- Electron-spin dephasing via hyperfine interaction in a quantum dot: An equation-of-motion calculation of electron-spin correlation functions
Author(s): Changxue Deng and Xuedong Hu
In this paper we develop an equation-of-motion (EOM) approach to study the non-Markovian single-electron-spin dynamics due to its inhomogeneous hyperfine coupling to the surrounding nuclei in a quantum dot. In particular, we identify an electron-spin correlation function that fully represents the el...
[Phys. Rev. B 78, 245301] Published Tue Dec 02, 2008
- Combining M - and L -edge resonant inelastic x-ray scattering for studies of 3d transition metal compounds
Author(s): S. G. Chiuzbăian, T. Schmitt, M. Matsubara, A. Kotani, G. Ghiringhelli, C. Dallera, A. Tagliaferri, L. Braicovich, V. Scagnoli, N. B. Brookes, U. Staub, and L. Patthey
Resonant inelastic x-ray scattering (RIXS) measurements performed jointly across the M_{2,3} and L_{3} absorption thresholds are used to study CoO local electronic structure and are supported by model calculations. The high-resolution experimental data provide a precise set of parameters to describe...
[Phys. Rev. B 78, 245102] Published Tue Dec 02, 2008
- Bond excitations in the pseudogap phase of the Hubbard model
Author(s): Alexandru Macridin and M. Jarrell
Using the dynamical cluster approximation, we calculate the correlation functions associated with the nearest-neighbor bond operator which measure the z component of the spin exchange in the two-dimensional Hubbard model with U equal to the bandwidth. We find that in the pseudogap region, the local ...
[Phys. Rev. B 78, 241101] Published Tue Dec 02, 2008
- Thermodynamic modeling of pyroelectric and piezoelectric properties of cellular polymers
Author(s): B. J. Mokross, M. Kollosche, T. Ruscher, G. Kofod, and R. Gerhard
A thermodynamic approach is presented to model devices manufactured with cellular polymers. They are heterogeneous nonpolar space-charge electrets that exhibit much higher piezoelectricity than the well-known ferroelectric polymers. Their pyroelectric and piezoelectric properties are characterized b...
[Phys. Rev. B 78, 235407] Published Tue Dec 02, 2008
- Coupling of orthogonal diffusion modes in two-dimensional nonhomogeneous systems
Author(s): Filip Krzyżewski and Magdalena A. Załuska-Kotur
Collective diffusion coefficient in a two-dimensional lattice gas on a nonhomogeneous substrate is investigated using variational approach. In our model particles reside and jump randomly between adsorption sites modeled as potential wells with different depths. Site blocking is the only allowed par...
[Phys. Rev. B 78, 235406] Published Tue Dec 02, 2008
- Chirality-dependent frequency shift of radial breathing mode in metallic carbon nanotubes
Author(s): Ken-ichi Sasaki, Riichiro Saito, Gene Dresselhaus, Mildred S. Dresselhaus, Hootan Farhat, and Jing Kong
A phonon frequency shift of the radial breathing mode for metallic single wall carbon nanotubes is predicted as a function of Fermi energy. Armchair nanotubes do not show any frequency shift while zigzag nanotubes exhibit phonon softening, but this softening is not associated with the broadening. Th...
[Phys. Rev. B 78, 235405] Published Tue Dec 02, 2008
- Localization of electronic states in finite ladder models: Participation ratio and localization length as measures of the wave-function extension
Author(s): H. Carrillo-Nuñez and Peter A. Schulz
In this work we discuss and compare different definitions for localization of electronic states in low-dimensional systems. We choose a heuristic model for DNA-like molecules as a system prototype in order to establish ranges of equivalence for the localization length obtained from both the conducta...
[Phys. Rev. B 78, 235404] Published Tue Dec 02, 2008
- Electronic structure investigation of the cubic inverse perovskite Sc_{3} AlN
Author(s): Martin Magnuson, Maurizio Mattesini, Carina Höglund, Igor A. Abrikosov, Jens Birch, and Lars Hultman
The electronic structure and chemical bonding of the recently discovered inverse perovskite Sc_{3} AlN , in comparison to those of ScN and Sc metal, have been investigated by bulk-sensitive soft-x-ray emission spectroscopy. The measured Sc L , N K , Al L_{1} , and Al L_{2,3} emission spectra...
[Phys. Rev. B 78, 235102] Published Tue Dec 02, 2008
- Theory of backward second-harmonic localization in nonlinear left-handed media
Author(s): Emmanuel Centeno and Cristian Ciracì
Recent research on photonic crystals possessing a quadratic nonlinear response has revealed a second-harmonic light localization phenomenon that originates from an all-angle phase matching between counterpropagating Bloch modes at the fundamental and double frequencies [E. Centeno , Phys. Rev. Lett....
[Phys. Rev. B 78, 235101] Published Tue Dec 02, 2008
- First-principles calculations of dielectric and optical properties of MgB_{2}
Author(s): A. Balassis, E. V. Chulkov, P. M. Echenique, and V. M. Silkin
We report on the results of calculation of low-energy dielectric response and optical properties of MgB_{2} . The calculations have been performed with full inclusion of the ab initio electron band structure making use of random-phase and time-dependent local-density approximations. The role of loca...
[Phys. Rev. B 78, 224502] Published Tue Dec 02, 2008
- Lattice properties of PbX (X=S,Se,Te) : Experimental studies and ab initio calculations including spin-orbit effects
Author(s): A. H. Romero, M. Cardona, R. K. Kremer, R. Lauck, G. Siegle, J. Serrano, and X. C. Gonze
During the past five years the low-temperature heat capacity of simple semiconductors and insulators has received renewed attention. Of particular interest is its dependence on isotopic masses and the effect of spin-orbit coupling in ab initio calculations. Here we concentrate on the lead chalcogeni...
[Phys. Rev. B 78, 224302] Published Tue Dec 02, 2008
- Depinning in a two-layer model of plastic flow
Author(s): Pierre Le Doussal, M. Cristina Marchetti, and Kay Jörg Wiese
We study a model of two layers, each consisting of a d -dimensional elastic object driven over a random substrate, and mutually interacting through a viscous coupling. For this model, the mean-field theory (i.e., a fully connected model) predicts a transition from elastic depinning to hysteretic pla...
[Phys. Rev. B 78, 224201] Published Tue Dec 02, 2008
- High-energy spin excitations in BaFe_{2} As_{2} observed by inelastic neutron scattering
Author(s): R. A. Ewings, T. G. Perring, R. I. Bewley, T. Guidi, M. J. Pitcher, D. R. Parker, S. J. Clarke, and A. T. Boothroyd
We report neutron-scattering measurements of cooperative spin excitations in antiferromagnetically ordered BaFe_{2} As_{2} , the parent phase of an iron pnictide superconductor. The data extend up to ∼100 meV and show that the spin excitation spectrum is sharp and highly dispersive. By fitting t...
[Phys. Rev. B 78, 220501] Published Tue Dec 02, 2008
- Almeida-Thouless transition below six dimensions
Author(s): T. Temesvári
The existence of an Almeida-Thouless (AT) instability surface below the upper critical six dimensions is demonstrated in the generic replica symmetric field theory. Renormalization flows from around the zero-field fixed point are investigated. By introducing the temperature and magnetic-field depend...
[Phys. Rev. B 78, 220401] Published Tue Dec 02, 2008
- Muon-spin-relaxation studies of magnetic order and superfluid density in antiferromagnetic NdFeAsO, BaFe_{2} As_{2} , and superconducting Ba_{1−x} K_{x} Fe_{2} As_{2}
Author(s): A. A. Aczel, E. Baggio-Saitovitch, S. L. Budko, P. C. Canfield, J. P. Carlo, G. F. Chen, Pengcheng Dai, T. Goko, W. Z. Hu, G. M. Luke, J. L. Luo, N. Ni, D. R. Sanchez-Candela, F. F. Tafti, N. L. Wang, T. J. Williams, W. Yu, and Y. J. Uemura
Zero-field (ZF) muon-spin-relaxation (μSR) measurements have revealed static commensurate magnetic order of Fe moments in NdFeAsO below T_{N} ∼135 K , with the ordered moment size nearly equal to that in LaFeAsO, and confirmed similar behavior in BaFe_{2} As_{2} . In single crystals of supercon...
[Phys. Rev. B 78, 214503] Published Tue Dec 02, 2008
- Long-ranged dynamic magnetic interaction through low-dimensional systems
Author(s): A. T. Costa, R. B. Muniz, M. S. Ferreira, and D. L. Mills
Magnetic units attached to low-dimensional metallic nanowires are known to interact via the conduction electrons of the wire leading to preferential alignment directions of the respective magnetic moments. In addition to this so-called static interaction, here we show that a very long-ranged interac...
[Phys. Rev. B 78, 214403] Published Tue Dec 02, 2008
- Characteristic muon precession and relaxation signals in FeAs and FeAs_{2} : Possible impurity phases in pnictide superconductors
Author(s): P. J. Baker, H. J. Lewtas, S. J. Blundell, T. Lancaster, F. L. Pratt, D. R. Parker, M. J. Pitcher, and S. J. Clarke
We report muon-spin relaxation measurements of highly homogeneous samples of FeAs and FeAs_{2} , both previously found as impurity phases in some samples of recently synthesized pnictide superconductors. We observe well-defined muon precession in the FeAs sample with two precession frequencies of 38...
[Phys. Rev. B 78, 212501] Published Tue Dec 02, 2008
- Giant planar Hall effect in epitaxial Fe_{3} O_{4} thin films and its temperature dependence
Author(s): A. Fernández-Pacheco, J. M. De Teresa, J. Orna, L. Morellon, P. A. Algarabel, J. A. Pardo, M. R. Ibarra, C. Magen, and E. Snoeck
We have investigated the giant planar Hall effect (ρ_{xy} ) in epitaxial thin films of Fe_{3} O_{4} grown on MgO (001) substrates with thickness ranging from 5 to 150 nm. A record value at room temperature of |ρ_{xy} |≈60 μΩ cm was obtained for the 5-nm-thick film. Below room temperature, ...
[Phys. Rev. B 78, 212402] Published Tue Dec 02, 2008
- Homogeneous large-area graphene layer growth on 6H -SiC(0001)
Author(s): C. Virojanadara, M. Syväjarvi, R. Yakimova, L. I. Johansson, A. A. Zakharov, and T. Balasubramanian
Homogeneous large-area graphene monolayers were successfully prepared ex situ on 6H -SiC(0001). The samples have been studied systematically and the results are compared with those from a sample cut from the same wafer and prepared by in situ heating. The formation of smaller graphene flakes was fou...
[Phys. Rev. B 78, 245403] Published Mon Dec 01, 2008
- Superlattice structures of graphene-based armchair nanoribbons
Author(s): H. Sevinçli, M. Topsakal, and S. Ciraci
Based on first-principles calculations we predict that periodically repeated junctions of armchair graphene nanoribbons of different widths form multiple quantum well structures. In these superlattice heterostructures the width as well as the energy-band gap is modulated in real space and specific s...
[Phys. Rev. B 78, 245402] Published Mon Dec 01, 2008
- Beam transit effects in single molecule coherent diffraction
Author(s): J. M. Gibson and M. M. J. Treacy
We explore how phase and amplitude gradients, which are almost inevitable in a coherent illumination probe, affect the atomic reconstruction of an isolated molecule based on diffraction intensities. By modeling the probe as a defocused Gaussian source, we show that structural distortion can be intro...
[Phys. Rev. B 78, 245401] Published Mon Dec 01, 2008
- Electrochemical doping during light emission in polymer light-emitting electrochemical cells
Author(s): Nathaniel D. Robinson, Junfeng Fang, Piotr Matyba, and Ludvig Edman
Polymer light-emitting electrochemical cells (LECs), the electrochemical analog of light-emitting diodes, are relatively simple to manufacture yet difficult to understand. The combination of ionic and electronic charge carriers make for a richly complex electrochemical device. This paper addresses t...
[Phys. Rev. B 78, 245202] Published Mon Dec 01, 2008
- Distance dependence of excitation energy transfer between spacer-separated conjugated polymer films
Author(s): Paul E. Shaw, Arvydas Ruseckas, and Ifor D. W. Samuel
We report a systematic study of the scaling with distance of electronic energy transfer between thin films of conjugated polymers separated by a silica spacer. The energy-transfer kinetics were obtained directly from time-resolved photoluminescence measurements and show a 1/z^{3} distance dependence...
[Phys. Rev. B 78, 245201] Published Mon Dec 01, 2008
- Coupling between the 4f core binding energy and the 5f valence band occupation of elemental Pu and Pu-based compounds
Author(s): Torbjörn Björkman, Olle Eriksson, and Per Andersson
We demonstrate that there is a close coupling between 4f core binding energy and 5f valence band occupation for Pu-based materials. This enables accurate determination of the valence occupation of this class of materials by simply measuring the 4f core binding energy. Our study demonstrates that all...
[Phys. Rev. B 78, 245101] Published Mon Dec 01, 2008
- Detecting entangled states in graphene via crossed Andreev reflection
Author(s): Colin Benjamin and Jiannis K. Pachos
Shot-noise cross correlations across single layer graphene structures are calculated with insulators separating a superconducting region. A different feature of specular crossed Andreev reflection comes into play due to the unique band structure of graphene. This gives rise to a rich structure in th...
[Phys. Rev. B 78, 235403] Published Mon Dec 01, 2008
- Optically polarized ^{129} Xe NMR investigation of carbon nanotubes
Author(s): Catherine F. M. Clewett, Steven W. Morgan, Brian Saam, and Tanja Pietraß
We demonstrate the utility of optically polarized ^{129} Xe NMR in a convection cell for measuring the surface properties of materials. In particular, we show adsorption of xenon gas on oxidatively purified single- and multiwalled carbon nanotubes. The interaction between xenon and multiwalled nanot...
[Phys. Rev. B 78, 235402] Published Mon Dec 01, 2008
- Facet evolution on supported nanostructures: Effect of finite height
Author(s): Pak-Wing Fok, Rodolfo R. Rosales, and Dionisios Margetis
The surface of a nanostructure relaxing on a substrate consists of a finite number of interacting steps and often involves the expansion of facets. Prior theoretical studies of facet evolution have focused on models with an infinite number of steps, which neglect edge effects caused by the presence ...
[Phys. Rev. B 78, 235401] Published Mon Dec 01, 2008
- Comparison of atomistic and continuum theoretical approaches to determine electronic properties of GaN/AlN quantum dots
Author(s): Oliver Marquardt, Daniel Mourad, Stefan Schulz, Tilmann Hickel, Gerd Czycholl, and Jörg Neugebauer
In this work we present a comparison of multiband k⋅p models, the effective-bond-orbital approach, and an empirical tight-binding model to calculate the electronic structure for the example of a truncated pyramidal GaN/AlN self-assembled quantum dot with a zinc-blende structure. For the system und...
[Phys. Rev. B 78, 235302] Published Mon Dec 01, 2008
- Growth kinetics and crystal structure of semiconductor nanowires
Author(s): V. G. Dubrovskii, N. V. Sibirev, J. C. Harmand, and F. Glas
Theoretical model for the growth of semiconductor nanowires is developed, which enables one to determine the growth conditions under which the formation of nanowires is possible. General expression for the nanowire growth rate as function of its radius and the growth conditions is obtained and analy...
[Phys. Rev. B 78, 235301] Published Mon Dec 01, 2008
- Dynamic Jahn-Teller effect in electronic transport through single C_{60} molecules
Author(s): Thomas Frederiksen, Katharina J. Franke, Andrés Arnau, Gunnar Schulze, Jose Ignacio Pascual, and Nicolás Lorente
Low-temperature scanning tunneling spectroscopy and first-principles calculations are used to characterize electron transport through vibronic states of C_{60} molecules. This is achieved by positioning a C_{60} molecule on top of a molecular self-assembled template on Au(111). In these conditions, ...
[Phys. Rev. B 78, 233401] Published Mon Dec 01, 2008
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