied within the Hartree approximation. We find that a perpendicular magnetic field leads to a suppression instead of an expected improvement of the quantization. This suppression is traced back to interaction-induced modifications of the band structure leading to the formation of compressible strips in the middle of GNRs. It is also shown that the hard-wall confinement combined with electron interaction generates overlaps between forward and backward propagating states, which may significantly enhance backscattering in realistic GNRs. The relation to available experiments is discussed.

  • 57.
    Tarasov, A
    et al.
    University of Dusseldorf.
    Hugger, S
    University of Dusseldorf.
    Xu, Hengyi
    University of Dusseldorf.
    Cerchez, M
    University of Dusseldorf.
    Heinzel, T
    University of Dusseldorf.
    Zozoulenko, Igor
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Gasser-Szerer, U
    ETH, Zurich, Switzerland .
    Reuter, D
    Ruhr University Bochum.
    D Wieck, A
    Ruhr University Bochum.
    Quantized Magnetic Confinement in Quantum Wires2010Inngår i: PHYSICAL REVIEW LETTERS, ISSN 0031-9007, Vol. 104, nr 18, s. 186801-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ballistic quantum wires are exposed to longitudinal profiles of perpendicular magnetic fields composed of a spike and a homogeneous part. An asymmetric magnetoconductance peak as a function of the homogeneous magnetic field is found, comprising quantized conductance steps in the interval where the homogeneous magnetic field and the magnetic barrier have identical polarities, and a characteristic shoulder with several resonances in the interval of opposite polarities. The observations are interpreted in terms of inhomogeneous diamagnetic shifts of the quantum wire modes leading to magnetic confinement.

  • 58.
    Tvingstedt, Kristofer
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Rahachou, Aliaksandr
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Persson, Nils-Krister
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Zozoulenko, Igor V.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Surface plasmon increased absorption in polymer photovoltaic cells2007Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, nr 11, s. 113514 -Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The authors demonstrate the triggering of surface plasmons at the interface of a metal grating and a photovoltaic bulk heterojunction blend of alternating polyfluorenes and a fullerene derivative. An increased absorption originating from surface plasmon resonances is confirmed by experimental reflection studies and theoretical modeling. Plasmonic resonances are further confirmed to influence the extracted photocurrent from devices. More current is generated at the wavelength position of the plasmon resonance peak. High conductivity polymer electrodes are used to build inverted sandwich structures with top anode and bottom metal grating, facilitating for triggering and characterization of the surface plasmon effects.

  • 59.
    Vasko, F T
    et al.
    NAS Ukraine.
    Zozoulenko, Igor
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Conductivity of a graphene strip: Width and gate-voltage dependencies2010Inngår i: APPLIED PHYSICS LETTERS, ISSN 0003-6951, Vol. 97, nr 9, s. 092115-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the conductivity of a graphene strip taking into account electrostatically induced charge accumulation on its edges. Using a local dependency of the conductivity on the carrier concentration we find that the electrostatic size effect in doped graphene strip of the width of 0.5-3 mu m can result in a significant (about 40%) enhancement of the effective conductivity in comparison to the infinitely wide samples. This effect should be taken into account both in the device simulation as well as for verification of scattering mechanisms in graphene.

  • 60.
    Volkov, A. V.
    et al.
    Nizhny Novgorod State University, Russia.
    Shylau, Artsem
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    Zozoulenko, Igor
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    Interaction-induced enhancement of g-factor in graphene2012Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 86, nr 15, s. 155440-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the effect of electron interaction on the spin-splitting and the g-factor in graphene in perpendicular magnetic field using the Hartree and Hubbard approximations within the Thomas-Fermi model. We found that the g-factor is enhanced in comparison to its free electron value g = 2 and oscillates as a function of the filling factor ѵ in the range 2 ≤ g < 4 reaching maxima at even ѵ and minima at odd ѵ. We outline the role of charged impurities in the substrate, which are shown to suppress the oscillations of the g-factor. This effect becomes especially pronounced with the increase of the impurity concentration, when the effective g-factor becomes independent of the filling factor reaching a value of g ≈ 2.3. A relation to the recent experiment is discussed.

  • 61.
    Volkov, Anton
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    Tybrandt, Klas
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    Berggren, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    Zozoulenko, Igor
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    Modeling of Charge Transport in Ion Bipolar Junction Transistors2014Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, nr 23, s. 6999-7005Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Spatiotemporal control of the complex chemical microenvironment is of great importance to many fields within life science. One way to facilitate such control is to construct delivery circuits, comprising arrays of dispensing outlets, for ions and charged biomolecules based on ionic transistors. This allows for addressability of ionic signals, which opens up for spatiotemporally controlled delivery in a highly complex manner. One class of ionic transistors, the ion bipolar junction transistors (IBJTs), is especially attractive for these applications because these transistors are functional at physiological conditions and have been employed to modulate the delivery of neurotransmitters to regulate signaling in neuronal cells. Further, the first integrated complementary ionic circuits were recently developed on the basis of these ionic transistors. However, a detailed understanding of the device physics of these transistors is still lacking and hampers further development of components and circuits. Here, we report on the modeling of IBJTs using Poissons and Nernst-Planck equations and the finite element method. A two-dimensional model of the device is employed that successfully reproduces the main characteristics of the measurement data. On the basis of the detailed concentration and potential profiles provided by the model, the different modes of operation of the transistor are analyzed as well as the transitions between the different modes. The model correctly predicts the measured threshold voltage, which is explained in terms of membrane potentials. All in all, the results provide the basis for a detailed understanding of IBJT operation. This new knowledge is employed to discuss potential improvements of ion bipolar junction transistors in terms of miniaturization and device parameters.

  • 62.
    Xu, Hengyi
    et al.
    Condensed Matter Physics Laboratory, Heinrich-Heine-Universität, Universitätsstrasse 1, 40225 Düsseldorf, Germany.
    Heinzel, T.
    Condensed Matter Physics Laboratory, Heinrich-Heine-Universität, Universitätsstrasse 1, 40225 Düsseldorf, Germany.
    Evaldsson, Martin
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Ihnatsenka, Siarhei
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Zozoulenko, Igor
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Resonant reflection at magnetic barriers in quantum wires2007Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, nr 20, s. 205301-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The conductance of a quantum wire containing a single magnetic barrier is studied numerically by means of the recursive Green's function technique. For sufficiently strong and localized barriers, Fano-type reflection resonances are observed close to the pinch-off regime. They are attributed to a magnetoelectric vortex-type quasibound state inside the magnetic barrier that interferes with an extended mode outside. We, furthermore, show that disorder can substantially modify the residual conductance around the pinch-off regime.

  • 63.
    Xu, Hengyi
    et al.
    Heinrich-Heine-Universität.
    Heinzel, T.
    Heinrich-Heine-Universität.
    Evaldsson, Martin
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Zozoulenko, I. V.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Magnetic barriers in graphene nanoribbons: Theoretical study of transport properties2008Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 77, nr 24, s. 245401-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A theoretical study of the transport properties of zigzag and armchair graphene nanoribbons with a magnetic barrier on top is presented. The magnetic barrier modifies the energy spectrum of the nanoribbons locally, which results in an energy shift of the conductance steps toward higher energies. The magnetic barrier also induces Fabry–Pérot-type oscillations, provided the edges of the barrier are sufficiently sharp. The lowest propagating state present in zigzag and metallic armchair nanoribbons prevents confinement of the charge carriers by the magnetic barrier. Disordered edges in nanoribbons tend to localize the lowest propagating state, which get delocalized in the magnetic barrier region. Thus, in sharp contrast to the case of two-dimensional graphene, the charge carriers in graphene nanoribbons cannot be confined by magnetic barriers. We also present a method based on the Green's function technique for the calculation of the magnetosubband structure, Bloch states and magnetoconductance of the graphene nanoribbons in a perpendicular magnetic field. Utilization of this method greatly facilitates the conductance calculations, because, in contrast to existing methods, the present method does not require self-consistent calculations for the surface Green's function.

  • 64.
    Xu, Hengyi
    et al.
    University of Dusseldorf.
    Heinzel, T
    University of Dusseldorf.
    Shylau, Artsem A
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Zozoulenko, Igor
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Interactions and screening in gated bilayer graphene nanoribbons2010Inngår i: PHYSICAL REVIEW B, ISSN 1098-0121, Vol. 82, nr 11, s. 115311-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effects of Coulomb interactions on the electronic properties of bilayer graphene nanoribbons (BGNs) covered by a gate electrode are studied theoretically. The electron-density distribution and the potential profile are calculated self-consistently within the Hartree approximation. A comparison to their single-particle counterparts reveals the effects of interactions and screening. Due to the finite width of the nanoribbon in combination with electronic repulsion, the gate-induced electrons tend to accumulate along the BGN edges where the potential assumes a sharp triangular shape. This has a profound effect on the energy gap between electron and hole bands, which depends nonmonotonously on the gate voltage and collapses at intermediate electric fields. We interpret this behavior in terms of interaction-induced warping of the energy dispersion.

  • 65.
    Xu, Hengyi
    et al.
    University of Dusseldorf.
    Heinzel, T.
    University of Dusseldorf.
    Zozoulenko, Igor
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Conductivity and scattering in graphene bilayers: Numerically exact results versus Boltzmann approach2011Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, nr 11, s. 115409-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We derive analytical expressions for the conductivity of bilayer graphene (BLG) using the Boltzmann approach within the the Born approximation for a model of Gaussian disorders describing both short- and long-range impurity scattering. The range of validity of the Born approximation is established by comparing the analytical results to exact tight-binding numerical calculations. A comparison of the obtained density dependencies of the conductivity with experimental data shows that the BLG samples investigated experimentally so far are in the quantum scattering regime where the Fermi wavelength exceeds the effective impurity range. In this regime both short-and long-range scattering lead to the same linear density dependence of the conductivity. Our calculations imply that bilayer and single-layer graphene have the same scattering mechanisms. We also provide an upper limit for the effective, density-dependent spatial extension of the scatterers present in the experiments.

  • 66.
    Xu, Hengyi
    et al.
    University of Dusseldorf.
    Heinzel, T
    University of Dusseldorf.
    Zozoulenko, Igor
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Edge disorder and localization regimes in bilayer graphene nanoribbons2009Inngår i: PHYSICAL REVIEW B, ISSN 1098-0121, Vol. 80, nr 4, s. 045308-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A theoretical study of the magnetoelectronic properties of zigzag and armchair bilayer graphene nanoribbons (BGNs) is presented. Using the recursive Greens function method, we study the band structure of BGNs in uniform perpendicular magnetic fields and discuss the zero-temperature conductance for the corresponding clean systems. The conductance is quantized as 2(n+1)G(0) for the zigzag edges and nG(0) for the armchair edges with G(0) = 2e(2)/h being the conductance unit and n an integer. Special attention is paid to the effects of edge disorder. As in the case of monolayer graphene nanoribbons (GNR), a small degree of edge disorder is already sufficient to induce a transport gap around the neutrality point. We further perform comparative studies of the transport gap E-g and the localization length xi in bilayer and monolayer nanoribbons. While for the GNRs E-g(GNR) similar to 1/W, the corresponding transport gap E-g(BGN) for the bilayer ribbons shows a more rapid decrease as the ribbon width W is increased. We also demonstrate that the evolution of localization lengths with the Fermi energy shows two distinct regimes. Inside the transport gap, xi is essentially independent on energy and the states in the BGNs are significantly less localized than those in the corresponding GNRs. Outside the transport gap xi grows rapidly as the Fermi energy increases and becomes very similar for BGNs and GNRs.

  • 67.
    Xu, Hengyi
    et al.
    University of Dusseldorf.
    Heinzel, T
    University of Dusseldorf.
    Zozoulenko, Igor
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Electronic properties of quantum dots formed by magnetic double barriers in quantum wires2011Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, nr 3, s. 035319-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The transport through a quantum wire exposed to two magnetic spikes in series is modeled. We demonstrate that quantum dots can be formed this way which couple to the leads via magnetic barriers. Conceptually, all quantum dot states are accessible by transport experiments. The simulations show Breit-Wigner resonances in the closed regime, while Fano resonances appear as soon as one open transmission channel is present. The system allows one to tune the dots confinement potential from subparabolic to superparabolic by experimentally accessible parameters.

  • 68.
    Xu, Hengyi
    et al.
    University of Dusseldorf.
    Heinzel, Thomas
    University of Dusseldorf.
    Zozoulenko, Igor
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Geometric magnetoconductance dips by edge roughness in graphene nanoribbons2012Inngår i: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 97, nr 2, s. 28008-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The magnetoconductance of graphene nanoribbons with rough zigzag and armchair edges is studied by numerical simulations. Nanoribbons with sufficiently small bulk disorder show a pronounced magnetoconductance minimum at cyclotron radii close to the ribbon width, in close analogy to the wire peak observed in conventional semiconductor quantum wires. In zigzag nanoribbons, this feature becomes visible only above a threshold amplitude of the edge roughness, as a consequence of the reduced current density close to the edges.

  • 69.
    Zozoulenko, Igor
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Blomquist, T
    Time-resolved dynamics of electron wave packets in chaotic and regular quantum billiards with leads2003Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 67, nr 8Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We perform numerical studies of wave packet propagation through open quantum billiards whose classical counterparts exhibit regular and chaotic dynamics. We show that for tless than or similar totau(H)(tau(H) being the Heisenberg time), the features in the transmitted and reflected currents are directly related to specific classical trajectories connecting the billiard leads. When tgreater than or similar totau(H), the calculated quantum-mechanical current starts to deviate from its classical counterpart, with the decay rate obeying a power law that depends on the number of decay channels. In a striking contrast to the classical escape from chaotic and regular systems (exponentially fast e(-gammat) for the former versus power-law t(-xi) for the latter), the asymptotic decay of the corresponding quantum systems does not show a qualitative difference.

  • 70.
    Zozoulenko, Igor
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Evaldsson, Martin
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Quantum antidot as a controllable spin injector and spin filter2005Inngår i: International Conference on the Physics of Semiconductors,2004, Melville, New York: American Institute of Physics , 2005, s. 1395-Konferansepaper (Fagfellevurdert)
  • 71.
    Zozoulenko, Igor
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Ihnatsenka, Siarhei
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Electron interaction and spin effects in quantum wires, quantum dots and quantum point contacts: A first-principles mean-field approach2008Inngår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 20, nr 16Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have developed a mean-field first-principles approach for studying electronic and transport properties of low dimensional lateral structures in the integer quantum Hall regime. The electron interactions and spin effects are included within the spin density functional theory in the local density approximation where the conductance, the density, the effective potentials and the band structure are calculated on the basis of the Green's function technique. In this paper we present a systematic review of the major results obtained on the energetics, spin polarization, effective g factor, magnetosubband and edge state structure of split-gate and cleaved-edge overgrown quantum wires as well as on the conductance of quantum point contacts (QPCs) and open quantum dots. In particular, we discuss how the spin-resolved subband structure, the current densities, the confining potentials, as well as the spin polarization of the electron and current densities in quantum wires and antidots evolve when an applied magnetic field varies. We also discuss the role of the electron interaction and spin effects in the conductance of open systems focusing our attention on the 0.7 conductance anomaly in the QPCs. Special emphasis is given to the effect of the electron interaction on the conductance oscillations and their statistics in open quantum dots as well as to interpretation of the related experiments on the ultralow temperature saturation of the coherence time in open dots. © 2008 IOP Publishing Ltd.

  • 72.
    Zozoulenko, Igor
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    Ihnatsenka, Siarhei
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska högskolan.
    Hysteresis and spin phase transitions in quantum wires in the integer quantum Hall regime2007Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, nr 3, s. 035318-1-035318-5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We demonstrate that a split-gate quantum wire in the integer quantum Hall regime can exhibit electronic transport hysteresis for up- and down-sweeps of a magnetic field. This behavior is shown to be due to phase spin transitions between two different ground states with and without spatial spin polarization in the vicinity of the wire boundary. The observed effect has a many-body origin arising from an interplay between a confining potential, Coulomb interactions, and the exchange interaction. We also demonstrate and explain why the hysteretic behavior is absent for steep and smooth confining potentials and is present only for a limited range of intermediate confinement slopes. © 2007 The American Physical Society.

  • 73.
    Zozoulenko, Igor
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Ihnatsenka, Siarhei
    ITN Linköpings universitet.
    Quenching of compressible edge states around antidots2006Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, nr 20, s. 201303-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We provide a systematic quantitative description of the edge state structure around a quantum antidot in the integer quantum Hall regime. The calculations for spinless electrons within the Hartree approximation reveal that the widely used Chklovskii electrostatic description [Phys. Rev. B 46, 4026 (1992)] greatly overestimates the widths of the compressible strips, the difference between these approaches diminishes as the size of the antidot increases. By including spin effects within density functional theory in the local spin-density approximation, we demonstrate that the exchange interaction can suppress the formation of compressible strips and lead to a spatial separation between the spin-up and spin-down states. As the magnetic field increases, the outermost compressible strip related to spin-down states starts to form. However, in striking contrast to quantum wires, the innermost compressible strip (due to spin-up states) never develops for antidots. © 2006 The American Physical Society.

  • 74.
    Zozoulenko, Igor
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Ihnatsenka, Siarhei
    ITN Linköpings universitet.
    Spatial spin polarization and suppression of compressible edge channels in the integer quantum Hall regime2006Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 73, nr 15, s. 155314-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We perform systematical numerical studies of the structure of spin-resolved compressible strips in split-gate quantum wires taking into account the exchange and correlation interaction within the density functional theory in the local spin-density approximation. We find that for realistic parameters of the wire the exchange interaction can completely suppress the formation of the compressible strips. As the depletion length or magnetic field are increased, the compressible strips starts to form first for the spin-down and then for spin-up edge channels. We demonstrate that the widths of these strips plus the spatial separation between them caused by the exchange interaction is equal to the width of the compressible strip calculated in the Hartree approximation for spinless electrons. We also discuss the effect of electron density on the suppression of the compressible strips in quantum wires. © 2006 The American Physical Society.

  • 75.
    Zozoulenko, Igor
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Ihnatsenka, Siarhei
    ITN Linköpings universitet.
    Spin polarization of edge states and the magnetosubband structure in quantum wires2006Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 73, nr 7, s. 075331-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We provide a quantitative description of the structure of edge states in split-gate quantum wires in the integer quantum Hall regime. We develop an effective numerical approach based on the Green's function technique for the self-consistent solution of Schrödinger equation where electron and spin interactions are included within the density functional theory in the local spin density approximation. We use the developed method to calculate the subband structure and propagating states in the quantum wires in perpendicular magnetic field starting with a geometrical layout of the wire. We discuss how the spin-resolved subband structure, the current densities, the confining potentials, as well as the spin polarization of the electron and current densities evolve when an applied magnetic field varies. We demonstrate that the exchange and correlation interactions dramatically affect the magnetosubbands in quantum wires bringing qualitatively new features in comparison to a widely used model of spinless electrons in Hartree approximation. © 2006 The American Physical Society.

  • 76.
    Zozoulenko, Igor
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Rahachou, Aliaksandr
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Q factors and resonant states of whispering-gallery-mode dielectric microdisk cavities for lasing applications2005Inngår i: Proceedings of SPIE, ISSN 0361-0748, Vol. 5708, s. 210-221Artikkel i tidsskrift (Fagfellevurdert)
  • 77.
    Zozoulenko, Igor
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Sachrajda, A.S.
    Inst. for Microstructural Science, National Research Council, Montreal Road, Ottawa, Ont. K1A 0R6, Canada.
    Gould, C.
    Inst. for Microstructural Science, National Research Council, Montreal Road, Ottawa, Ont. K1A 0R6, Canada, Dépt. de Physique and CRPS, Université de Sherbrooke, Sherbrooke, Que. J1K 2R1, Canada.
    Berggren, Karl-Fredrik
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Zawadzki, P.
    Inst. for Microstructural Science, National Research Council, Montreal Road, Ottawa, Ont. K1A 0R6, Canada.
    Feng, Y.
    Inst. for Microstructural Science, National Research Council, Montreal Road, Ottawa, Ont. K1A 0R6, Canada.
    Wasilewski, Z.
    Inst. for Microstructural Science, National Research Council, Montreal Road, Ottawa, Ont. K1A 0R6, Canada.
    Magnetoconductance of a few-electron open quantum dot2000Inngår i: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 6, nr 1, s. 409-413Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Magnetoconductance of a small open lateral dot is studied both theoretically and experimentally for the conditions when the dot contains down to approximately 15 electrons. We confirm the existence of a new regime for open dots in which the transport through the structure occurs through individual eigenstates of the corresponding closed dot. In particular, at low magnetic fields the characteristic features in the conductance are related to the underlying eigenspectrum shells. When the number of modes in the leads is reduced more detailed structures within the shells due to single eigenlevels becomes discernible. At higher fields Landau level condensation is evident as well as the crossing of levels collapsing to the different Landau levels.

  • 78.
    Zozoulenko, Igor V.
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Evaldsson, Martin
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska högskolan.
    Quantum antidot as a controllable spin injector and spin filter2004Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 85, nr 15, s. 3136-3138Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We propose a device based on an antidot embedded in a narrow quantum wire in the edge-state regime, that can be used to inject and/or control spin-polarized current. The operational principle of the device is based on the effect of resonant backscattering from one edge state into another through localized quasibound states, combined with the effect of Zeeman splitting of the quasibound states in sufficiently high magnetic field. We outline the device geometry, present detailed quantum-mechanical transport calculations, and suggest a possible scheme to test the device performance and functionality.

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