170,413 research outputs found
Electrons catch a terahertz wave: Far-infrared fi elds control ultrashort electron pulses
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Data for: Ultrafast nanoimaging of the order parameter in a structural phase transition
No full textThis dataset contains the data displayed in the publication "Ultrafast nanoimaging of the order parameter in a structural phase transition" by Th. Danz, T. Domröse, and C. Ropers
Femtosecond trimer quench in the unconventional charge-density-wave material 1 T ′ − TaTe 2
Full text linkUltrafast optical switching of materials properties promises future technological applications, enabled by fundamental insights about microscopic couplings and nonequilibrium phenomena. Transition-metal dichalcogenides (TMDCs) combine photosensitivity with strong correlations, furthering rich phase diagrams and enhanced tunability. The compound 1 T ′ − TaTe 2 exhibits an electronically and structurally unique set of charge density waves (CDWs), featuring an unusual increase in conductivity and amplitude modes of low prominence. Compared to other charge-ordered TMDCs, only very few studies addressed the ultrafast response of this material to optical excitation. In particular, the question whether such unconventional properties translate to unusual quench dynamics remains largely unresolved. Here, we investigate the structural dynamics in 1 T ′ − TaTe 2 by means of ultrafast nanobeam electron diffraction at an unprecedented repetition rate of 2 MHz . We reveal a strongly directional cooperative atomic motion during the one-dimensional quench of the low-temperature trimer lattice. These dynamics are completed within less than 500 fs , substantially faster than reported previously. In striking contrast, the periodic lattice distortion of the room-temperature phase is unusually robust against high-density electronic excitation. In conjunction with the known sensitivity of 1 T ′ − TaTe 2 to chemical doping, we thus expect the material to serve as a versatile platform for tunable structural control by optical stimuli. Published by the American Physical Society 2024Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/50110000165
Childhood-onset generalized epilepsy in Bainbridge-Ropers syndrome
Full text linkBainbridge-Ropers syndrome is a genetic syndrome caused by heterozygous loss-of-function pathogenic variants in ASXL3, which encodes a protein involved in transcriptional regulation. Affected individuals have multiple abnormalities including developmental impairment, hypotonia and characteristic facial features. Seizures are reported in approximately a third of cases; however, the epileptology has not been thoroughly studied. We identified three patients with pathogenic ASXL3 variants and seizures at Austin Health and in the DECIPHER database. These three patients had novel de novo ASXL3 pathogenic variants, two with truncation variants and one with a splice site variant. All three had childhood-onset generalized epilepsy with generalized tonic-clonic seizures, with one also having atypical absence seizures. We also reviewed available clinical data on five published patients with Bainbridge-Ropers syndrome and seizures. Of the five previously published patients, three also had generalized tonic-clonic seizures, one of whom also had possible absence seizures; a fourth patient had absence seizures and possible focal seizures. EEG typically showed features consistent with generalized epilepsy including generalized spike-wave, photoparoxysmal response, and occipital intermittent rhythmic epileptiform activity. Bainbridge-Ropers syndrome is associated with childhood-onset generalized epilepsy with generalized tonic-clonic seizures and/or atypical absence seizures.</p
Resonant excitation and all-optical switching of femtosecond soliton molecules
Full text linkThe emergence of confined structures and pattern formation are exceptional manifestations of nonlinear interactions found in a variety of physical, chemical and biological systems. Facilitated by optical nonlinearities, solitons enable ultrashort temporal confinement of light and stable propagation despite the presence of dispersion. Such particle-like structures can assemble in stable arrangements, forming ‘soliton molecules’. Recent work has revealed oscillatory internal motions of these bound states, akin to molecular vibrations raising the question of how far the ‘molecular’ analogy reaches, that is, whether further concepts from molecular spectroscopy apply and whether such intramolecular dynamics can be externally driven or manipulated. Here, we probe and control ultrashort bound states in an optical oscillator, using real-time spectral interferometry and time-dependent excitation. For a frequency-swept pump modulation, we analyse the nonlinear response and resolve anharmonicities in soliton interactions that lead to generation of overtones and sub-harmonics. Applying stronger stimuli, we demonstrate all-optical switching between states with different binding separations. These results could be applied to rapid pulse-pair generation and may stimulate the development of future instruments for ultrafast science
Tailored high-contrast attosecond electron pulses for coherent excitation and scattering
Full text linkTemporally shaping the density of electron beams using light forms the basis for a wide range of established and emerging technologies, including free-electron lasers and attosecond electron microscopy. The modulation depth of compressed electron pulses is a key figure of merit limiting applications. In this work, we present an approach for generating background-free attosecond electron pulse trains by sequential inelastic electron-light scattering. Harnessing quantum interference in the fractional Talbot effect, we suppress unwanted background density in electron compression by several orders of magnitude. Our results will greatly enhance applications of coherent electron-light scattering, such as stimulated cathodoluminescence and streaking
Theory of electron energy loss near plasmonic wires, nanorods, and cones
No full textWe present an analytical description of the electron energy loss near plasmonic nanostructures with cylindrical symmetry as a three-step process: (i) electron-induced excitation of surface plasmon modes, (ii) their propagation and reflection, and (iii) the backaction on the electrons. The model incorporates relativistic effects, retardation, and light emission, and can treat arbitrary tilted electron trajectories. Convincing agreement with recent experimental data is demonstrated
Ultra-fast nano-optics
No full textUltra-last nano-optics is a comparatively young and rapidly growing field of research aiming at probing, manipulating and controlling ultrafast optical excitations oil nanometer length scales. This ability to control light on nanometric length and femtosecond time scales Opens Lip exciting possibilities for probing dynamic processes in nanostructures in real time and space. This article gives a brief introduction into the emerging research field of ultrafast nano-optics and discusses recent progress made in it. A particular emphasis is laid oil the recent experimental work performed in the authors' laboratories. We specifically discuss how ultrafast nano-optical techniques can be used to probe and manipulate coherent optical excitations in individual I and dipole-coupled pairs Of quantum dots, probe the dynamics of surface plasmon polariton excitations in metallic nanostructures, generate novel nanometer-sized ultrafast light and electron sources and reveal the dipole interaction between excitons and surface plasmon polaritons in hybrid metal-semiconductor nanostructures. Our results indicate that Such hybrid nanostructures carry significant potential for realizing novel nano-optical devices such as ultrafast nano-optical switches as well as surface plasmon polariton amplifiers and lasers. [GRAPHICS] Two-dimensional finite difference time domain (FDTD) simulation of the spatio-temporal evolution of a 10 fs light pulse at a center wavelength of 810 nm propagating through a tapered, perfectly conducting metal-coated fiber probe of 100 nm aperture diameter. The field intensity vertical bar E-x(x,y,t)vertical bar(2) is displayed oil a logarithmic intensity scale at four different instants in time. After t similar to 14 fs the pulse center reaches the aperture, generating directly below it an ultra-short near-field spot of light. (C) 2009 by WILEY-VCH Verlag GmbH & Co. KGaA. Weinhei
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