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1.	Larson, Jonas, et al. (författare) Spin-orbit-coupled Bose-Einstein condensate in a tilted optical lattice 2010 Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - : APS. - 1050-2947 .- 1094-1622. ; 82:4, s. 043620- Tidskriftsartikel (refereegranskat)abstract Bloch oscillations appear for a particle in a weakly tilted periodic potential. The intrinsic spin Hall effect is an outcome of a spin-orbit coupling. We demonstrate that both of these phenomena can be realized simultaneously in a gas of weakly interacting ultracold atoms exposed to a tilted optical lattice and to a set of spatially dependent light fields inducing an effective spin-orbit coupling. It is found that both the spin Hall and the Bloch oscillation effects may coexist, showing, however, a strong correlation between the two. These correlations are manifested as a transverse spin current oscillating in-phase with the Bloch oscillations. On top of the oscillations originating from the periodicity of the model, a trembling motion is found which is believed to be atomic Zitterbewegung. It is argued that the damping of these Zitterbewegung oscillations may to a large extent be prevented in the present setup considering a periodic optical lattice potential.
2.	Ali, M., et al. (författare) Reduced photoluminescence from InGaN/GaN multiple quantum well structures following 40 MeV iodine ion irradiation 2009 Ingår i: Physica. B, Condensed matter. - : Elsevier. - 0921-4526 .- 1873-2135. ; 404:23-24, s. 4925-4928 Tidskriftsartikel (refereegranskat)abstract The effects following ion irradiation of GaN-based devices are still limited. Here we present data on the photoluminescence (PL) emitted from InGaN/GaN multiple quantum well (MQW) structures, which have been exposed to 40 MeV I ion irradiation. The PL is reduced as a function of applied ion fluence, with essentially no PL signal left above 1011 ions/cm2. It is observed that even the ion fluences in the 109 ions/cm2 range have a pronounced effect on the photoluminescence properties of the MQW structures. This may have consequences concerning application of InGaN/GaN MQW’s in radiation-rich environments, in addition to defect build-up during ion beam analysis.
3.	Colarieti-Tosti, M., et al. (författare) On the magnetic anisotropy of Gd metal 2003 Ingår i: Physical Review Letters. ; 91:15 Tidskriftsartikel (refereegranskat)
4.	Waltersson, Erik, 1979-, et al. (författare) Controlled operations in a strongly correlated two-electron quantum ring 2009 Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 79:11, s. 115318- Tidskriftsartikel (refereegranskat)abstract We have analyzed the electronic spectrum and wave-function characteristics of a strongly correlated two-electron quantum ring with model parameters close to those observed in experiments. The analysis is based on an exact diagonalization of the Hamiltonian in a large B-spline basis. We propose a qubit pair for storing quantum information, where one component is stored in the total electron spin and one multivalued “quMbit” is represented by the total angular momentum. In this scheme the controlled-NOT quantum gate is demonstrated with near 100% fidelity for a realistic far-infrared electromagnetic pulse.
5.	Manzetti, Sergio, et al. (författare) A Korteweg-DeVries type model for helical soliton solutions for quantum and continuum phenomena 2021 Ingår i: International Journal of Modern Physics C. - : World Scientific. - 0129-1831. ; 32:03 Tidskriftsartikel (refereegranskat)abstract Quantum mechanical states are normally described by the Schrödinger equation, which generates real eigenvalues and quantizable solutions which form a basis for the estimation of quantum mechanical observables, such as momentum and kinetic energy. Studying transition in the realm of quantum physics and continuum physics is however more difficult and requires different models. We present here a new equation which bears similarities to the Korteweg–DeVries (KdV) equation and we generate a description of transitions in physics. We describe here the two- and three-dimensional form of the KdV like model dependent on the Plank constant ℏ and generate soliton solutions. The results suggest that transitions are represented by soliton solutions which arrange in a spiral-fashion. By helicity, we propose a conserved pattern of transition at all levels of physics, from quantum physics to macroscopic continuum physics.
6.	Rammer, Jörgen, 1952- (författare) Quantum field theory of non-equilibrium states 2007 Bok (refereegranskat)
7.	Bleskov, I. D., et al. (författare) Ab initio calculations of elastic properties of Ru1-xNixAl superalloys 2009 Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 94:16 Tidskriftsartikel (refereegranskat)abstract Ab initio total energy calculations based on the exact muffin-tin orbitals method, combined with the coherent potential approximation, have been used to study the thermodynamical and elastic properties of substitutional refractory Ru1-xNixAl alloys. We have found that the elastic constants C' and C11 exhibit pronounced peculiarities near the concentration of about 40 at. % Ni, which we ascribe to electronic topological transitions. Our suggestion is supported by the Fermi surface calculations in the whole concentration range. Results of our calculations show that one can design Ru-Ni-Al alloys substituting Ru by Ni (up to 40 at. %) with almost invariable elastic constants and reduced density.
8.	Baggioli, Matteo, et al. (författare) Holographic plasmon relaxation with and without broken translations 2019 Ingår i: Journal of High Energy Physics (JHEP). - : SPRINGER. - 1126-6708 .- 1029-8479. ; :9 Tidskriftsartikel (refereegranskat)abstract We study the dynamics and the relaxation of bulk plasmons in strongly coupled and quantum critical systems using the holographic framework. We analyze the dispersion relation of the plasmonic modes in detail for an illustrative class of holographic bottom-up models. Comparing to a simple hydrodynamic formula, we entangle the complicated interplay between the three least damped modes and shed light on the underlying physical processes. Such as the dependence of the plasma frequency and the effective relaxation time in terms of the electromagnetic coupling, the charge and the temperature of the system. Introducing momentum dissipation, we then identify its additional contribution to the damping. Finally, we consider the spontaneous symmetry breaking (SSB) of translational invariance. Upon dialing the strength of the SSB, we observe an increase of the longitudinal sound speed controlled by the elastic moduli and a decrease in the plasma frequency of the gapped plasmon. We comment on the condensed matter interpretation of this mechanism.
9.	Grigoriev, Anton, et al. (författare) Electron transport in stretched monoatomic gold wires 2006 Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 97, s. 236807- Tidskriftsartikel (refereegranskat)abstract The conductance of monoatomic gold wires containing 3-7 gold atoms has been obtained from ab initio calculations. The transmission is found to vary significantly depending on the wire stretching and the number of incorporated atoms. Such oscillations are determined by the electronic structure of the one-dimensional (1D) part of the wire between the contacts. Our results indicate that the conductivity of 1D wires can be suppressed without breaking the contact.
10.	Elenius, Måns, 1974-, et al. (författare) Evidence for a liquid-solid critical point in a simple monatomic system 2009 Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 131:104502 Tidskriftsartikel (refereegranskat)abstract It is commonly believed that the transition line separating a liquid and a solid cannot be interrupted by a critical point. This opinion is based on the traditional symmetry argument that an isotropic liquid cannot be continuously transformed into a crystal with a discrete rotational and translational symmetry. We present here a molecular-dynamics simulation of a simple monatomic system suggesting the existence of a liquid-solid spinodal terminating at a critical point. We show that, in the critical region, the isotropic liquid continuously transforms into a phase with a mesoscopic order similar to that of the smectic liquid crystals. We argue that the existence of both the spinodal and the critical point can be explained by the close structural proximity between the mesophase and the crystal. This indicates a possibility of finding a similar thermodynamic behaviour in gelating colloids, liquid crystals and polymers.
11.	Bahrova, O. M., et al. (författare) Cooling of nanomechanical vibrations by Andreev injection 2022 Ingår i: Low Temperature Physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 48:6, s. 476-482 Tidskriftsartikel (refereegranskat)abstract A nanoelectromechanical weak link composed of a carbon nanotube suspended between two normal electrodes in a gap between two superconducting leads is considered. The nanotube is treated as a movable single level quantum dot in which the position-dependent superconducting order parameter is induced due to the Cooper pair tunneling. We show that electron tunneling processes significantly affect the state of the mechanical subsystem. We found that at a given direction of the applied voltage between the electrodes, the stationary state of the mechanical subsystem has a Boltzmann form with an effective temperature dependent on the parameters of the device. As this takes place, the effective temperature can reach significantly small values (cooling effect). We also demonstrate that nanotube fluctuations strongly affect the dc current through the system. The latter can be used to probe the predicted effects in an experiment. Published under an exclusive license by AIP Publishing.
12.	Gran, Ulf, 1973, et al. (författare) Plasmons in holographic graphene 2020 Ingår i: SciPost Physics. - : SCIPOST FOUNDATION. - 2542-4653. ; 8:6 Tidskriftsartikel (refereegranskat)abstract We demonstrate how self-sourced collective modes - of which the plasmon is a prominent example due to its relevance in modern technological applications - are identified in strongly correlated systems described by holographic Maxwell theories. The characteristic ω ∝ pk plasmon dispersion for 2D materials, such as graphene, naturally emerges from this formalism. We also demonstrate this by constructing the first holographic model containing this feature. This provides new insight into modeling such systems from a holographic point of view, bottom-up and top-down alike. Beyond that, this method provides a general framework to compute the dynamical charge response of strange metals, which has recently become experimentally accessible due to the novel technique of momentum-resolved electron energy-loss spectroscopy (M-EELS). This framework therefore opens up the exciting possibility of testing holographic models for strange metals against actual experimental data.
13.	Jiao, Yang, 1985, et al. (författare) Signatures of van der Waals binding: A coupling-constant scaling analysis 2018 Ingår i: Physical Review B. - 2469-9969 .- 2469-9950. ; 97:8 Tidskriftsartikel (refereegranskat)abstract The van der Waals (vdW) density functional (vdW-DF) method [Rep. Prog. Phys. 78, 066501 (2015)RPPHAG0034-488510.1088/0034-4885/78/6/066501] describes dispersion or vdW binding by tracking the effects of an electrodynamic coupling among pairs of electrons and their associated exchange-correlation holes. This is done in a nonlocal-correlation energy term Ecnl, which permits density functional theory calculation in the Kohn-Sham scheme. However, to map the nature of vdW forces in a fully interacting materials system, it is necessary to also account for associated kinetic-correlation energy effects. Here, we present a coupling-constant scaling analysis, which permits us to compute the kinetic-correlation energy Tcnl that is specific to the vdW-DF account of nonlocal correlations. We thus provide a more complete spatially resolved analysis of the electrodynamical-coupling nature of nonlocal-correlation binding, including vdW attraction, in both covalently and noncovalently bonded systems. We find that kinetic-correlation energy effects play a significant role in the account of vdW or dispersion interactions among molecules. Furthermore, our mapping shows that the total nonlocal-correlation binding is concentrated to pockets in the sparse electron distribution located between the material fragments.
14.	Klacar, Simon, 1984 (författare) Chemical Properties of Oxidized Silver - A Density Functional Theory Study 2011 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)
15.	Parafilo, A. V., et al. (författare) Pumping and Cooling of Nanomechanical Vibrations Generated by Cooper-Pair Exchange 2022 Ingår i: Journal of Low Temperature Physics. - : Springer Science and Business Media LLC. - 0022-2291 .- 1573-7357. ; 210:1-2, s. 150-65 Tidskriftsartikel (refereegranskat)abstract We consider a nanoelectromechanical system composed of a carbon nanotube suspended between two normal leads and coupled to a superconducting scanning tunneling microscope (STM) tip via vacuum tunnel barrier. Treating the nanotube as a single-level quantum dot, it is shown that an applied voltage between the superconducting STM tip and normal leads gives rise to a pumping or a cooling of the mechanical subsystem depending on the direction of the electronic flow. It is also demonstrated that the transition between these two regimes is controlled by the strength of the tunnel coupling between the nanotube and superconducting STM tip and the relative position of the electronic level. Such phenomena are realized due to a specific electromechanical coupling that is fully governed by the quantum dynamics of the Cooper pairs. The amplitude of the self-sustained oscillations in the pumping regime is analyzed numerically, and the effective temperature of the mechanical subsystem in the cooling regime is obtained.
16.	Sjöqvist, Erik, et al. (författare) Conceptual aspects of geometric quantum computation 2016 Ingår i: Quantum Information Processing. - : Springer Science and Business Media LLC. - 1570-0755 .- 1573-1332. ; 15:10, s. 3995-4011 Tidskriftsartikel (refereegranskat)abstract Geometric quantum computation is the idea that geometric phases can be used to implement quantum gates, i.e., the basic elements of the Boolean network that forms a quantum computer. Although originally thought to be limited to adiabatic evolution, controlled by slowly changing parameters, this form of quantum computation can as well be realized at high speed by using nonadiabatic schemes. Recent advances in quantum gate technology have allowed for experimental demonstrations of different types of geometric gates in adiabatic and nonadiabatic evolution. Here, we address some conceptual issues that arise in the realizations of geometric gates. We examine the appearance of dynamical phases in quantum evolution and point out that not all dynamical phases need to be compensated for in geometric quantum computation. We delineate the relation between Abelian and non-Abelian geometric gates, and find an explicit physical example where the two types of gates coincide. We identify differencies and similarities between adiabatic and nonadiabatic realizations of quantum computation based on non-Abelian geometric phases.
17.	Azimi Mousolou, Vahid, et al. (författare) Universal Non-adiabatic Holonomic Gates in Quantum Dots and Single-Molecule Magnets 2014 Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 16 Tidskriftsartikel (refereegranskat)abstract Geometric manipulation of a quantum system offers a method for fast, universal, and robust quantum information processing. Here, we propose a scheme for universal all-geometric quantum computation using non-adiabatic quantum holonomies. We propose three different realizations of the scheme based on an unconventional use of quantum dot and single-molecule magnet devices, which offer promising scalability and robust efficiency.
18.	Scheicher, Ralph H., et al. (författare) Theoretical study of C60 as catalyst for dehydrogenation in LiBH4 2011 Ingår i: Nanotechnology. - UK : Institute of Physics. - 0957-4484 .- 1361-6528. ; 22:33 Tidskriftsartikel (refereegranskat)abstract Complex light metal hydrides possess many properties which make them attractive as a storage medium for hydrogen, but typically catalysts are required to lower the hydrogen desorption temperature and to facilitate hydrogen uptake in the form of a reversible reaction. The overwhelming focus in the search for catalysing agents has been on compounds containing titanium, but the precise mechanism of their actions remains somewhat obscure. A recent experiment has now shown that fullerenes (C60) can also act as catalysts for both hydrogen uptake and release in lithium borohydride (LiBH4). In an effort to understand the involved mechanism, we have employed density functional theory to carry out a detailed study of the interaction between this complex metal hydride and the carbon nanomaterial. Considering a stepwise reduction of the hydrogen content in LiBH4, we find that the presence of C60 can lead to a substantial reduction of the involved H-removal energies. This effect is explained as a consequence of the interaction between the BHx − complex and the C60 entity.
19.	Catena, Riccardo, 1978, et al. (författare) Dark matter-electron interactions in materials beyond the dark photon model 2023 Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; 2023:3 Tidskriftsartikel (refereegranskat)abstract The search for sub-GeV dark matter (DM) particles via electronic transitions in underground detectors attracted much theoretical and experimental interest in the past few years. A still open question in this field is whether experimental results can in general be interpreted in a framework where the response of detector materials to an external DM probe is described by a single ionisation or crystal form factor, as expected for the so-called dark photon model. Here, ionisation and crystal form factors are examples of material response functions: interaction-specific integrals of the initial and final state electron wave functions. In this work, we address this question through a systematic classification of the material response functions induced by a wide range of models for spin-0, spin-1/2 and spin-1 DM. We find several examples for which an accurate description of the electronic transition rate at DM direct detection experiments requires material response functions that go beyond those expected for the dark photon model. This concretely illustrates the limitations of a framework that is entirely based on the standard ionisation and crystal form factors, and points towards the need for the general response-function-based formalism we pushed forward recently [1,2]. For the models that require non-standard atomic and crystal response functions, we use the response functions of [1,2] to calculate the DM-induced electronic transition rate in atomic and crystal detectors, and to present 90% confidence level exclusion limits on the strength of the DM-electron interaction from the null results reported by XENON10, XENON1T, EDELWEISS and SENSEI.
20.	Proceedings of the 11th European Conference on Thermophysical Properties (ECTP-11), Umeå, Sweden, 13-16 June 1988 1989 Proceedings (redaktörskap) (populärvet., debatt m.m.)
21.	Magnuson, Martin, et al. (författare) Electronic structure and chemical bonding of nanocrystalline-TiC/amorphous-C nanocomposites 2009 Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 80:235108 Tidskriftsartikel (refereegranskat)abstract The electronic structure of nanocrystalline (nc-) TiC/amorphous C nanocomposites has been investigated bysoft x-ray absorption and emission spectroscopy. The measured spectra at the Ti 2p and C 1s thresholds of thenanocomposites are compared to those of Ti metal and amorphous C. The corresponding intensities of theelectronic states for the valence and conduction bands in the nanocomposites are shown to strongly depend onthe TiC carbide grain size. An increased charge transfer between the Ti 3d-eg states and the C 2p states hasbeen identified as the grain size decreases, causing an increased ionicity of the TiC nanocrystallites. It issuggested that the charge transfer occurs at the interface between the nanocrystalline-TiC and the amorphous-Cmatrix and represents an interface bonding which may be essential for the understanding of the properties ofnc-TiC/amorphous C and similar nanocomposites.
22.	Ahrentorp, Fredrik, et al. (författare) Sensitive magnetic biodetection using magnetic multi-core nanoparticles and RCA coils 2017 Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 427, s. 14-18 Tidskriftsartikel (refereegranskat)abstract We use functionalized iron oxide magnetic multi-core particles of 100 nm in size (hydrodynamic particle diameter) and AC susceptometry (ACS) methods to measure the binding reactions between the magnetic nanoparticles (MNPs) and bio-analyte products produced from DNA segments using the rolling circle amplification (RCA) method. We use sensitive induction detection techniques in order to measure the ACS response. The DNA is amplified via RCA to generate RCA coils with a specific size that is dependent on the amplification time. After about 75 min of amplification we obtain an average RCA coil diameter of about 1 mu m. We determine a theoretical limit of detection (LOD) in the range of 11 attomole (corresponding to an analyte concentration of 55 fM for a sample volume of 200 mu L) from the ACS dynamic response after the MNPs have bound to the RCA coils and the measured ACS readout noise. We also discuss further possible improvements of the LOD.
23.	Rammer, Jörgen, 1952- (författare) Quantum field theory of non-equilibrium states 2010. - China Bok (refereegranskat)
24.	Mamontov, Eugen, 1955 (författare) Ordinary differential equation system for population of individuals and the corresponding probabilistic model 2008 Ingår i: Mathl. Computer Modelling. - : Elsevier BV. - 0895-7177. Tidskriftsartikel (refereegranskat)abstract The key model for particle populations in statistical mechanics is the Bogolyubov–Born– Green–Kirkwood–Yvon (BBGKY) equation chain. It is derived mainly from the Hamilton ordinary differential equation (ODE) system for the vectors of the particle states in the particle position-momentum phase space. Many problems beyond physics or chemistry, for instance, in the living-matter sciences (biology, medicine, ecology, and scoiology) make it necessary to extend the notion of a particle to an individual, or active particle. This challenge is met by the generalized kinetic theory. It implements the extension by extending the phase space from the space of the position-momentum vectors to more rich spaces formed by the state vectors with the entries which need not be limited to the entries of the position and momentum: they include other scalar variables (e.g., those associated with modelling homeorhesis or other features inherent to the individuals). One can assume that the dynamics of the state vector in the extended space, i.e. the states of the individuals (rather than common particles) is also described by an ODE system. The latter, however, need not be the Hamilton one. The question is how one can derive the analogue of the BBGKY paradigm for the new settings. The present work proposes an answer to this question. It applies a very limited number of carefully selected tools of probability theory and common statistical mechanics. It in particular uses the well-known feature that the maximum number of the individuals which can mutually interact simultaneously is bounded by a fixed value of a few units. The present approach results in the finite system of equations for the reduced many-individual distribution functions thereby eliminating the so-called closure problem inevitable in the BBGKY theory. The thermodynamic-limit assumption is not needed either. The system includes consistently derived terms of all of the basic types known in kinetic theory, in particular, both the “mean-field” and scattering-integral terms, and admits the kinetic equation of the form allowing a direct chemical-reaction reading. The present approach can deal with Hamilton’s equation systems which are nonmonogenic and not treated in statistical mechanics. The proposed modelling suggests the basis of the generalized kinetic theory and may serve as the stochastic mechanics of population of individuals.
25.	Castelain, Mickaël, et al. (författare) Fast uncoiling kinetics of F1C pili expressed by uropathogenic Escherichia coli are revealed on a single pilus level using force-measuring optical tweezers 2011 Ingår i: European Biophysics Journal. - : Springer Science and Business Media LLC. - 0175-7571 .- 1432-1017. ; 40:3, s. 305-316 Tidskriftsartikel (refereegranskat)abstract Uropathogenic Escherichia coli (UPEC) expressvarious kinds of organelles, so-called pili or fimbriae, thatmediate adhesion to host tissue in the urinary tract throughspecific receptor-adhesin interactions. The biomechanicalproperties of these pili have been considered important forthe ability of bacteria to withstand shear forces from rinsingurine flows. Force-measuring optical tweezers have beenused to characterize individual organelles of F1C typeexpressed by UPEC bacteria with respect to such properties.Qualitatively, the force-versus-elongation response wasfound to be similar to that of other types of helix-like piliexpressed by UPEC, i.e., type 1, P, and S, with force-inducedelongation in three regions, one of which represents theimportant uncoiling mechanism of the helix-like quaternarystructure. Quantitatively, the steady-state uncoiling forcewas assessed as 26.4 ±1.4 pN, which is similar to those ofother pili (which range from 21 pN for SI to 30 pN for type 1).The corner velocity for dynamic response (1,400 nm/s) wasfound to be larger than those of the other pili (400–700 nm/sfor S and P pili, and 6 nm/s for type 1). The kinetics werefound to be faster, with a thermal opening rate of 17 Hz, afew times higher than S and P pili, and three orders ofmagnitude higher than type 1. These data suggest that F1Cpili are, like P and S pili, evolutionarily selected to primarilywithstand the conditions expressed in the upper urinary tract.
26.	Erhart, Paul, 1978 (författare) A first-principles study of helium storage in oxides and at oxide-iron interfaces 2012 Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 111:11 Tidskriftsartikel (refereegranskat)abstract Density-functional theory calculations based on conventional as well as hybrid exchange-correlation functionals have been carried out to study the properties of helium in various oxides (Al2O3, TiO2, Y2O3, YAP, YAG, YAM, MgO, CaO, BaO, SrO) as well as at oxide-iron interfaces. Helium interstitials in bulk oxides are shown to be energetically more favorable than substitutional helium, yet helium binds to existing vacancies. The solubility of He in oxides is systematically higher than in iron and scales with the free volume at the interstitial site nearly independently of the chemical composition of the oxide. In most oxides, He migration is significantly slower and He-He binding is much weaker than in iron. To quantify the solubility of helium at oxide-iron interfaces two prototypical systems are considered (Fe-MgO, Fe-FeO-MgO). In both cases, the He solubility is markedly enhanced in the interface compared to either of the bulk phases. The results of the calculations allow to construct a schematic energy landscape for He interstitials in iron. The implications of these results are discussed in the context of helium sequestration in oxide dispersion strengthened steels, including the effects of interfaces and lattice strain.
27.	Parafilo, A. V., et al. (författare) Kondo effect in a Aharonov-Casher interferometer 2019 Ingår i: Physical Review B. - 2469-9950 .- 2469-9969. ; 100:23 Tidskriftsartikel (refereegranskat)abstract We consider a model describing a spin field-effect transistor based on a quantum nanowire with a tunable spin-orbit interaction embedded between two ferromagnetic leads with anticollinear magnetization. We investigate a regime of a strong interplay between resonance Kondo scattering and interference associated with the Aharonov-Casher effect. Using the Keldysh technique at a weak-coupling regime we calculate perturbatively the charge current. It is predicted that the effects of the spin-orbit interaction result in a nonvanishing current for any spin polarization of the leads including the case of fully polarized anticollinear contacts. We analyze the influence of the Aharonov-Casher phase and degree of spin polarization in the leads onto a Kondo temperature.
28.	Radic, D., et al. (författare) Nanomechanical cat states generated by a dc voltage-driven Cooper pair box qubit 2022 Ingår i: npj Quantum Information. - : Springer Science and Business Media LLC. - 2056-6387. ; 8:1 Tidskriftsartikel (refereegranskat)abstract We study a nanoelectromechanical system consisting of a Cooper pair box qubit performing nanomechanical vibrations between two bulk superconductors. We demonstrate that a bias voltage applied to the superconductors may generate states represented by entanglement between qubit states and quantum 'cat states', i.e. a superposition of the coherent states of the nanomechanical oscillator. We characterize the formation and development of such states in terms of the corresponding Wigner function and entropy of entanglement. Also, we propose an experimentally feasible detection scheme for the effect, in which the average current that attains the specific features created by the entanglement is measured.
29.	Fan, Qunping, 1989, et al. (författare) Over 14% efficiency all-polymer solar cells enabled by a low bandgap polymer acceptor with low energy loss and efficient charge separation 2020 Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry. - 1754-5692 .- 1754-5706. ; 13:12, s. 5017-5027 Tidskriftsartikel (refereegranskat)abstract Obtaining both high open-circuit voltage (V-oc) and short-circuit current density (J(sc)) has been a major challenge for efficient all-polymer solar cells (all-PSCs). Herein, we developed a polymer acceptor PF5-Y5 with excellent optical absorption capability (onset extending to similar to 880 nm and maximum absorption coefficient exceeding 105 cm(-1) in a film), high electron mobility (3.18 x 10(3) cm(2) V-1 s(-1)) and high LUMO level (-3.84 eV) to address such a challenge. As a result, the PBDB-T:PF5-Y5-based all-PSCs achieved a high power conversion efficiency of up to 14.45% with both a high Voc (0.946 V) and a high Jsc (20.65 mA cm(-2)), due to the high and broad absorption coverage, small energy loss (0.57 eV) and efficient charge separation and transport in the device, which are among the best values in the all-PSC field. In addition, the all-PSC shows a similar to 15% improvement in PCE compared to its counterpart small molecule acceptor (Y5)-based device. Our results suggest that PF5-Y5 is a very promising polymer acceptor candidate for applications in efficient all-PSCs.
30.	Wei, Yajun, et al. (författare) Magnetic coupling in asymmetric FeCoV/Ru/FeNi trilayers 2014 Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. Konferensbidrag (refereegranskat)abstract We have investigated the magnetic anisotropy and interlayer coupling in trilayer films of permendur(100 angstrom)/Ru/permalloy(100 angstrom), with the thickness of the Ru spacer varying from 0 to 200 angstrom. While the permendur/permalloy sample exhibits a small in-plane uniaxial magnetic anisotropy with H-u = 27 Oe, all trilayers are magnetically isotropic in-plane. Results from hysteresis loop and ferromagnetic resonance measurements were fitted to a micromagnetic model, with the results indicating that all the films are ferromagnetically coupled except the one with 10 angstrom Ru spacer, which shows antiferromagnetic coupling. The trilayers with Ru spacer layer thickness larger than 20 angstrom exhibit only very weak ferromagnetic coupling. (C) 2014 AIP Publishing LLC.
31.	Klacar, Simon, 1984 (författare) First Principles Calculations for NOx Reduction over Ag/Al2O3 2013 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)
32.	Londero, Elisa, 1982, et al. (författare) Desorption of n-alkanes from graphene: a van der Waals density functional study 2012 Ingår i: Journal of Physics Condensed Matter. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 24:42, s. 424212- Tidskriftsartikel (refereegranskat)abstract A recent study of temperature-programmed desorption (TPD) measurements of small linear alkane molecules (n-alkanes, with formula CNH2N+2) from C(0001) deposited on Pt(111) shows a linear relationship of the desorption energy with increasing n-alkane chain length N. We here present a van der Waals density functional study of the desorption barrier energy of the ten smallest n-alkanes (of carbon chain length N = 1–10) from graphene. We find linear scaling with N, including a non-zero intercept with the energy axis, i.e. an offset at the extrapolation to N = 0. This calculated offset is quantitatively similar to the results of the TPD measurements. From further calculations of the polyethylene polymer we offer a suggestion for the origin of the offset.
33.	Su, Wenyan, et al. (författare) Nonconjugated Terpolymer Acceptors with Two Different Fused-Ring Electron-Deficient Building Blocks for Efficient All-Polymer Solar Cells 2021 Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 13:5, s. 6442-6449 Tidskriftsartikel (refereegranskat)abstract The ternary polymerization strategy of incorporating different donor and acceptor units forming terpolymers as photovoltaic materials has been proven advantageous in improving power conversion efficiencies (PCEs) of polymer solar cells (PSCs). Herein, a series of low band gap nonconjugated terpolymer acceptors based on two different fused-ring electron-deficient building blocks (IDIC16 and ITIC) with adjustable photoelectric properties were developed. As the third component, ITIC building blocks with a larger pi-conjugation structure, shorter solubilizing side chains, and red-shifted absorption spectrum were incorporated into an IDIC16-based nonconjugated copolymer acceptor PF1-TS4, which built up the terpolymers with two conjugated building blocks linked by flexible thioalkyl chain-thiophene segments. With the increasing ITIC content, terpolymers show gradually broadened absorption spectra and slightly down-shifted lowest unoccupied molecular orbital levels. The active layer based on terpolymer PF1-TS4-60 with a 60% ITIC unit presents more balanced hole and electron mobilities, higher photoluminescence quenching efficiency, and improved morphology compared to those based on PF1-TS4. In all-polymer solar cells (all-PSCs), PF1-TS4-60, matched with a wide band gap polymer donor PM6, achieved a similar open-circuit voltage (V-oc) of 0.99 V, a dramatically increased short-circuit current density (J(sc)) of 15.30 mA cm(-2), and fill factor (FF) of 61.4% compared to PF1-TS4 = 0.99 V, J(sc) = 11.21 mA cm(-2), and FF = 55.6%). As a result, the PF1-TS4-60-based all-PSCs achieved a PCE of 9.31%, which is similar to 50% higher than the PF1-TS4-based ones (6.17%). The results demonstrate a promising approach to develop high-performance nonconjugated terpolymer acceptors for efficient all-PSCs by means of ternary polymerization using two different A-D-A-structured fused-ring electron-deficient building blocks.
34.	Andersson, David A., et al. (författare) First-principles based calculation of binary and multicomponent phase diagrams for titanium carbonitride 2008 Ingår i: Calphad. - : Elsevier BV. - 0364-5916 .- 1873-2984. ; 32:3, s. 543-565 Forskningsöversikt (refereegranskat)abstract In this paper we have used a combined first principles and Calphad approach to calculate phase diagrams in the titanium-carbon-nitrogen system, with particular focus on the vacancy-induced ordering of the substoichiometric carbonitride phase, TiCxNy (x + y <= 1). Results from earlier Monte Carlo simulations of the low-temperature binary phase diagrams are used in order to formulate sublattice models for TiCxNy within the compound energy formalism (CEF) that are capable of describing both the low temperature ordered and the high-temperature disordered state. We parameterize these models using first-principles calculations and then we demonstrate how they can be merged with thermodynamic descriptions of the remaining Ti-C-N phases that are derived within the Calphad method by fitting model parameters to experimental data. We also discuss structural and electronic properties of the ordered end-member compounds, as well as short range order effects in the TiCxNy phase.
35.	Gran, Ulf, 1973, et al. (författare) Holographic response of electron clouds 2019 Ingår i: Journal of High Energy Physics. - : SPRINGER. - 1029-8479 .- 1126-6708. ; 2019:3 Tidskriftsartikel (refereegranskat)abstract In order to make progress towards more realistic models of holographic fermion physics, we use gauge/gravity duality to compute the dispersion relations for quasinormal modes and collective modes for the electron cloud background, i.e. the non-zero temperature version of the electron star. The results are compared to the corresponding results for the Schwarzschild and Reissner-Nordstrom black hole backgrounds, and the qualitative differences are highlighted and discussed.
36.	Al-Zoubi, Noura, et al. (författare) Influence of Magnesium on hydrogenated ScAl1-xMgx alloys : a theoretical study 2011 Ingår i: Computational materials science. - : Elsevier BV. - 0927-0256 .- 1879-0801. ; 50:10, s. 2848-2853 Tidskriftsartikel (refereegranskat)abstract Ab initio total energy calculations, based on the projector augmented wave method and the exact mu±n-tin orbitals method in combination with the coherent-potential approximation, are used to examine the effect of magnesium on hydrogen absorption/desorption temperature and phase stability of hydrogenated ScAl1-xMgx (0 ≤ x ≤ 0:3) alloys. According to the experiments, ScAl1-xMgx adopts the CsCl structure, and upon hydrogen absorption it decomposes into ScH2 with CaF2 structure and Al-Mg with face centered cubic structure. Here we demonstrate that the stability field of the hydrogenated alloys depends sensitively on Mg content and on the microstructure of the decomposed system. For a given microstructure, the critical temperature for hydrogen absorption/desorption increases with Mg concentration.
37.	Al-Zoubi, Noura, et al. (författare) The bain path of paramagnetic Fe-Cr based alloys 2011 Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 110:1, s. 013708- Tidskriftsartikel (refereegranskat)abstract Employing the first-principles exact muffin-tin orbital method in combination with the coherent potential approximation, we calculated the total energy and local magnetic moments of paramagnetic Fe-Cr-M (M = Cr, Mn, Fe, Co, Ni) alloys along the tetragonal distortion (Bain) path connecting the body centered cubic (bcc) and the face centered cubic (fcc) structures. The paramagnetic phase is modeled by the disordered local magnetic moment scheme. For all alloys, the local magnetic moments on Fe atoms decrease from the maximum value corresponding to the bcc phase toward the minimum value realized for the fcc phase. Cobalt atoms have non-vanishing local magnetic moments only for tetragonal lattices with c/a < 1.30, whereas the local magnetic moments of Mn show weak crystal structure dependence. We find that Cr stabilizes the bcc lattice and increases the energy barrier as going from the bcc toward the fcc phase. Both Co and Ni favor the fcc lattice and decrease the energy barrier relative to the bcc phase. On the other hand, the tetragonal distortion around the fcc phase is facilitated by Cr and to a somewhat lesser extent also by Ni, but strongly impeded by Co. Manganese has negligible effect on the structural energy difference as well as on the energy barrier along the Bain path. Our findings on the alloying induced softening or hardening of Fe-Cr based alloys against tetragonal distortions are important for understanding the interstitial driven martensitic transformations in alloy steels.
38.	Beiuseanu, F., et al. (författare) Absence of half-metallicity in defect-free digital magnetic heterostructures delta-doped with Cr and Mn 2011 Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 83:12, s. 125107- Tidskriftsartikel (refereegranskat)abstract We present the results of combined density functional and many-body calculations of the electronic and magnetic properties of the defect-free digital ferromagnetic heterostructures obtained by doping GaAs with Cr and Mn. While the local-density approximation +U predicts half-metallicity in these defect-free delta-doped heterostructures, we demonstrate that local many-body correlations captured by dynamical mean-field theory induce within the minority-spin channel nonquasiparticle states just above E-F. As a consequence of the existence of these many-body states the half-metallic gap is closed and the carriers' spin polarization is significantly reduced. Below the Fermi level the minority-spin highest valence states are found to localize more on the GaAs layers, being independent of the type of electronic correlations considered. Thus, our results confirm the confinement of carriers in these delta-doped heterostructures, having a spin polarization that follows a different temperature dependence than the magnetization. We suggest that polarized hot-electron photoluminescence experiments might uncover evidence for the existence of many-body states within the minority-spin channel and elucidate their finite-temperature behavior.
39.	Berntsen, P., et al. (författare) Complex modulus and compliance for airway smooth muscle cells 2020 Ingår i: Physical Review E. - 2470-0045 .- 2470-0053. ; 101:3 Tidskriftsartikel (refereegranskat)abstract A cell can be described as a complex viscoelastic material with structural relaxations that is modulated by thermal and chemically nonequilibrium processes. Tissue morphology and function rely upon cells' physical responses to mechanical force. We measured the frequency-dependent mechanical relaxation response of adherent human airway smooth muscle cells under adenosine triphosphate (ATP) depletion and normal ATP conditions. The frequency dependence of the complex compliance J* and modulus G* was measured over the frequencies 10(-1) < f < 10(3) Hz at selected temperatures between 4 < T < 54 degrees C. Our results show characteristic relaxation features which can be interpreted by the mode-coupling theory (MCT) of viscoelastic liquids. We analyze the shape of the spectra in terms of a so-called A(4) scenario with logarithmic scaling laws. Characteristic timescales tau(beta) and tau(alpha) appear with corresponding energy barriers E-beta approximate to (10-20)k(B) T and E-alpha approximate to (20-30)k(B)T. We demonstrate that cells are close to a glass transition. We find that the cell becomes softer around physiological temperatures, where its surface structure is more liquid-like with a plateau modulus around 0.1-0.8 kPa compared with the more solid-like interior cytoskeletal structures with a plateau modulus 1-15 kPa. Corresponding values for the viscosity are 10(2)-10(3) Pa s for the surface structures closer to the membrane and 10(4)-10(6) Pa s for the core cytoskeletal structures.
40.	Bylander, Jonas, 1978 (författare) Writing to Learn Quantum Engineering: Improved Understanding and Communication by Revising a Writing Assignment 2016 Ingår i: KUL2016 Konferens om Undervisning och Lärande på Chalmers. ; Extended Abstracts Konferensbidrag (refereegranskat)abstract I present an improved lab-report writing assignment for formative assessment in master’s-level physics. Prompted by poorly written reports in an earlier version of the course, suggesting insufficient subject understanding, I aligned aims, learning objectives, instruction, and assessment, and introduced a component of student peer review. This method enhanced learning of the subject matter, indicated by clearly improved reports.
41.	Castleton, Christopher, 1969-, et al. (författare) Managing the supercell approximation for charged defects in semiconductors : Finite-size scaling, charge correction factors, the band-gap problem, and the ab initio dielectric constant 2006 Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 73:035215, s. 11- Tidskriftsartikel (refereegranskat)abstract The errors arising in ab initio density functional theory studies of semiconductor point defects using the supercell approximation are analyzed. It is demonstrated that (a) the leading finite size errors are inverse linear and inverse cubic in the supercell size and (b) finite size scaling over a series of supercells gives reliable isolated charged defect formation energies to around +-0.05 eV. The scaled results are used to test three correction methods. The Makov-Payne method is insufficient, but combined with the scaling parameters yields an ab initio dielectric constant of 11.6+-4.1 for InP. Gamma point corrections for defect level dispersion are completely incorrect, even for shallow levels, but realigning the total potential in real-space between defect and bulk cells actually corrects the electrostatic defect-defect interaction errors as well. Isolated defect energies to +-0.1 eV are then obtained using a 64 atom supercell, though this does not improve for larger cells. Finally, finite size scaling of known dopant levels shows how to treat the band gap problem: in < or = 200 atom supercells with no corrections, continuing to consider levels into the theoretical conductin band (extended gap) comes closest to experiment. However, for larger cells or when supercell approximation errors are removed, a scissors scheme stretching the theoretical band gap onto the experimental one is in fact correct.
42.	Chung, Sunjae, et al. (författare) Spin transfer torque generated magnetic droplet solitons (invited) 2014 Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 115:17 Tidskriftsartikel (refereegranskat)abstract We present recent experimental and numerical advancements in the understanding of spin transfer torque generated magnetic droplet solitons. The experimental work focuses on nano-contact spin torque oscillators (NC-STOs) based on orthogonal (pseudo) spin valves where the Co fixed layer has an easy-plane anisotropy, and the [Co/Ni] free layer has a strong perpendicular magnetic anisotropy. The NC-STO resistance and microwave signal generation are measured simultaneously as a function of drive current and applied perpendicular magnetic field. Both exhibit dramatic transitions at a certain current dependent critical field value, where the microwave frequency drops 10 GHz, modulation sidebands appear, and the resistance exhibits a jump, while the magnetoresistance changes sign. We interpret these observations as the nucleation of a magnetic droplet soliton with a large fraction of its magnetization processing with an angle greater than 90 degrees, i.e., around a direction opposite that of the applied field. This interpretation is corroborated by numerical simulations. When the field is further increased, we find that the droplet eventually collapses under the pressure from the Zeeman energy. (C) 2014 AIP Publishing LLC.
43.	G.E. Grechnev,, et al. (författare) Electronic structure and magnetic properties of Lithium manganese spinels 2003 Ingår i: J.Magn. Magn. Matt.. ; 258, s. 287-289 Tidskriftsartikel (refereegranskat)abstract Electronic and magnetic structures of the spinel-type lithium–manganese oxides LixMn2O4, x=0,0.5,1, are studied ab initio by employing a full-potential LMTO method. The effect of the orthorhombic distortion on electronic structure and magnetism of LiMn2O4 was investigated, and our calculations do not show a substantial charge ordering at the structural transition from the cubic spinel to the orthorhombic structure.
44.	Gavrylyuk, O. O., et al. (författare) Influence of laser annealing on SiOx films properties 2015 Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332. ; 336, s. 217-221 Tidskriftsartikel (refereegranskat)abstract The interaction of laser irradiation with SiOx films, and the process of decomposition of SiOx on SiO2 and Si nanocrystals under the influence of laser irradiation are investigated. The mathematical modeling of temperature distribution in a c-Si wafer as well as on its surface is carried out. It is shown that laser pulses can efficiently heat up the samples of crystalline silicon. Using multi-pulse procedure, the temperature necessary for annealing can be achieved with lower intensity of laser irradiation. Experimental investigations of laser-annealed SiOx films allowed determining their transformation with the formation of nanoislands. It was concluded that the surface topology, dielectric matrix structure, and electrical conductivity depend on laser beam intensity during the annealing process.
45.	Heyl, M., et al. (författare) Dynamical topological quantum phase transitions for mixed states 2017 Ingår i: Physical Review B. - 2469-9950. ; 96:18 Tidskriftsartikel (refereegranskat)abstract We introduce and study the dynamical probes of band-structure topology in the postquench time evolution of quantum many-body systems initialized in mixed states. Our construction generalizes the notion of dynamical quantum phase transitions (DQPTs), a real-time counterpart of conventional equilibrium phase transitions in quantum dynamics, to finite temperatures and generalized Gibbs ensembles. The nonanalytical signatures hallmarking these mixed-state DQPTs are found to be characterized by observable phase singularities manifesting in the dynamical formation of vortex-antivortex pairs in the interferometric phase of the density matrix. Studying quenches in Chern insulators, we find that changes in the topological properties of the Hamiltonian can be identified in this scenario, without ever preparing a topologically nontrivial or low-temperature initial state. Our observations are of immediate relevance for current experiments aimed at realizing topological phases in ultracold atomic gases.
46.	Hunter Dunn, Jonathan, et al. (författare) Vanishing Magnetic Interactions in Ferromagnetic Thin Films 2005 Ingår i: PHYSICAL REVIEW LETTERS. - : American Physical Society (APS). - 0031-9007 .- 1079-7114. ; 94:21, s. 217202- Tidskriftsartikel (refereegranskat)abstract We have used element-specific hysteresis measurements, based on the x-ray magnetic circular dichroism technique, to investigate magnetic trilayer structures composed of Fe and Ni layers. Within a critical regime we have discovered a class of structures in which the exchange interaction, the mechanism responsible for the macroscopic magnetism, can become vanishingly small. The experimental observations are supported by first principles theory and are explained as arising from a cancellation of several competing magnetic interactions. Hence, we have discovered a system with a novel exchange interaction between magnetic layers in direct contact that replaces the conventional exchange interaction in ferromagnets.
47.	Joyce, J.J., et al. (författare) Photoemission and the electronic structure of PuGaCo$_5$ 2003 Ingår i: Physical Review Letters. ; 91, s. 176401- Tidskriftsartikel (refereegranskat)abstract The electronic structure of the first Pu-based superconductor PuCoGa5 is explored using photoelectron spectroscopy and a novel theoretical scheme. Exceptional agreement between calculation and experiment defines a path forward for understanding the electronic structure aspects of Pu-based materials. The photoemission results show two separate regions of 5f electron spectral intensity, one at the Fermi energy and another centered 1.2 eV below the Fermi level. The results for PuCoGa5 clearly indicate 5f electron behavior on the threshold between localized and itinerant. Comparisons to delta phase Pu metal show a broader framework for understanding the fundamental electronic properties of the Pu 5f levels in general within two configurations, one localized and one itinerant.
48.	Kadas, Krisztina, et al. (författare) Thermo-physical properties of body-centered cubic iron-magnesium alloys under extreme conditions 2011 Ingår i: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 151:3, s. 203-207 Tidskriftsartikel (refereegranskat)abstract Using density functional theory formulated within the framework of the exact muffin-tin orbitals method, we investigate the thermo-physical properties of body-centered cubic (bcc) iron-magnesium alloys, containing 5 and 10 atomic % Mg, under extreme conditions, at high pressure and high temperature. The temperature effect is taken into account via the Fermi-Dirac distribution of the electrons. We find that at high pressures pure bcc iron is dynamically unstable at any temperature, having a negative tetragonal shear modulus (C'). Magnesium alloying significantly increases C' of Fe, and bcc Fe-Mg alloys become dynamically stable at high temperature. The electronic structure origin of the stabilization effect of Mg is discussed in detail. We show that the thermo-physical properties of a bcc Fe-Mg alloy with 5% Mg agree well with those of the Earth's inner core as provided by seismic observations. (C) 2010 Elsevier Ltd. All rights reserved.
49.	Kuzmin, M., et al. (författare) Atomic structure of Yb/Si(100)(2X6) : Interrelation between the silicon dimer arrangement and Si 2p photoemission line shape 2010 Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 82:11, s. 113302- Tidskriftsartikel (refereegranskat)abstract Combining photoelectron spectroscopy and density-functional theory calculations, we have studied the atomic geometry of Yb/Si(100)(2 X 6) reconstruction and the mechanisms responsible for its stabilization as well as the influence of this reconstruction on Si 2p core-level photoemission. The analysis of measured and calculated surface core-level shifts supports the recently proposed model of the Yb/Si(100)(2 X 6). It involves, in agreement with valence-band measurements, unbuckled (symmetrical) silicon dimers, leading to unusually narrowed Si 2p line shape as compared to those of related systems. The origin of the symmetrical dimers in the (2 X 6) structure is discussed in the context of previous results in literature.
50.	Kuzmin, M., et al. (författare) Surface core-level shifts on Ge(111)c(2 x 8) : Experiment and theory 2011 Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 83:24, s. 245319- Tidskriftsartikel (refereegranskat)abstract Combining high-resolution photoelectron spectroscopy and density functional theory (DFT) calculations, 3d photoemission line shape and surface core-level shifts have been reinvestigated on the Ge(111)c(2 x 8) surface. It is found that 3d spectra include, in addition to the bulk and three surface-shifted components reported in literature, a component that was not identified in earlier measurements with a lower resolution. The detailed interpretation of these spectra and their line shape is made on the basis of DFT calculations. It is shown that the lowest binding energy component is due to the rest atoms. The higher binding energy emission is caused by the adatoms and the third-layer atoms that are below the adatoms. Finally, the two other surface components originate from the first- and second-layer atoms. The screening effects in the Ge(111)c(2 x 8) are discussed.

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