Abstract
Charge acceleration during an intense light field application to solids attracts much attention as elementary processes in high-harmonic generation and photoelectron emission. For ...manipulating such attosecond dynamics of charge, carrier-envelope-phase (CEP: relative phase between carrier oscillation of light field and its envelope function) control has been employed in insulators, nanometal and graphene. In superconducting materials, collective control of charge motion is expected because of its strongly coherent nature of quasi-particles. Here we report that, in a layered organic superconductor, a non-linear petahertz current driven by a single-cycle 6 femtosecond near infrared field shows up as second harmonic generation (SHG), which is in contrast to the common belief that even harmonics are forbidden in the centrosymmetric system. The SHG represents a CEP sensitive nature and an enhancement near the superconducting temperature. The result and its quantum many-body analysis indicate that a polarized current is induced by non-linear acceleration of charge, which is amplified by superconducting fluctuations. This will lead to petahertz functions of superconductors and of strongly correlated systems.
Application of an intense light field to solids produces enormous and ultrafast nonlinear phenomena such as high-harmonic generation1,2 and attosecond charge dynamics3,4. These are distinct from ...conventional photonics. However, the main targets for investigation have been limited to insulators and semiconductors, although theoretical approaches have also been developed for correlated metals and superconductors5. Here, in a layered organic superconductor, a nonlinear charge oscillation driven by a nearly single-cycle strong electric field of >10 MV cm−1 is observed as a stimulated emission. The charge oscillation is different from a linear response and ascribed to a polar charge oscillation with a period of ∼6 fs. This nonlinear polar charge oscillation is enhanced by critical fluctuations near a superconducting transition temperature and a critical end-point of first-order Mott transitions. Its observation on an ultrafast timescale of ∼10 fs clarifies that Coulomb repulsion plays an essential role in the superconductivity of organic superconductors.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, SBMB, UL, UM, UPUK
Leukoencephalopathies encompass all clinical syndromes that predominantly affect brain white matter. Genetic diagnosis informs clinical management of these patients, but a large part of the genetic ...contribution to adult leukoencephalopathy remains unresolved. To examine this genetic contribution, we analyzed genomic DNA from 60 Japanese patients with adult leukoencephalopathy of unknown cause by next generation sequencing using a custom‐designed gene panel. We selected 55 leukoencephalopathy‐related genes for the gene panel. We identified pathogenic mutations in 8 of the 60 adult leukoencephalopathy patients (13.3%): NOTCH3 mutations were detected in 5 patients, and EIF2B2, CSF1R, and POLR3A mutations were found independently in 1 patient each. These results indicate that cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) caused by NOTCH3 mutations is the most frequent adult leukoencephalopathy in our cohort. Moreover, brain imaging analysis indicates that CADASIL patients who do not present typical phenotypes may be underdiagnosed if not examined genetically.
About 13.3% of adult patients with leukoencephalopathy were definitively disgnosed with known, apparently pathological or novel mutations.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
This study describes a multifunctional envelope-type nano device (MEND) that mimics an envelope-type virus based on a novel packaging strategy. MEND particles contain a DNA core packaged into a lipid ...envelope modified with an octaarginine peptide. The peptide mediates internalization via macropinocytosis, which avoids lysosomal degradation. MEND-mediated transfection of a luciferase expression plasmid achieved comparable efficiency to adenovirus-mediated transfection, with lower associated cytotoxicity. Furthermore, topical application of MEND particles containing constitutively active bone morphogenetic protein (BMP) type IA receptor (caBmpr1a) gene had a significant impact on hair growth in vivo. These data demonstrate that MEND is a promising non-viral gene delivery system that may provide superior results to existing non-viral gene delivery technologies.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We demonstrate the ultrafast photoinduced Mott transition from a charge transfer insulator to a metal in a halogen-bridged Ni-chain compound by pump-probe reflection spectroscopy. Upon the ...irradiation of a 130-femtosecond laser pulse, the spectral weight of the gap transition is transferred to the inner-gap region. When the photoexcitation density exceeds 0.1/Ni site, the Drude-like high-reflection band appears in the infrared region, signaling the formation of a metallic state. The photogeneration of the metallic state and the subsequent recovery to the original gapped state occur within a few picoseconds.
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Rapid polarization control by an electric field in ferroelectrics is important to realize high-frequency modulation of light, which has potential applications in optical communications. To achieve ...this, a key strategy is to use an electronic part of ferroelectric polarization. A hydrogen-bonded molecular ferroelectric, croconic acid, is a good candidate, since π-electron polarization within each molecule is theoretically predicted to play a significant role in the ferroelectric-state formation, as well as the proton displacements. Here, we show that a sub-picosecond polarization modulation is possible in croconic acid using a terahertz pulse. The terahertz-pulse-pump second-harmonic-generation-probe and optical-reflectivity-probe spectroscopy reveal that the amplitude of polarization modulation reaches 10% via the electric-field-induced modifications of π-electron wavefunctions. Moreover, the measurement of electric-field-induced changes in the infrared molecular vibrational spectrum elucidates that the contribution of proton displacements to the polarization modulation is negligibly small. These results demonstrate the electronic nature of polarization in hydrogen-bonded molecular ferroelectrics. The ultrafast polarization control via π-electron systems observed in croconic acid is expected to be possible in many other hydrogen-bonded molecular ferroelectrics and utilized for future high-speed optical-modulation devices.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The realization of all-optical switching, modulating and computing devices
is an important goal in modern optical technology. Nonlinear optical materials
with large third-order nonlinear ...susceptibilities (χ(3))
are indispensable for such devices, because the magnitude of this quantity
dominates the device performance. A key strategy in the development of new
materials with large nonlinear susceptibilities is the exploration of quasi-one-dimensional
systems, or 'quantum wires'-the quantum
confinement of electron-hole motion in one-dimensional space can enhance χ
(3). Two types of chemically synthesized quantum wires have been extensively
studied: the band insulators of silicon polymers, and Peierls insulators of π-conjugated
polymers and platinum halides. In these systems, χ(3) values
of 10-12 to 10-7 e.s.u. (electrostatic system
of units) have been reported. Here we demonstrate
an anomalous enhancement of the third-order nonlinear susceptibility in a
different category of quantum wires: one-dimensional Mott insulators of 3
d transition-metal oxides and halides. By analysing the electroreflectance
spectra of these compounds, we measure χ(3) values in the
range 10-8 to 10-5 e.s.u. The anomalous enhancement
results from a large dipole moment between the lowest two excited states of
these systems.
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DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Ultrafast photoinduced phase transition in a spin-Peierls (SP) system of K-tetracyanoquinodimethane (K-TCNQ) was studied by femtosecond (fs) reflection spectroscopy. Photocarriers destabilize the SP ...phase, resulting in a decrease in molecular dimerization within 400 fs. Such a melting of the SP phase drives three kinds of coherent oscillations. By comparing the oscillations with the Raman bands activated by the dimerization, we show that the oscillation of 20 cm-1 is due to an LO phonon, and it plays an important role for the stabilization of the SP phase.
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We have observed the characteristic temperature dependence of the intermolecular phonon spectrum in the organic dimer Mott insulator Kappa -(ET) sub(2) Cu sub(2) (CN) sub(3) exhibiting a dielectric ...anomaly at ~30 K. The anomalous spectral narrowing of the 55 cm super(-1) phonon peak at ~30 K was analyzed in terms of motional narrowing within the framework of a stationary Gaussian process, i.e., the phonon frequency is modulated by the ultrafast charge fluctuation. The spectral narrowing occurs because the time constant of the correlation time tauc and the amplitude Delta of the frequency modulation satisfy the relation tauc < 1/ Delta at 30 K. At temperatures below 30 K, the motional narrowing is disturbed by the increase of tauc, near the charge-glass or the short-range order at 6 K. On the other hand, for temperatures above 30 K, the motional narrowing is disturbed by the increase of Delta with increasing temperature.
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