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Long-lived electron emission reveals localized plasmon modes in disordered nanosponge antennas

Light(Science & Applications) 2017年第1期6卷 458-465页

作者： Germann Hergert Jan Vogelsang felix Schwarz Dong Wang Heiko Kollmann Petra Groß Christoph Lienau Erich runge Peter Schaaf Carl von Ossietzky Universität Institut für PhysikCenter of Interface ScienceD-26129 OldenburgNiedersachsenGermany Technische Universität Ilmenau Institut für Physik and Institut für Mikro-und Nanotechnologien MacroNano®D-98693 IlmenauThüringenGermany Technische Universität Ilmenau Institut für Mikro-und Nanotechnologien MacroNano®and Institut für WerkstofftechnikFachgebiet Werkstoffe der ElektrotechnikD-98693 IlmenauThüringenGermany forschungszentrum Neurosensorik Carl von Ossietzky UniversitätD-26111 OldenburgNiedersachsenGermany

We report long-lived,highly spatially localized plasmon states on the surface of nanoporous gold nanoparticles—nanosponges—with high excitation *** is well known that disorder on the nanometer scale,particularly in two-dimensional systems,can lead to plasmon localization and large field enhancements,which can,in turn,be used to enhance nonlinear optical effects and to study and exploit quantum optical ***,we introduce promising,three-dimensional model systems for light capture and plasmon localization as gold nanosponges that are formed by the dewetting of gold/silver bilayers and *** study light-induced electron emission from single nanosponges,a nonlinear process with exponents of n≈5...7,using ultrashort laser pulse excitation to achieve femtosecond time *** long-lived electron emission process proves,in combination with optical extinction measurements and finite-difference time-domain calculations,the existence of localized modes with lifetimes of more than 20 *** electrons couple efficiently to the dipole antenna mode of each individual nanosponge,which in turn couples to the ***,individual gold nanosponges are cheap and robust disordered nanoantennas with strong local resonances,and an ensemble of nanosponges constitutes a meta material with a strong polarization independent,nonlinear response over a wide frequency range.

关键词： disorder-induced plasmon localization nanoantennas nanoporous gold nanoparticles ultrafast photoemission spectroscopy

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Dust growth in protoplanetary disks-a comprehensive experimental / theoretical approach

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research in Astronomy and Astrophysics 2010年第12期10卷 1199-1214页

作者： Jürgen Blum institut für Geophysik und extraterrestrische physik University of Braunschweig

More than a decade of dedicated experimental work on the collisional physics of protoplanetary dust has brought us to a point at which the growth of dust aggregates can - for the first time - be self-consistently and reliably modeled. In this article, the emergent collision model for protoplanetery dust aggregates, as well as the numerical model for the evolution of dust aggregates in protoplanetary disks, is reviewed. It turns out that, after a brief period of rapid collisional growth of fluffy dust aggregates to sizes of a few centimeters, the protoplanetary dust particles are subject to bouncing collisions, in which their porosity is considerably decreased. The model results also show that low-velocity fragmentation can reduce the final mass of the dust aggregates but that it does not trigger a new growth mode as discussed previously. According to the current stage of our model, the direct formation of kilometer-sized planetesimals by collisional sticking seems unlikely, implying that collective effects, such as the streaming instability and the gravitational instability in dust-enhanced regions of the protoplanetary disk, are the best candidates for the processes leading to planetesimals.

关键词： planetary systems: protoplanetary disks -- planetary systems: formation-- methods: laboratory -- methods: numerical

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Quantum Impurity Models with Coupled Cluster Method

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Communications in Theoretical Physics 2010年第9期54卷 509-517页

作者： Clive Emary Tobias Brandes institut für Theoretische physik

We investigate the ground-state properties of the Anderson single impurity model （finite Coulomb impurity repulsion） with the Coupled Cluster Method. We consider different CCM reference states and approximation schemes and make comparison with exact Green＇s function results for the non-interacting model and with Brillouin-Wigner perturbation theory for the full interacting model. Our results show that coupled cluster techniques are well suited to quantum impurity problems.

关键词： strongly correlated electrons Anderson model coupled-cluster method quantum impurity

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recent results from NA48/2

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Chinese Physics C 2010年第6期34卷 749-752页

作者： Cristina Morales Morales institut für physik Universitt Mainz

recent results on radiative K^± decays from the NA48/2 experiment are reported. from the full NA48/2 data set, about a million K^±→π^±π^γ decays were reconstructed. Based on this sample, the first measurement of the interference between direct photon emission and inner bremsstrahlung in K^±→π^±π^γ decays was performed. Stringent limits on CP violation in this decay were also set. In addition, a precise measurement of the branching fraction of K^±→π^±γγ is presented. This measurement was based on a data sample of more than 1000 event candidates. Also the related decay K^±→π^±e^＋e^-γ has first been observed. results of the measurement of the decay rate and the decay parameter 5 are summarized.

关键词： radiative K^± decays NA48/2 CP violation

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Observing charge separation in nanoantennas via ultrafast point-projection electron microscopy

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Light(Science & Applications) 2018年第1期7卷 532-539页

作者： Jan Vogelsang Germann Hergert Dong Wang Petra Groß Christoph Lienau Carl von Ossietzky Universität Institut für Physik and Center of Interface Science26129 OldenburgNiedersachsenGermany TU Ilmenau Institut für Werkstofftechnik und Institut für Mikro-und Nanotechnologien98693 IlmenauThüringenGermany Carl von Ossietzky Universität Forschungszentrum Neurosensorik26129 OldenburgNiedersachsenGermany Department of Physics Lund UniversityBox 11822100 LundSweden

Observing the motion of electrons on their natural nanometer length and femtosecond time scales is a fundamental goal of and an open challenge for contemporary ultrafast science1–*** present,optical techniques and electron microscopy mostly provide either ultrahigh temporal or spatial resolution,and microscopy techniques with combined space-time resolution require further development6–*** this study,we create an ultrafast electron source via plasmon nanofocusing on a sharp gold taper and implement this source in an ultrafast point-projection electron *** source is used in an optical pump—electron probe experiment to study ultrafast photoemissions from a nanometer-sized plasmonic antenna12–*** probe the real space motion of the photoemitted electrons with a 20-nm spatial resolution and a 25-fs time resolution and reveal the deflection of probe electrons by residual holes in the *** is a step toward time-resolved microscopy of electronic motion in nanostructures.

关键词： projection separation sized

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Growth of Large-Area Single- and Bi-Layer Graphene by Controlled Carbon Precipitation on Polycrystalline Ni Surfaces

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Nano research 2009年第6期2卷 509-516页

作者： Alfonso reina Stefan Thiele Xiaoting Jia Sreekar Bhaviripudi Mildred S.Dresselhaus Juergen A.Schaefer Jing Kong Department of Materials Science and Engineering Massachusetts Institute of TechnologyCambridgeMassachusetts 02139USA institut für physik and institut für mikro-und nanotechnologien Technische Universität IlmenauIlmenau 98684Germany Department of Electrical Engineering and Computer Science Massachusetts Institute of TechnologyCambridgeMassachusetts 02139USA Department of Physics Massachusetts Institute of TechnologyCambridgeMassachusetts 02139USA

We report graphene films composed mostly of one or two layers of graphene grown by controlled carbon precipitation on the surface of polycrystalline Ni thin films during atmospheric chemical vapor deposition(CVD).Controlling both the methane concentration during CVD and the substrate cooling rate during graphene growth can signifi cantly improve the thickness *** a result,one-or two-layer graphene regions occupy up to 87%of the fi lm *** layer coverage accounts for 5%11%of the overall fi *** regions expand across multiple grain boundaries of the underlying polycrystalline Ni fi *** number density of sites with multilayer graphene/graphite(>2 layers)is reduced as the cooling rate *** fi lms can also be transferred to other substrates and their sizes are only limited by the sizes of the Ni fi lm and the CVD ***,we demonstrate the formation of fi lms as large as 1 in^(2).These fi ndings represent an important step towards the fabrication of large-scale high-quality graphene samples.

关键词： Graphene chemical vapor deposition nickel catalyst carbon nanomaterials

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The atomic structure and the properties of Ununbium (Z=112) and Mercury (Z=80)

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Science China(Physics,Mechanics & Astronomy) 2007年第6期50卷 707-715页

作者： S.frITZSCHE B.frICKE institut fr physik Universita..t Kassel 34132Germany

A super heavy element Uub (z = 112) has been studied theoretically in conjunction with rela-tivistic effects and the effects of electron *** atomic structure and the oscillator strengths of low-lying levels have been calculated,and the ground states have also been determined for the singly and doubly charged ions. The influence of relativity and correlation effects to the atomic properties of such a super heavy element has been investigated in detail. The results have been compared with the properties of an element Hg. Two energy levels at wave numbers 64470 and 94392 are suggested to be of good candidates for experimental observations.

关键词： super heavy element atomic structure relativistic effects electron correlation effects MCDf method

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Statistical learning of engineered topological phases in the kagome superlattice of AV_(3)Sb_(5)

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npj Computational Materials 2022年第1期8卷 624-629页

作者： Thomas Mertz Paul Wunderlich Shinibali Bhattacharyya francesco ferrari roser Valentí institut für Theoretische physik Goethe-UniversitätFrankfurt am MainGermany

recent experimental findings have reported the presence of unconventional charge orders in the enlarged(2×2)unit-cell of kagome metals AV3Sb5(A=K,rb,Cs)and hinted towards specific topological *** by these discoveries,we investigate the types of topological phases that can be realized in such kagome *** this context,we employ a recently introduced statistical method capable of constructing topological models for any generic *** analyzing large data sets generated from symmetry-guided distributions of randomized tight-binding parameters,and labeled with the corresponding topological index,we extract physically meaningful *** illustrate the possible real-space manifestations of charge and bond modulations and associated flux patterns for different topological classes,and discuss their relation to present theoretical predictions and experimental signatures for the AV_(3)Sb_(5)***,we predict higher-order topological phases that may be realized by appropriately manipulating the currently known systems.

关键词： topological signature meaningful

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Hunting η-bound nuclei

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Chinese Physics C 2010年第9期34卷 1218-1223页

作者： H.Machner institut für Kernphysik Forschungszentrum Jülich fakultt für physik Universitt Duisburg-Essen

The η meson can be bound to atomic *** search is discussed in the form of final state interaction for the reactions dp → 3 Heη and dd → 4 Heη.for the latter case tensor polarized deuterons were used in order to extract the s-wave *** both reactions complex scattering lengths are deduced： a 3 Heη = ± 10.7±0.8 ＋0.1 -0.5 ＋i· 1.5±2.6 ＋1.0-0.9 fm and a 4 Heη = [±（3.1±0.5）＋i·（0±0.5）] *** a two-nucleon transfer reaction under quasi-free conditions,p^ 27 Al → ^3 HeX,was *** system X can be the bound 25 Mg  η at *** a possible decay of an intermediate N  （1535） is required,a highly significant bump shows up in the missing mass *** data give for a bound state a binding energy of 13.3±1.6 MeV and a width of σ=4.4±1.3 MeV.

关键词： η meson production η nucleus interaction final state interaction recoil free kinematics

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Limits on light emission from silicon

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Chinese Optics Letters 2009年第4期7卷 268-270页

作者： Peter Würfel institut für Angewandte physik Universitt KarlsruheD-76128 KarlsruheGermany

Although silicon is an indirect semiconductor, light emission from silicon is governed by the same gener- alized Planck＇s radiation law as the emission from direct semiconductors. The emission intensity is given by the absorptance of the volume in which there is a difference of the quasi fermi energies. A difference of the fermi energies may result h＇om the absorption of external light （photoluminescence） or from the injection of electrons and holes via selective contacts （electroluminescence）. The quantum efficiency may be larger than 0.5 for carrier densities below 10^15 cm^-3. At larger densities, non-radiative recombination, in particular Auger recombination dominates. At all carrier densities, the relation between emission intensity and difference of the quasi fermi energies is maintained. Since this difference is equal to the voltage of a properly designed solar cell, luminescence is the key indicator of material quality for solar cells.

关键词： Carrier concentration fermi level Light Light emission Photoluminescence Semiconducting silicon Silicon

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