371 research outputs found
Kondo resonance in a nanotube quantum dot coupled to a normal and a superconducting lead
We report on electrical transport measurements through a carbon nanotube
quantum dot coupled to a normal and a superconducting lead. The ratio of Kondo
temperature and superconducting gap is identified to govern the
transport properties of the system. In the case of the
conductance resonance splits into two resonances at . For the
opposite scenario the conductance resonance persists, however
the conductance is not enhanced compared to the normal state due to a relative
asymmetry of the lead-dot couplings. Within this limit the data is in agreement
with a simple model of a resonant SN-interface.Comment: 4 pages, 2 figures. submitted to the Proc. Rencontres de Moriond on
Quantum Information and Decoherence in Nanosystems 200
Permalloy-based carbon nanotube spin-valve
In this Letter we demonstrate that Permalloy (Py), a widely used Ni/Fe alloy,
forms contacts to carbon nanotubes (CNTs) that meet the requirements for the
injection and detection of spin-polarized currents in carbon-based spintronic
devices. We establish the material quality and magnetization properties of Py
strips in the shape of suitable electrical contacts and find a sharp
magnetization switching tunable by geometry in the anisotropic
magnetoresistance (AMR) of a single strip at cryogenic temperatures. In
addition, we show that Py contacts couple strongly to CNTs, comparable to Pd
contacts, thereby forming CNT quantum dots at low temperatures. These results
form the basis for a Py-based CNT spin-valve exhibiting very sharp resistance
switchings in the tunneling magnetoresistance, which directly correspond to the
magnetization reversals in the individual contacts observed in AMR experiments.Comment: 3 page
Amplitude of Aharonov-Bohm oscillations in mesoscopic metallic rings as a function of the DC bias voltage
We report measurements of the amplitude of the Aharonov-Bohm oscillations in a mesoscopic diffusive gold ring as a function of the DC bias voltage VDC. The amplitude of the h/e oscillations increases with VDC once the Thouless energy Ec and thermal energy are exceeded, and decreases at higher values of VDC. The increase of the amplitude is interpreted in terms of a superposition of the statistically independent contributions of eVDC/Ec energy intervals, whereas its decrease at high VDC could be attributed to enhanced inelastic scattering processes
Formation of Actin Networks in Microfluidic Concentration Gradients
The physical properties of cytoskeletal networks are contributors in a number of mechanical responses of cells, including cellular deformation and locomotion, and are crucial for the proper action of living cells. Local chemical gradients modulate cytoskeletal functionality including the interactions of the cytoskeleton with other cellular components. Actin is a major constituent of the cytoskeleton. Introducing a microfluidic-based platform, we explored the impact of concentration gradients on the formation and structural properties of actin networks. Microfluidic-controlled flow-free and steady-state experimental conditions allow for the generation of chemical gradients of different profiles, such as linear or step-like. We discovered specific features of actin networks emerging in defined gradients. In particular, we analyzed the effects of spatial conditions on network properties, bending rigidities of network links, and the network elasticity
Amplitude of Aharonov-Bohm oscillations in mesoscopic metallic rings as a function of the DC bias voltage
We report measurements of the amplitude of the Aharonov-Bohm oscillations in a mesoscopic diffusive gold ring as a function of the DC bias voltage VDC. The amplitude of the h/e oscillations increases with VDC once the Thouless energy Ec and thermal energy are exceeded, and decreases at higher values of VDC. The increase of the amplitude is interpreted in terms of a superposition of the statistically independent contributions of eVDC/Ec energy intervals, whereas its decrease at high VDC could be attributed to enhanced inelastic scattering processes
Implementing Silicon Nanoribbon Field-Effect Transistors as Arrays for Multiple Ion Detection
Ionic gradients play a crucial role in the physiology of the human body, ranging from metabolism in cells to muscle contractions or brain activities. To monitor these ions, inexpensive, label-free chemical sensing devices are needed. Field-effect transistors (FETs) based on silicon (Si) nanowires or nanoribbons (NRs) have a great potential as future biochemical sensors as they allow for the integration in microscopic devices at low production costs. Integrating NRs in dense arrays on a single chip expands the field of applications to implantable electrodes or multifunctional chemical sensing platforms. Ideally, such a platform is capable of detecting numerous species in a complex analyte. Here, we demonstrate the basis for simultaneous sodium and fluoride ion detection with a single sensor chip consisting of arrays of gold-coated SiNR FETs. A microfluidic system with individual channels allows modifying the NR surfaces with self-assembled monolayers of two types of ion receptors sensitive to sodium and fluoride ions. The functionalization procedure results in a differential setup having active fluoride-and sodium-sensitive NRs together with bare gold control NRs on the same chip. Comparing functionalized NRs with control NRs allows the compensation of non-specific contributions from changes in the background electrolyte concentration and reveals the response to the targeted species
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