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Search Results: 1 - 10 of 219493 matches for " C. Zoth "
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Aislamiento y caracterización del virus de la diarrea viral bovina en un ternero con síndrome purpúrico
Gollán,A; Chimeno Zoth,S A; Piccone,M E; Mari?o,B; Peralta,C; Rodríguez Armesto,R; Occhi,H;
Archivos de medicina veterinaria , 2006, DOI: 10.4067/S0301-732X2006000200011
Abstract: the bovine viral diarrhea (bvdv) virus causes numerous pathologies that range from reproductive losses to infections of little clinical significance in the bovine digestive tract. variation have been reported among the strains of the bvdv, which are classified into two biotypes; cytopathogenic (cp) and non-cytopathogenic (ncp), and the viral types i and ii. this work describes the pathological findings in a calf with diarrhea and severe thrombocytopenia. the strain isolated (334/3) was molecularly characterized by sequencing of the 5?non-coding region (5? ncr). these analyses revealed 90-98% homologies with reference strains type i strains and the changes associated with bvdv type ii, were not found.
Circular ac Hall Effect
J. Karch,P. Olbrich,M. Schmalzbauer,C. Zoth,C. Brinsteiner,M. Fehrenbacher,U. Wurstbauer,M. M. Glazov,S. A. Tarasenko,E. L. Ivchenko,D. Weiss,J. Eroms,R. Yakimova,S. Lara-Avila,S. Kubatkin,S. D. Ganichev
Physics , 2010,
Abstract: We report the observation of the circular ac Hall effect where the current is solely driven by the crossed ac electric and magnetic fields of circularly polarized radiation. Illuminating an unbiased monolayer sheet of graphene with circularly polarized terahertz radiation at room temperature generates - under oblique incidence - an electric current perpendicular to the plane of incidence, whose sign is reversed by switching the radiation helicity. Alike the classical dc Hall effect, the voltage is caused by crossed electric and magnetic fields which are however rotating with the light's frequency.
Spin-polarized electric currents in diluted magnetic semiconductor heterostructures induced by terahertz and microwave radiation
P. Olbrich,C. Zoth,P. Lutz,C. Drexler,V. V. Bel'kov,Ya. V. Terent'ev,S. A. Tarasenko,A. N. Semenov,S. V. Ivanov,D. R. Yakovlev,T. Wojtowicz,U. Wurstbauer,D. Schuh,S. D. Ganichev
Physics , 2012, DOI: 10.1103/PhysRevB.86.085310
Abstract: We report on the study of spin-polarized electric currents in diluted magnetic semiconductor (DMS) quantum wells subjected to an in-plane external magnetic field and illuminated by microwave or terahertz radiation. The effect is studied in (Cd,Mn)Te/(Cd,Mg)Te quantum wells (QWs) and (In,Ga)As/InAlAs:Mn QWs belonging to the well known II-VI and III-V DMS material systems, as well as, in heterovalent AlSb/InAs/(Zn,Mn)Te QWs which represent a promising combination of II-VI and III-V semiconductors. Experimental data and developed theory demonstrate that the photocurrent originates from a spin-dependent scattering of free carriers by static defects or phonons in the Drude absorption of radiation and subsequent relaxation of carriers. We show that in DMS structures the efficiency of the current generation is drastically enhanced compared to non-magnetic semiconductors. The enhancement is caused by the exchange interaction of carrier spins with localized spins of magnetic ions resulting, on the one hand, in the giant Zeeman spin-splitting, and, on the other hand, in the spin-dependent carrier scattering by localized Mn2+ ions polarized by an external magnetic field.
Spin polarized electric currents in semiconductor heterostructures induced by microwave radiation
C. Drexler,V. V. Bel'kov,B. Ashkinadze,P. Olbrich,C. Zoth,V. Lechner,Ya. V. Terent'ev,D. R. Yakovlev,G. Karczewski,T. Wojtowicz,D. Schuh,W. Wegscheider,S. D. Ganichev
Physics , 2010, DOI: 10.1063/1.3507896
Abstract: We report on microwave (mw) radiation induced electric currents in (Cd,Mn)Te/(Cd,Mg)Te and InAs/(In,Ga)As quantum wells subjected to an external in-plane magnetic field. The current generation is attributed to the spin-dependent energy relaxation of electrons heated by mw radiation. The relaxation produces equal and oppositely directed electron flows in the spin-up and spin-down subbands yielding a pure spin current. The Zeeman splitting of the subbands in the magnetic field leads to the conversion of the spin flow into a spin-polarized electric current.
Diluted magnetic semiconductor heterostructure AlSb/InAs/ZnMnTe with giant Zeeman effect for two dimensional electrons in InAs
Ya. V. Terent'ev,C. Zoth,V. V. Bel'kov,P. Olbrich,C. Drexler,V. Lechner,P. Lutz,A. N. Semenov,V. A. Solov'ev,I. V. Sedova,G. V. Klimko,T. A. Komissarova,S. V. Ivanov,S. D. Ganichev
Physics , 2011,
Abstract: A new approach to the growth of diluted magnetic semiconductors with two dimensional electron gas in InAs quantum well has been developed. The method is based on molecular-beam epitaxy of coherent "hybrid" AlSb/InAs/(Zn,Mn)Te heterostructures with a III-V/II-VI interface inside. The giant Zeeman splitting of the InAs conduction band caused by exchange interaction with Mn2+ ions has been proved by measuring the microwave radiation induced spin polarized electric currents.
Interplay of spin and orbital magnetogyrotropic photogalvanic effects in InSb/AlInSb quantum well structures
S. Stachel,P. Olbrich,C. Zoth,U. Hagner,T. Stangl,C. Karl,P. Lutz,V. V. Bel'kov,S. K. Clowes,T. Ashley,A. M. Gilbertson,S. D. Ganichev
Physics , 2011, DOI: 10.1103/PhysRevB.85.045305
Abstract: We report on the observation of linear and circular magnetogyrotropic photogalvanic effects in InSb/AlInSb quantum well structures. We show that intraband (Drude-like) absorption of terahertz radiation in the heterostructures causes a dc electric current in the presence of an in-plane magnetic field. The photocurrent behavior upon variation of the magnetic field strength, temperature and wavelength is studied. We show that at moderate magnetic fields the photocurrent exhibits a typical linear field dependence. At high magnetic fields, however, it becomes nonlinear and inverses its sign. The experimental results are analyzed in terms of the microscopic models based on asymmetric relaxation of carriers in the momentum space. We demonstrate that the observed nonlinearity of the photocurrent is caused by the large Zeeman spin splitting in InSb/AlInSb structures and an interplay of the spin-related and spin-independent roots of the magnetogyrotropic photogalvanic effect.
Cyclotron Resonance Assisted Photocurrents in Surface States of a 3D Topological Insulator Based on a Strained High Mobility HgTe Film
K. -M. Dantscher,D. A. Kozlov,P. Olbrich,C. Zoth,P. Faltermeier,M. Lindner,G. V. Budkin,S. A. Tarasenko,V. V. Belkov,Z. D. Kvon,N. N. Mikhailov,S. A. Dvoretsky,D. Weiss,B. Jenichen,S. D. Ganichev
Physics , 2015, DOI: 10.1103/PhysRevB.92.165314
Abstract: We report on the observation of cyclotron resonance induced photocurrents, excited by continuous wave terahertz radiation, in a 3D topological insulator (TI) based on an 80 nm strained HgTe film. The analysis of the photocurrent formation is supported by complimentary measurements of magneto-transport and radiation transmission. We demonstrate that the photocurrent is generated in the topologically protected surface states. Studying the resonance response in a gated sample we examined the behavior of the photocurrent, which enables us to extract the mobility and the cyclotron mass as a function of the Fermi energy. For high gate voltages we also detected cyclotron resonance (CR) of bulk carriers, with a mass about two times larger than that obtained for the surface states. The origin of the CR assisted photocurrent is discussed in terms of asymmetric scattering of TI surface carriers in the momentum space. Furthermore, we show that studying the photocurrent in gated samples provides a sensitive method to probe the effective masses and the mobility of 2D Dirac surface states, when the Fermi level lies in the bulk energy gap or even in the conduction band.
Quantum Oscillations of Photocurrents in HgTe Quantum Wells with Dirac and Parabolic Dispersions
C. Zoth,P. Olbrich,P. Vierling,K. -M. Dantscher,V. V. Bel'kov,M. A. Semina,M. M. Glazov,L. E. Golub,D. A. Kozlov,Z. D. Kvon,N. N. Mikhailov,S. A. Dvoretsky,S. D. Ganichev
Physics , 2014, DOI: 10.1103/PhysRevB.90.205415
Abstract: We report on the observation of magneto-oscillations of terahertz radiation induced photocurrent in HgTe/HgCdTe quantum wells (QWs) of different widths, which are characterized by a Dirac-like, inverted and normal parabolic band structure. The photocurrent data are accompanied by measurements of photoresistance (photoconductivity), radiation transmission, as well as magneto-transport. We develop a microscopic model of a cyclotron-resonance assisted photogalvanic effect, which describes main experimental findings. We demonstrate that the quantum oscillations of the photocurrent are caused by the crossing of Fermi level by Landau levels resulting in the oscillations of spin polarization and electron mobilities in spin subbands. Theory explains a photocurrent direction reversal with the variation of magnetic field observed in experiment. We describe the photoconductivity oscillations related with the thermal suppression of the Shubnikov-de Haas effect.
Giant spin-polarized current in a Dirac fermion system at cyclotron resonance
P. Olbrich,C. Zoth,P. Vierling,K. -M. Dantscher,G. V. Budkin,S. A. Tarasenko,V. V. Bel'kov,D. A. Kozlov,Z. D. Kvon,N. N. Mikhailov,S. A. Dvoretsky,S. D. Ganichev
Physics , 2013, DOI: 10.1103/PhysRevB.87.235439
Abstract: We report on the observation of the giant spin-polarized photocurrent in HgTe/HgCdTe quantum well (QW) of critical thickness at which a Dirac spectrum emerges. Exciting QW of 6.6 nm width by terahertz (THz) radiation and sweeping magnetic field we detected a resonant photocurrent. Remarkably, the position of the resonance can be tuned from negative (-0.4 T) to positive (up to 1.2 T) magnetic fields by means of optical gating. The photocurent data, accompanied by measurements of radiation transmission as well as Shubnikov-de Haas and quantum Hall effects, give an evidence that the enhancement of the photocurrent is caused by cyclotron resonance in a Dirac fermion system. The developed theory shows that the current is spin polarized and originates from the spin dependent scattering of charge carriers heated by the radiation.
Residual Metallic Contamination of Transferred Chemical Vapor Deposited Graphene
Grzegorz Lupina,Julia Kitzmann,Ioan Costina,Mindaugas Lukosius,Christian Wenger,Andre Wolff,Sam Vaziri,Mikael Ostling,Iwona Pasternak,Aleksandra Krajewska,Wlodek Strupinski,Satender Kataria,Amit Gahoi,Max C. Lemme,Guenther Ruhl,Guenther Zoth,Oliver Luxenhofer,Wolfgang Mehr
Physics , 2015, DOI: 10.1021/acsnano.5b01261
Abstract: Integration of graphene with Si microelectronics is very appealing by offering potentially a broad range of new functionalities. New materials to be integrated with Si platform must conform to stringent purity standards. Here, we investigate graphene layers grown on copper foils by chemical vapor deposition and transferred to silicon wafers by wet etch and electrochemical delamination methods with respect to residual sub-monolayer metallic contaminations. Regardless of the transfer method and associated cleaning scheme, time-of-flight secondary ion mass spectrometry and total reflection x-ray fluorescence measurements indicate that the graphene sheets are contaminated with residual metals (copper, iron) with a concentration exceeding 10$^{13}$ atoms/cm$^{2}$. These metal impurities appear to be partly mobile upon thermal treatment as shown by depth profiling and reduction of the minority charge carrier diffusion length in the silicon substrate. As residual metallic impurities can significantly alter electronic and electrochemical properties of graphene and can severely impede the process of integration with silicon microelectronics these results reveal that further progress in synthesis, handling, and cleaning of graphene is required on the way to its advanced electronic and optoelectronic applications.
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