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The influence of a magnetic field on Landau levels (LLs) in graphene-based devices is described via the magnetooptical response induced by terahertz (THz) radiation. For single-layer graphene, the resonance energies of the transitions between the on Landau levels (LLs) such as L1, L2 and L3 fit quite well to the terahertz spectral range at low magnetic fields. Also, the calculations for the terahertz photoresponse (photoconductivity) in the presence of low magnetic fields, the reported calculations for the scattering rate of LLs, recent and our experimental results of photoresponse measurements yield that singlelayer graphene is suitable for the detection of terahertz radiation. [ABSTRACT FROM AUTHOR]

The competition between the Kondo effect and the Ruderman-Kittel-Kasuya-Yoshida (RKKY) interaction is investigated in a double quantum dots system, coupled via a central open conducting region. A perpendicular magnetic field induces the formation of Landau Levels which in turn give rise to the so-called Kondo chessboard pattern in the transport through the quantum dots. The two quantum dots become therefore chirally coupled via the edge channels formed in the open conducting area. In regions where both quantum dots exhibit Kondo transport the presence of the RKKY exchange interaction is probed by an analysis of the temperature dependence. The thus obtained Kondo temperature of one dot shows an abrupt increase at the onset of Kondo transport in the other, independent of the magnetic field polarity, i.e. edge state chirality in the central region. [ABSTRACT FROM AUTHOR]

For an InAs quantum dot we study the current shot noise at a Fermi-edge singularity in low temperature cross-correlation measurements. In the regime of the interaction effect the strong suppression of noise observed at zero magnetic field and the sequence of enhancement and suppression in magnetic field go beyond a Markovian master equation model. Qualitative and quantitative agreement can however be achieved by a generalized master equation model taking non-Markovian dynamics into account. [ABSTRACT FROM AUTHOR]

A lateral quantum dot with approx. 50 electrons is analyzed in high perpendicular magnetic fields. In a regime with two Landau levels (LL) in the quantum dot information about the spin structure is gained by investigating the position of Coulomb blockade peaks. A typical zig-zag pattern is observed which is roughly explained with the so called Constant Interaction model. However, only states from LL0 can be approximated with this model, while for LL1 more complex electron-electron interactions must be included. This is done with spin density functional theory calculations. As a result, full spin polarization is found for LL1, the so called spin droplet. [ABSTRACT FROM AUTHOR]

Twisted graphene monolayers form a sample of two closely spaced two dimensional systems. We have performed transport measurements on such decoupled graphene layers being jointly contacted and conducting in parallel to investigate the properties of charge carriers in both layers. Varying the charge carrier concentration and applying perpendicular magnetic field, the electric field effect, Shubnikov-de Haas oscillations and plateaus in the Hall resistance are observed. At the charge neutrality point, the resistance decreases by 15 percent with increasing temperature from 1.5 to 50 Kelvin. [ABSTRACT FROM AUTHOR]

The method of magnetotunneling spectroscopy has been used for experimental probing of heavy-hole impurity states in Si/Ge double-barrier heterostructures in magnetic field up to 18 Tesla. The impurities were located in a strained Ge quantum well with a thickness of four monolayers. We have observed a giant anisotropy of Zeeman splitting for these zero-dimensional systems. The splitting was measured as a function of angle between the external magnetic field and the quantum well plane. A complete suppression of the splitting takes place when the magnetic field is oriented parallel to the sample surface and quantum well plane, while in the perpendicular field the observed splitting is maximal. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

We demonstrate new results on electron redistribution on a single quantum dot caused by magnetic field. A quantum point contact is used to detect changes in the quantum dot charge. We are able to measure both the change of the quantum dot charge and also changes of the electron configuration at constant number of electrons on the quantum dot. These features are used to exploit the quantum dot in a high magnetic field where transport through the quantum dot displays the effects of Landau shells and spin blockade. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

We study the magnetoconductance of lateral quantum dots in high magnetic fields. We use spin blockade and Kondo effect to investigate the spin configuration and the spin filling mechanism and find a dependence on the electron number of the quantum dot. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

By single-electron tunneling spectroscopy we investigate the difference in spin splitting of single-electron resonances in a double-barrier structure subjected to a magnetic field perpendicular (Δ⊥) and parallel (Δ∥) to the plane of quantum well. The observed anisotropy of spin splitting is interpreted within a model of spin-orbit coupling in quantum dots. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The activation gap Δ of the fractional quantum Hall states at constant fillings v = 2/3 and 2/5 has been measured as a function of the perpendicular magnetic field B. A linear dependence of Δ on B is observed while approaching the spin polarization transition, yielding a direct measurement of the g-factor of Composite Fermions. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]