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Leiden, Netherlands

Vercruyssen N.,Technical University of Delft | Verhagen T.G.A.,Technical University of Delft | Verhagen T.G.A.,Leiden University | Flokstra M.G.,Leiden Institute of Physics | And 2 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We study the nonlinear response of current transport in a superconducting diffusive nanowire between normal reservoirs. We demonstrate theoretically and experimentally the existence of two different superconducting states appearing when the wire is driven out of equilibrium by an applied bias, called the global and bimodal superconducting states. The different states are identified by using two-probe measurements of the wire, and measurements of the local density of states with tunneling probes. The analysis is performed within the framework of the quasiclassical kinetic equations for diffusive superconductors. © 2012 American Physical Society. Source


Tromp R.M.,IBM | Tromp R.M.,Leiden Institute of Physics
Ultramicroscopy | Year: 2015

In this paper I briefly review the use of electrostatic electron mirrors to correct the aberrations of the cathode lens objective lens in low energy electron microscope (LEEM) and photo electron emission microscope (PEEM) instruments. These catadioptric systems, combining electrostatic lens elements with a reflecting mirror, offer a compact solution, allowing simultaneous and independent correction of both spherical and chromatic aberrations. A comparison with catadioptric systems in light optics informs our understanding of the working principles behind aberration correction with electron mirrors, and may point the way to further improvements in the latter. With additional developments in detector technology, 1. nm spatial resolution in LEEM appears to be within reach. © 2014 Elsevier B.V. Source


Faez S.,Max Planck Institute for the Science of Light | Faez S.,Leiden Institute of Physics | Turschmann P.,Max Planck Institute for the Science of Light | Haakh H.R.,Max Planck Institute for the Science of Light | And 4 more authors.
Physical Review Letters | Year: 2014

Many of the currently pursued experiments in quantum optics would greatly benefit from a strong interaction between light and matter. Here, we present a simple new scheme for the efficient coupling of single molecules and photons. A glass capillary with a diameter of 600 nm filled with an organic crystal tightly guides the excitation light and provides a maximum spontaneous emission coupling factor (β) of 18% for the dye molecules doped in the organic crystal. A combination of extinction, fluorescence excitation, and resonance fluorescence spectroscopy with microscopy provides high-resolution spatiospectral access to a very large number of single molecules in a linear geometry. We discuss strategies for exploring a range of quantum-optical phenomena, including polaritonic interactions in a mesoscopic ensemble of molecules mediated by a single mode of propagating photons. © 2014 American Physical Society. Source


Beutel O.,University of Osnabruck | Nikolaus J.,Humboldt University of Berlin | Birkholz O.,University of Osnabruck | You C.,University of Osnabruck | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2014

Lipid analogues carrying three nitrilotriacetic acid (tris-NTA) head groups were developed for the selective targeting of His-tagged proteins into liquid ordered (lo) or liquid disordered (ld) lipid phases. Strong partitioning into the lo phase of His-tagged proteins bound to tris-NTA conjugated to saturated alkyl chains (tris-NTA DODA) was achieved, while tris-NTA conjugated to an unsaturated alkyl chain (tris- NTA SOA) predominantly resided in the ld phase. Interestingly, His-tag-mediated lipid crosslinking turned out to be required for efficient targeting into the lo phase by tris-NTA DODA. Robust partitioning into lo phases was confirmed by using viral lipid mixtures and giant plasma membrane vesicles. Moreover, efficient protein targeting into lo and ld domains within the plasma membrane of living cells was demonstrated by singlemolecule tracking, thus establishing a highly generic approach for exploring lipid microdomains in situ. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Tromp R.M.,IBM | Tromp R.M.,Leiden Institute of Physics
Ultramicroscopy | Year: 2015

Chromatic aberration correction in light optics began with the invention of a two-color-corrected achromatic crown/flint lens doublet by Chester Moore Hall in 1730. Such color correction is necessary because any single glass shows dispersion (i.e. its index of refraction changes with wavelength), which can be counteracted by combining different glasses with different dispersions. In cathode lens microscopes (such as Photo Electron Emission Microscopy - PEEM) we encounter a similar situation, where the chromatic aberration coefficient of the cathode lens shows strong dispersion, i.e. depends (non-linearly) on the energy with which the electrons leave the sample. Here I show how a cathode lens in combination with an electron mirror can be configured as an adjustable electron achromat. The lens/mirror combination can be corrected at two electron energies by balancing the settings of the electron mirror against the settings of the cathode lens. The achromat can be adjusted to deliver optimum performance, depending on the requirements of a specific experiment. Going beyond the achromat, an apochromat would improve resolution and transmission by a very significant margin. I discuss the requirements and outlook for such a system, which for now remains a wish waiting for fulfilment. © 2015 Elsevier B.V. Source

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