Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Full Text
Peer Reviewed
See detailExchange-stiffness constant of a Nd-Fe-B based nanocomposite determined by magnetic neutron scattering
Bick, Jens-Peter UL; Suzuki, Kiyonori; Gilbert, Elliot et al

in Applied Physics Letters (2013), 103

Detailed reference viewed: 109 (20 UL)
Full Text
Peer Reviewed
See detailExchangeable Hoeffding decompositions over finite sets: a characterization and counterexamples
El-Dakkak, Omar; Peccati, Giovanni UL; Prünster, Igor

in Journal of Multivariate Analysis (2014), 131

Detailed reference viewed: 21 (1 UL)
Peer Reviewed
See detailExchangeable pairs on Wiener chaos
Nourdin, Ivan UL; Zheng, Guangqu UL

in High-Dimensional Probability VIII Proceedings (2017)

Detailed reference viewed: 76 (5 UL)
Full Text
Peer Reviewed
See detailExcitation energy and pair correlation function of trions near an LiF surface
Solleder, Beate; Wirtz, Ludger UL; Burgdörfer, Joachim

in Physical Review B (2008), 78(15),

We investigate the excitation spectrum of a singly charged LiF surface using an embedded cluster approach. The spectrum is determined by multiconfiguration self-consistent field calculations. We find ... [more ▼]

We investigate the excitation spectrum of a singly charged LiF surface using an embedded cluster approach. The spectrum is determined by multiconfiguration self-consistent field calculations. We find stable trionic states, i.e., quasimolecular states of a three-quasiparticle complex consisting of two holes and one electron interacting through the Coulomb potential. The excitation energy of the lowest trionic state is approximately 12.1 eV. The mean hole-hole spacing is about 7.6 a.u. (or 4 A). Our results confirm the interpretation of experiments [P. Roncin , Phys. Rev. Lett. 89, 043201 (2002)] where trion excitation was suggested as effective energy-loss channel during the neutralization of Ne(+) ions at an LiF surface. [less ▲]

Detailed reference viewed: 82 (0 UL)
Full Text
Peer Reviewed
See detailExcitation of Ni nanorod colloids in oscillating magnetic fields: a new approach for nanosensing investigated by TISANE
Bender, Philipp; Günther, Annegret UL; Honecker, Dirk UL et al

in Nanoscale (2015), 7

The response of a colloidal dispersion of Ni nanorods to an oscillating magnetic field was characterized by optical transmission measurements as well as small-angle neutron scattering (SANS) experiments ... [more ▼]

The response of a colloidal dispersion of Ni nanorods to an oscillating magnetic field was characterized by optical transmission measurements as well as small-angle neutron scattering (SANS) experiments using the TISANE (Time-dependent SANS experiments) technique. Exposed to a static magnetic field, the scattering intensity of the rod ensemble could be well described by the cylinder form factor using the geometrical particle parameters (length, diameter, orientation distribution) determined by transmission electronmicroscopy and magnetometry. An oscillation of the field vector resulted in a reorientation of the nanorods and a time-dependency of the scattering intensity due to the shape anisotropy of the rods. Analysis of the SANS data revealed that in the range of low frequencies the orientation distribution of the rods is comparable to the static case. With increasing frequency, the rod oscillation was gradually damped due to an increase of the viscous drag. It could be shown that despite of the increased friction in the high frequency range no observable change of the orientation distribution of the ensemble with respect to its symmetry axis occurs. [less ▲]

Detailed reference viewed: 86 (7 UL)
Full Text
Peer Reviewed
See detailExciton-Phonon Coupling in the Ultraviolet Absorption and Emission Spectra of Bulk Hexagonal Boron Nitride
Paleari, Fulvio UL; Miranda, Henrique P. C.; Molina-Sanchez, Alejandro et al

in PHYSICAL REVIEW LETTERS (2019), 122(18), 187401-6

We present an ab initio method to calculate phonon-assisted absorption and emission spectra in the presence of strong excitonic effects. We apply the method to bulk hexagonal BN, which has an indirect ... [more ▼]

We present an ab initio method to calculate phonon-assisted absorption and emission spectra in the presence of strong excitonic effects. We apply the method to bulk hexagonal BN, which has an indirect band gap and is known for its strong luminescence in the UV range. We first analyze the excitons at the wave vector (q) over bar of the indirect gap. The coupling of these excitons with the various phonon modes at (q) over bar is expressed in terms of a product of the mean square displacement of the atoms and the second derivative of the optical response function with respect to atomic displacement along the phonon eigenvectors. The derivatives are calculated numerically with a finite difference scheme in a supercell commensurate with (q) over bar. We use detailed balance arguments to obtain the intensity ratio between emission and absorption processes. Our results explain recent luminescence experiments and reveal the exciton-phonon coupling channels responsible for the emission lines. [less ▲]

Detailed reference viewed: 83 (6 UL)
Full Text
Peer Reviewed
See detailExcitons in a mirror: Formation of “optical bilayers” using MoS2 monolayers on gold substrates
Mertens, Jan; Shi, Yumeng; Molina-Sanchez, Alejandro UL et al

in Applied Physics Letters (2014), 104

We report coupling of excitons in monolayers of molybdenum disulphide to their mirror image in an underlying gold substrate. Excitons at the direct band gap are little affected by the substrate whereas ... [more ▼]

We report coupling of excitons in monolayers of molybdenum disulphide to their mirror image in an underlying gold substrate. Excitons at the direct band gap are little affected by the substrate whereas strongly bound C-excitons associated with a van-Hove singularity change drastically. On quartz substrates only one C-exciton is visible (in the blue) but on gold substrates a strong red-shifted extra resonance in the green is seen. Exciton coupling to its image leads to formation of a “mirror biexciton” with enhanced binding energy. Estimates of this energy shift in an emitter-gold system match experiments well. The absorption spectrum of MoS2 on gold thus resembles a bilayer of MoS2 which has been created by optical coupling. Additional top-mirrors produce an “optical bulk.” [less ▲]

Detailed reference viewed: 260 (11 UL)
Full Text
Peer Reviewed
See detailExcitons in boron nitride nanotubes: Dimensionality effects
Wirtz, Ludger UL; Marini, A.; Rubio, A.

in Physical Review Letters (2006), 96(12), 126104

We show that the optical absorption spectra of boron nitride (BN) nanotubes are dominated by strongly bound excitons. Our first-principles calculations indicate that the binding energy for the first and ... [more ▼]

We show that the optical absorption spectra of boron nitride (BN) nanotubes are dominated by strongly bound excitons. Our first-principles calculations indicate that the binding energy for the first and dominant excitonic peak depends sensitively on the dimensionality of the system, varying from 0.7 eV in bulk hexagonal BN via 2.1 eV in the single sheet of BN to more than 3 eV in the hypothetical (2,2) tube. The strongly localized nature of this exciton dictates the fast convergence of its binding energy with increasing tube diameter towards the sheet value. The absolute position of the first excitonic peak is almost independent of the tube radius and system dimensionality. This provides an explanation for the observed "optical gap" constancy for different tubes and bulk hexagonal BN. [less ▲]

Detailed reference viewed: 78 (1 UL)
Full Text
Peer Reviewed
See detailExcitons in boron nitride single layer
Galvani, Thomas; Paleari, Fulvio UL; Pereira Coutada Miranda, Henrique UL et al

in Physical Review. B : Condensed Matter (2016), 94(125303),

Boron nitride single layer belongs to the family of two-dimensional materials whose optical properties are currently receiving considerable attention. Strong excitonic effects have already been observed ... [more ▼]

Boron nitride single layer belongs to the family of two-dimensional materials whose optical properties are currently receiving considerable attention. Strong excitonic effects have already been observed in the bulk and still stronger effects are predicted for single layers. We present here a detailed study of these properties by combining ab initio calculations and a tight-binding Wannier analysis in both real and reciprocal space. Due to the simplicity of the band structure with single valence (π) and conduction (π∗) bands the tight-binding analysis becomes quasiquantitative with only two adjustable parameters and provides tools for a detailed analysis of the exciton properties. Strong deviations from the usual hydrogenic model are evidenced. The ground-state exciton is not a genuine Frenkel exciton, but a very localized tightly bound one. The other ones are similar to those found in transition-metal dichalcogenides and, although more localized, can be described within a Wannier-Mott scheme. [less ▲]

Detailed reference viewed: 260 (22 UL)
Full Text
Peer Reviewed
See detailExcitons in few-layer hexagonal boron nitride: Davydov splitting and surface localization
Paleari, Fulvio UL; Galvani, Thomas UL; Amara, Hakim et al

in 2D MATERIALS (2018), 5(4), 045017

Hexagonal boron nitride (hBN) has been attracting great attention because of its strong excitonic effects. Taking into account few-layer systems, we investigate theoretically the effects of the number of ... [more ▼]

Hexagonal boron nitride (hBN) has been attracting great attention because of its strong excitonic effects. Taking into account few-layer systems, we investigate theoretically the effects of the number of layers on quasiparticle energies, absorption spectra, and excitonic states, placing particular focus on the Davydov splitting of the lowest bound excitons. We describe how the inter-layer interaction as well as the variation in electronic screening as a function of layer number N affects the electronic and optical properties. Using both ab initio calculations and a tight-binding model for an effective Hamiltonian describing the excitons, we characterize in detail the symmetry of the excitonic wavefunctions and the selection rules for their coupling to incoming light. We show that for N > 2, one can distinguish between surface excitons that are mostly localized on the outer layers and inner excitons, leading to an asymmetry in the energy separation between split excitonic states. In particular, the bound surface excitons lie lower in energy than their inner counterparts. Additionally, this enables us to show how the layer thickness affects the shape of the absorption spectrum. [less ▲]

Detailed reference viewed: 104 (8 UL)
Full Text
Peer Reviewed
See detailExcludability and Contribution: A Laboratory Study in Team Production
Neugebauer, Tibor UL; Fatás; Croson

E-print/Working paper (2012)

Detailed reference viewed: 70 (1 UL)
Full Text
Peer Reviewed
See detailExcludability: A laboratory study on forced ranking in team production
Neugebauer, Tibor UL; Croson, Rachel; Fatas, Enrique et al

in Journal of Economic Behavior & Organization (2015), 114

Detailed reference viewed: 58 (3 UL)
Peer Reviewed
See detailExcluding Children from Refugee Status: Child Soldiers and Article 1F of the Refugee Convention’
Happold, Matthew UL

in American University International Law Review (2002), 17

Detailed reference viewed: 119 (1 UL)
Peer Reviewed
See detailExclusion of the C/D box snoRNA gene cluster HBII-52 from a major role in Prader–Willi syndrome
Runte, Maren UL; Varon, R; Horn, D et al

in Human Genetics (2005), 116(3), 228-230

Detailed reference viewed: 59 (0 UL)
Peer Reviewed
See detail«Excursie naar Parijs op 30 november 2006 van Romaans: Frans»
Roelens, Nathalie UL

in Lettergrepen (2007)

Detailed reference viewed: 20 (3 UL)
Full Text
See detailExecuting Trades in Style: Retail Investors vs. Institutions
Wolff, Christian UL; Ekkayokkaya, Manapol

E-print/Working paper (2018)

Detailed reference viewed: 5 (0 UL)
See detailExécution au Luxembourg d'une sentence arbitrale annulée dans son Etat d'origine : note sous CA Luxembourg, 25 juin 2015
Cuniberti, Gilles UL

in Pasicrisie Luxembourgeoise : Recueil Trimestriel de la Jurisprudence Luxembourgeoise (2015)

Exécution au Luxembourg d’une sentence arbitrale soumise à un recours en annulation au pays du siège.

Detailed reference viewed: 40 (1 UL)
Peer Reviewed
See detailExécution des contrats et exécution des décisions de justice
Ancel, Pascal UL

in L'exécution (1999)

Detailed reference viewed: 50 (0 UL)