[en] In a one-dimensional quantum mechanical model the phonon transmission between a solid and liquid He is calculated. It is shown how surface roughness changes the binding forces between the He atoms and the solid and therefore can lead to an increased transmission of low-energy phonons. In addition it turns out that the finite lifetimes of the He states also enhance the transmission probability

[en] The photoelectric emission from a pure or barium-coated single crystal tungsten tip submitted to a high electric field is studied under illumination by light of energy smaller than the work function of the substrate. The results are discussed according to the range of the electric field applied. It is found that the average values of the work function for barium coated tips as obtained by photofield emission are different from those obtained by field emission. The photofield emission and field emission patterns are compared. (Auth.)

[en] The MERIT experiment, to be run at CERN in 2007, is a proof-of-principle test for a target system that converts a 4-MW proton beam into a high-intensity muon beam for either a neutrino factory complex or a muon collider. The target system is based on a free mercury jet that intercepts an intense proton beam inside a 15-T solenoidal magnetic field. Here, we describe the design and initial performance of the 15-T, liquid-nitrogen-precooled, copper solenoid magnet

[en] An Atomic Force Microscope is used to alter one part of a single layer graphene sample locally. Transport experiments at low temperatures are then used to characterize the different parts independently with field effect and Hall measurements. It is shown, that the nanomachining leads to an effective doping in the altered area and therefore to a difference in the charge carrier density of Δn = 3.5 ⋅ 10¹⁵m⁻² between the unchanged and changed part. These two parts can be tuned with a global backgate to form a junction of different polarity, i.e. a p-n junction

[en] Quantum interference is observed in a graphene ring system via the Aharonov Bohm effect. As graphene is a gapless semiconductor, this geometry allows to study the unique situation of quantum interference between electrons and holes in addition to the unipolar quantum interference. The period and amplitude of the observed Aharonov-Bohm oscillations are independent of the sign of the applied gate voltage showing the equivalence between unipolar and dipolar interference

[en] We present transport measurements on a lateral triple quantum dot with a star-like geometry and one lead attached to each dot. The system is studied in a regime close to established quadruple points, where all three dots are in resonance. The specific sample structure allows us to apply two different bias voltages to the two source leads and thus to study the influence between the paths with serial double dots

[en] We present the full three dimensionality of an electrostatically calculated stability diagram for triple quantum dots. The stability diagram maps out the favored charge configuration of the system as a function of potential shifts due to gate voltages. For triple dots only a three-dimensional visualization allows for the complete identification of all its components. Those are most notably the so-called quadruple points where four electronic configurations are degenerate, and quantum cellular automata processes. The exact positions of these features within the stability diagram are now revealed. Furthermore, the influence on transport is studied by comparing the model with a two-path triple quantum dot made with local anodic oxidation. The two-path setup allows us to study the influence of the dots' arrangement.

[en] The influence of high magnetic fields on coherent transport is investigated. A monolayer graphene quantum ring is fabricated and the Aharonov-Bohm effect is observed. For increased magnitude of the magnetic field, higher harmonics appear. This phenomenon is attributed to an increase of the phase coherence length due to reduction of spin flip scattering.

[en] We present a lateral quantum dot device which has a tunable number of quantum dots. Depending on easily tunable gate voltages, one, two or three quantum dots are found. They are investigated in transport and charge detection

[en] Hysteresis in the field effect of bilayer graphene is observed at a low temperature. We attribute this effect to charge traps in the substrate. When the sweep rate of the back-gate voltage is increased to higher values, the hysteresis becomes more pronounced. By measuring the hysteresis in the field effect, the lifetime of the charge traps is estimated as 16.9 min. It is shown that the influence of charge traps on graphene is strongly affected by a magnetic field. Above 5 T the hysteresis remains constant.