References of "New Journal of Physics"
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See detailMagnetic ghosts and monopoles
Vandewalle, Nicolas ULg; Dorbolo, Stéphane ULg

in New Journal of Physics (2014), 16

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See detailVortex ratchet induced by controlled edge roughness
Cerbu, D.; Gladilin, V.N.; Cuppens, J. et al

in New Journal of Physics (2013), 15

We demonstrate theoretically and experimentally the generation of rectified mean vortex displacement resulting from a controlled difference between the surface barriers at the opposite borders of a ... [more ▼]

We demonstrate theoretically and experimentally the generation of rectified mean vortex displacement resulting from a controlled difference between the surface barriers at the opposite borders of a superconducting strip. Our investigation focuses on Al superconducting strips where, in one of the two sample borders, a saw tooth-like array of micro-indentations has been imprinted. The origin of the vortex ratchet effect is based on the fact that (i) the onset of vortex motion is mainly governed by the entrance/nucleation of vortices and (ii) the current lines bunching produced by the indentations facilitates the entrance/nucleation of vortices. Only for one current direction the indentations are positioned at the side of vortex entry and the onset of the resistive regime is lowered compared to the opposite current direction. This investigation points to the relevance of ubiquitous border effects typically neglected when interpreting vortex ratchet measurements on samples with arrays of local asymmetric pinning sites. [less ▲]

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See detailInfluence of artificial pinning on vortex lattice instability in superconducting films
Silhanek, Alejandro ULg; Leo, A.; Grimaldi, G. et al

in New Journal of Physics (2012), 14

In superconducting films under an applied dc current, we analyze experimentally and theoretically the influence of engineered pinning on the vortex velocity at which the flux-flow dissipation undergoes an ... [more ▼]

In superconducting films under an applied dc current, we analyze experimentally and theoretically the influence of engineered pinning on the vortex velocity at which the flux-flow dissipation undergoes an abrupt transition from low to high resistance. We argue, based on a nonuniform distribution of vortex velocity in the sample, that in strongly disordered systems the mean critical vortex velocity for flux-flow instability (i) has a nonmonotonic dependence on magnetic field and (ii) decreases as the pinning strength is increased. These findings challenge the generally accepted microscopic model of Larkin and Ovchinnikov (1979 J. Low. Temp. Phys. 34 409) and all subsequent refinements of this model which ignore the presence of pinning centers. [less ▲]

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See detailQuantitative spatial magnetization distribution in iron oxide nanocubes and nanospheres by polarized small-angle neutron scattering
Disch, S.; Wetterskog, E.; Hermann, Raphaël ULg et al

in New Journal of Physics (2012), 14

By means of polarized small-angle neutron scattering, we have resolved the long-standing challenge of determining the magnetization distribution in magnetic nanoparticles in absolute units. The reduced ... [more ▼]

By means of polarized small-angle neutron scattering, we have resolved the long-standing challenge of determining the magnetization distribution in magnetic nanoparticles in absolute units. The reduced magnetization, localized in non-interacting nanoparticles, indicates strongly particle shape-dependent surface spin canting with a 0.3(1) and 0.5(1) nm thick surface shell of reduced magnetization found for similar to 9 nm nanospheres and similar to 8.5 nm nanocubes, respectively. Further, the reduced macroscopic magnetization in nanoparticles results not only from surface spin canting, but also from drastically reduced magnetization inside the uniformly magnetized core as compared to the bulk material. Our microscopic results explain the low macroscopic magnetization commonly found in nanoparticles. [less ▲]

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See detailThwarting the photon-number-splitting attack with entanglement-enhanced BB84 quantum key distribution
Richardson, Christopher ULg; Anisimov, Petr; Sabottke, Carl et al

in New Journal of Physics (2012), 14

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See detailTransport and interaction blockade of cold bosonic atoms in a triple-well potential
Schlagheck, Peter ULg; Malet, F.; Cremon, J. C. et al

in New Journal of Physics (2010), 12

We theoretically investigate the transport properties of cold bosonic atoms in a quasi-one-dimensional (1D) triple-well potential that consists of two large outer wells, which act as microscopic source ... [more ▼]

We theoretically investigate the transport properties of cold bosonic atoms in a quasi-one-dimensional (1D) triple-well potential that consists of two large outer wells, which act as microscopic source and drain reservoirs, and a small inner well, which represents a quantum-dot-like scattering region. Bias and gate 'voltages' introduce a time-dependent tilt of the triple-well configuration, and are used to shift the energetic level of the inner well with respect to the outer ones. By means of exact diagonalization considering a total number of six atoms in the triple-well potential, we find diamond-like structures for the occurrence of single-atom transport in the parameter space spanned by the bias and gate voltages. We discuss the analogy with Coulomb blockade in electronic quantum dots, and point out how one can infer the interaction energy in the central well from the distance between the diamonds. [less ▲]

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See detailInfluence of the rare-earth element on the effects of the structural and magnetic phase transitions in CeFeAsO, PrFeAsO and NdFeAsO
McGuire, Michael A; Hermann, Raphaël ULg; Sefat, Athena S et al

in New Journal of Physics (2009), 11

We present results of transport and magnetic properties and heat capacity measurements on polycrystalline CeFeAsO, PrFeAsO and NdFeAsO. These materials undergo structural phase transitions, spin density ... [more ▼]

We present results of transport and magnetic properties and heat capacity measurements on polycrystalline CeFeAsO, PrFeAsO and NdFeAsO. These materials undergo structural phase transitions, spin density wave-like magnetic ordering of small moments on iron and antiferromagnetic ordering of rare-earth moments. The temperature dependence of the electrical resistivity, Seebeck coefficient, thermal conductivity, Hall coefficient and magnetoresistance are reported. The magnetic behavior of the materials have been investigated using Mossbauer spectroscopy and magnetization measurements. Transport and magnetic properties are affected strongly by the structural and magnetic transitions, suggesting significant changes in the band structure and/or carrier mobilities occur, and phonon-phonon scattering is reduced upon transformation to the low-temperature structure. Results are compared with recent reports for LaFeAsO, and systematic variations in properties as the identity of Ln is changed are observed and discussed. As Ln progresses across the rare-earth series from La to Nd, an increase in the hole contributions to the Seebeck coefficient and increases in magnetoresistance and the Hall coefficient are observed in the low-temperature phase. Analysis of hyperfine fields at the iron nuclei determined from Mossbauer spectra indicates that the moment on Fe in the orthorhombic phase is nearly independent of the identity of Ln, in apparent contrast to reports of powder neutron diffraction refinements. [less ▲]

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See detailResonant and rolling droplet
Dorbolo, Stéphane ULg; Terwagne, Denis ULg; Vandewalle, Nicolas ULg et al

in New Journal of Physics (2008), 10

When an oil droplet is placed on a quiescent oil bath, it eventually collapses into the bath due to gravity. The resulting coalescence may be eliminated when the bath is vertically vibrated. The droplet ... [more ▼]

When an oil droplet is placed on a quiescent oil bath, it eventually collapses into the bath due to gravity. The resulting coalescence may be eliminated when the bath is vertically vibrated. The droplet bounces periodically on the bath, and the air layer between the droplet and the bath is replenished at each bounce. This sustained bouncing motion is achieved when the forcing acceleration is higher than a threshold value. When the droplet has a sufficiently low viscosity, it significantly deforms: spherical harmonic Y-1(m) modes are excited, resulting in resonant effects on the threshold acceleration curve. Indeed, a lower acceleration is needed when I modes with m = 0 are excited. Modes m not equal 0 are found to decrease the bouncing ability of the droplet. A break of degeneracy is observed for the m parameter. In particular, when the mode 1 = 2 and m = 1 is excited, the droplet rolls on the vibrated surface without touching it, leading to a new self-propulsion mode. [less ▲]

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See detailPump and probe ultrafast electron dynamics in LiH: a computational study
Nest, M.; Remacle, Françoise ULg; Levine, R. D.

in New Journal of Physics (2008), 10

A time-dependent multiconfiguration method with a large electronic basis set is used to compute the response of all the electrons of LiH to a few-cycle intense pump field followed by a probe pulse. The ... [more ▼]

A time-dependent multiconfiguration method with a large electronic basis set is used to compute the response of all the electrons of LiH to a few-cycle intense pump field followed by a probe pulse. The ultrashort pump pulse excites a coherent superposition of stationary electronic states and, by changing the pump parameters such as intensity, duration, polarization and phase of carrier frequency, one can steer the motion of the electrons. Particular attention is given to the control provided by the polarization and by the phase. For example, a change in polarization is used to select an electronic wave packet that is rotating in a plane perpendicular to the bond or rotation in a plane containing the bond. The electronic wave packet can be probed by a delayed second pulse. This delayed probe pulse is also included in the Hamiltonian with the result that the frequency dispersed probe spectrum can be computed and displayed as a two-dimensional plot. [less ▲]

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See detailTunable random packings
Lumay, Geoffroy ULg; Vandewalle, Nicolas ULg

in New Journal of Physics (2007), 9

We present an experimental protocol that allows one to tune the packing fraction eta of a random pile of ferromagnetic spheres from a value close to the lower limit of random loose packing eta(RLP ... [more ▼]

We present an experimental protocol that allows one to tune the packing fraction eta of a random pile of ferromagnetic spheres from a value close to the lower limit of random loose packing eta(RLP) similar or equal to 0.56 to the upper limit of random close packing eta(RCP) similar or equal to 0.64. This broad range of packing fraction values is obtained under normal gravity in air, by adjusting a magnetic cohesion between the grains during the formation of the pile. Attractive and repulsive magnetic interactions are found to affect stongly the internal structure and the stability of sphere packing. After the formation of the pile, the induced cohesion is decreased continuously along a linear decreasing ramp. The controlled collapse of the pile is found to generate various and reproducible values of the random packing fraction eta. [less ▲]

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See detailNon-linear optical measurements and crystalline characterization of CdTe nanoparticles produces by thes electropulse technique
Loicq, Jerôme ULg; Renotte, Yvon ULg; Delplancke, Jean-Luc

in New Journal of Physics (2004), 6(32),

We propose to extend the ‘electropulse’ technique to synthesize CdTe nanoparticles for optical components. To do so, we create nuclei of the expected material on a titanium electrode immersed in an ... [more ▼]

We propose to extend the ‘electropulse’ technique to synthesize CdTe nanoparticles for optical components. To do so, we create nuclei of the expected material on a titanium electrode immersed in an electrolytic solution by using an electrochemical pulse. The nanoparticles are expelled from the titanium horn surface by cavitation bubbles, which are produced in the solution by a high intensity ultrasound pulse generated by a piezoelectric crystal. Optical absorption spectra and third-order non-linear optical properties of a colloidal solution of CdTe particles produced by this technique are presented. The non-linear refractive index was characterized using the single-beam z-scan technique, and measurements were carried out at several incidence intensities. Non-linear indices of refraction between −1.2×10−7 and −2×10−8 cm2W−1 were measured. [less ▲]

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See detailFluid instabilities in the birth and death of antibubbles
Dorbolo, Stéphane ULg; Caps, Hervé ULg; Vandewalle, Nicolas ULg

in New Journal of Physics (2003), 5

Antibubbles have been produced and studied with the help of a high-speed camera. An antibubble is defined as a fluid object constituted by a thin air shell surrounding a liquid and surrounded by the same ... [more ▼]

Antibubbles have been produced and studied with the help of a high-speed camera. An antibubble is defined as a fluid object constituted by a thin air shell surrounding a liquid and surrounded by the same liquid. Images reveal some key physical processes and fluid instabilities which take place when an antibubble forms and dies. The collapsing speed of the air film has been measured. Culik's theory does not apply. A new mechanism has been introduced. [less ▲]

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See detailDust-acoustic modes in plasmas with dust distributions and charge fluctuations
Verheest, F.; Jacobs, G.; Cattaert, Tom ULg

in New Journal of Physics (2003), 5

Charge fluctuations in dusty plasmas are discussed starting from charge, mass, momentum and current equations for the combined dusty plasma. This allows a generic description of low-frequency waves in ... [more ▼]

Charge fluctuations in dusty plasmas are discussed starting from charge, mass, momentum and current equations for the combined dusty plasma. This allows a generic description of low-frequency waves in plasmas with dust distributions, and leads to the damping and other modifications of the dust-acoustic and related modes, like generalized dust-Coulomb modes. [less ▲]

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