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Photoexcitation in solids brings about transitions of electrons/holes between different electronic bands. If the solid lacks an inversion symmetry, these electronic transitions support spontaneous photocurrent due to the geometric phase of the constituting electronic bands: the Berry connection. This photocurrent, termed shift current, is expected to emerge on the timescale of primary photoexcitation process. We observe ultrafast evolution of the shift current in a prototypical ferroelectric semiconductor antimony sulfur iodide (SbSI) by detecting emitted terahertz electromagnetic waves. By sweeping the excitation photon energy across the bandgap, ultrafast electron dynamics as a source of terahertz emission abruptly changes its nature, reflecting a contribution of Berry connection on interband optical transition. The shift excitation carries a net charge flow and is followed by a swing over of the electron cloud on a subpicosecond timescale. Understanding these substantive characters of the shift current with the help of first-principles calculation will pave the way for its application to ultrafast sensors and solar cells.

We present full (3+1 )D dynamical simulations to study collective behavior in ultra-peripheral nucleus-nucleus collisions (UPC) at the Large Hadron Collider (LHC) with the 3DGlauber+MUSIC+UrQMD framework [1, 2]. By extrapolating from asymmetric p+Pb collisions, we simulate a quasi-real photon γ* interacting with the Pb nucleus in an ultra-peripheral collision at the LHC, assuming strong final-state effects. We study the elliptic flow hierarchy between p+Pb and γ*+Pb collisions, which is dominated by the difference in longitudinal flow decorrelations. Our theoretical framework provides a quantitative tool to study collectivity in small asymmetric collision systems at current and future collider experiments.

Lakes play a crucial role in the continental carbon cycle by burying large amounts of terrestrial organic matter (OM) in their sediments. Recent increases in carbon accumulation rates (CAR) have been linked to anthropogenic climate and land-use changes. However, the extent to which modern CAR exceeds naturally varying Holocene trends remains unclear because of a lack of datasets combining long-term and recent CAR records with consistent sediment properties across broad spatial scales. Here, we quantify temporal change in CAR from the pre-modern Holocene (11 000 BCE-1850 CE) to the industrial era (post-1850) across boreal and temperate lakes using a novel bulk density (%OM) model. Our model improves predictive accuracy ( R 2 = 0.96) compared to previous approaches and captures variability across a wide range of OM, ranging from 1.1% to 94%. CAR values and variance were lower across cores pre-1850 (14.8 ± 9.3 g C m −2 yr −1 ), whereas post-1850 values were on average 34.6 ± 23.4 g C m −2 yr −1 . Moreover, CAR variation from date to date within cores remained low and stable pre-1850 and tended to deviate positively from zero post-1850 (∼12% ± 18% above baseline), denoting CAR acceleration. However, nearly one-third of post-1850 layers decreased, highlighting enhanced variability in recent observations. The strongest increases occurred in northern, low-elevation lakes with low pre-1850 CAR. Overall, our results suggest that post-industrial human activities have pushed lake carbon burial beyond Holocene baselines, increasing accumulation rates and variability both within and across sediment cores. This shows that anthropogenic influence has reshaped carbon storage in inland waters, with implications for predicting future carbon dynamics.

Abstract Nuclear magnetic moment (μ) measurements provide useful information on nuclear structures. For unstable nuclei, nuclear magnetic resonance (NMR) of in-beam polarized nuclei with beta asymmetry detection (β-NMR) is a powerful method to determine μ. In this method, the sign of μ can be determined using rotating radio-frequency (RF) fields. In this article, we developed a new system to apply rotating RF fields that can produce almost complete circular rotation, compared to that in previous systems. Using this system, we successfully determined the sign of μ for 29P and 25Al. For both nuclei, the sign of μ is positive, which is consistent with the predictions of the single particle shell model. This article details the new rotating RF field system.

Abstract The proton-induced deuteron knockout reaction $(p,pd)$ provides a unique opportunity to exploit proton–neutron correlations and the deuteron cluster structure of nuclei. Direct deuteron knockout experiments on $^{12}$C and $^{16}$O under quasi-free scattering conditions have been carried out under the ONOKORO project using a 226-MeV proton beam at the Research Center for Nuclear Physics, Osaka, Japan. Deuterons from the knockout reaction, acting as clusters, were unambiguously detected at the focal plane of the Large Acceptance Spectrometer. Outgoing protons, following the knockout of clusters, were detected at the focal plane of the Grand Raiden spectrometer to correctly reconstruct the expected events. $(p,pd)$ reactions are established successfully, and excitation energy spectra for the residual nuclei $^{10}$B and $^{14}$N are obtained. Results showed that a large difference in transition strength toward the low-lying energy level of residual nuclei, including the ground state, was found in comparison to other studies. Theoretical calculations using the Proton-Induced KnockOut reaction calculation for Exclusive processes (PIKOE) package based on the distorted-wave impulse approximation are conducted to deduce the triple differential cross section of the $(p,pd)$ reaction, and experimental spectroscopic factors of the deuteron cluster are obtained by normalizing the experimental cross section to the theoretical computation. Consistent spectroscopic factors in comparison to shell-model expectations are obtained for transitions involving the orbital angular momentum $L=0$ of the cluster. The present work demonstrates that the $(p,pd)$ reactions at 226 MeV as a spectroscopic tool have an advantage in examining spectroscopic aspects of deuteron clustering and the mechanism to form a proton–neutron pair in the spin triplet state with negligible interference of final-state interactions and refraction effects.

A new experimental method to search for the double Gamow–Teller giant resonance using the double charge exchange ($^{12}$C, $^{12}$Be(0$^{+}_{2}$)) reaction is proposed and applied, for the first time, to a ^{48}$Ca target at 250 MeV/nucleon using a $^{12}$C primary beam at the RIKEN RI Beam Factory. The events with double isospin- and spin-flip in ^{48}$Ca were selected by measuring decay $\\gamma$-rays from ^{12}$Be(0$^{+}_{2}$). A forward-peaking component in the measured double-differential cross sections was observed with an integrated $0^\\circ$ cross section of $1.33 \\pm 0.12$ μb/sr in the excitation energy region below 34 MeV in ^{48}$Ti. Reaction analyses based on distorted-wave Born approximation calculations and the multipole decomposition based thereon indicate that $\\sim$40% of the forward-peaking component originates from the double Gamow–Teller transitions. The transition strength of the double Gamow–Teller transition is evaluated from the extracted forward-peaking cross section.

A gas cloud three times the mass of Earth is observed falling towards Sagittarius A*, the supermassive black hole at the centre of our Galaxy. The attractions of the Galactic Centre The radio source Sgr A* in Sagittarius is thought to be the site of a supermassive black hole lying at the centre of the Milky Way. A study of stellar orbits has identified an object moving towards Sgr A* at a speed of 1,700 kilometres per second. Its low temperature and spectral properties suggest that it is a dusty cloud of ionized gas, three times the mass of Earth, in the process of falling into the black hole. Models predict that as the cloud gets closer to the black hole, X-ray emissions will become much brighter, and a giant radiation flare may be emitted in a few years if the cloud breaks up and feeds gas into the black hole. Measurements of stellar orbits 1 , 2 , 3 provide compelling evidence 4 , 5 that the compact radio source Sagittarius A* at the Galactic Centre is a black hole four million times the mass of the Sun. With the exception of modest X-ray and infrared flares 6 , 7 , Sgr A* is surprisingly faint, suggesting that the accretion rate and radiation efficiency near the event horizon are currently very low 3 , 8 . Here we report the presence of a dense gas cloud approximately three times the mass of Earth that is falling into the accretion zone of Sgr A*. Our observations tightly constrain the cloud’s orbit to be highly eccentric, with an innermost radius of approach of only ∼3,100 times the event horizon that will be reached in 2013. Over the past three years the cloud has begun to disrupt, probably mainly through tidal shearing arising from the black hole’s gravitational force. The cloud’s dynamic evolution and radiation in the next few years will probe the properties of the accretion flow and the feeding processes of the supermassive black hole. The kilo-electronvolt X-ray emission of Sgr A* may brighten significantly when the cloud reaches pericentre. There may also be a giant radiation flare several years from now if the cloud breaks up and its fragments feed gas into the central accretion zone.

Stars with short orbital periods at the center of our Galaxy offer a powerful probe of a supermassive black hole. Over the past 17 years, the W. M. Keck Observatory has been used to image the galactic center at the highest angular resolution possible today. By adding to this data set and advancing methodologies, we have detected S0-102, a star orbiting our Galaxy's supermassive black hole with a period of just 11.5 years. S0-102 doubles the number of known stars with full phase coverage and periods of less than 20 years. It thereby provides the opportunity, with future measurements, to resolve degeneracies in the parameters describing the central gravitational potential and to test Einstein's theory of general relativity in an unexplored regime.

Two giant, linearly polarized radio lobes have been found emanating from the Galactic Centre, and are thought to originate in a biconical, star-formation-driven outflow from the Galaxy’s central 200 parsecs that transports a huge amount of magnetic energy, about 10 55 ergs, into the Galactic halo Magnetic outflows at the Galactic Centre A radio polarization survey of the southern sky with the Parkes Radio Telescope has revealed two huge, polarized radio lobes extending far out into the Galactic halo from the Galactic Centre region. The lobes are largely coincident with the 'Fermi bubbles', recently discovered regions of γ-ray emission reaching far above and below the Galactic Centre. The radio lobes are permeated by strong magnetic fields, and appear to originate as a biconical outflow driven by star formation rather than by a black hole. The nucleus of the Milky Way is known to harbour regions of intense star formation activity as well as a supermassive black hole 1 . Recent observations have revealed regions of γ-ray emission reaching far above and below the Galactic Centre (relative to the Galactic plane), the so-called ‘Fermi bubbles’ 2 . It is uncertain whether these were generated by nuclear star formation or by quasar-like outbursts of the central black hole 3 , 4 , 5 , 6 and no information on the structures’ magnetic field has been reported. Here we report observations of two giant, linearly polarized radio lobes, containing three ridge-like substructures, emanating from the Galactic Centre. The lobes each extend about 60 degrees in the Galactic bulge, closely corresponding to the Fermi bubbles, and are permeated by strong magnetic fields of up to 15 microgauss. We conclude that the radio lobes originate in a biconical, star-formation-driven (rather than black-hole-driven) outflow from the Galaxy’s central 200 parsecs that transports a huge amount of magnetic energy, about 10 55 ergs, into the Galactic halo. The ridges wind around this outflow and, we suggest, constitute a ‘phonographic’ record of nuclear star formation activity over at least ten million years.

Black hole physics: A new window on the Galactic Centre Using Very Long Baseline Interferometry (VLBI) at the relatively short radio wavelength of 1.3 mm, a new intrinsic size estimate has been obtained for Sagittarius A*, the supermassive black hole candidate at the centre of the Milky Way. The resulting lower limit on the size of Sgr A* is less than the predicted size of the event horizon of the presumed black hole, suggesting that Sgr A* emissions centre not on the black hole itself but on the surrounding accretion flow. VLBI observations of the Galactic Centre at around 1.3 mm, less influenced by interstellar scattering than those made at longer wavelengths, open a new window onto black-hole physics that will become even more sensitive as new VLBI stations are built. The cores of most large galaxies are thought to harbour super massive black holes. Sagittarius A*, the compact source of radio, infrared and x-ray emission at the centre of the Milky Way, is the closest example of this phenomenon. This paper reports observations that set a limit less than the expected apparent size of the event horizon of the presumed black hole, suggesting that the bulk of Sgr A* emission may not be centred on the black hole, but arises in the surrounding accretion flow. The cores of most galaxies are thought to harbour supermassive black holes, which power galactic nuclei by converting the gravitational energy of accreting matter into radiation 1 . Sagittarius A* (Sgr A*), the compact source of radio, infrared and X-ray emission at the centre of the Milky Way, is the closest example of this phenomenon, with an estimated black hole mass that is 4,000,000 times that of the Sun 2 , 3 . A long-standing astronomical goal is to resolve structures in the innermost accretion flow surrounding Sgr A*, where strong gravitational fields will distort the appearance of radiation emitted near the black hole. Radio observations at wavelengths of 3.5 mm and 7 mm have detected intrinsic structure in Sgr A*, but the spatial resolution of observations at these wavelengths is limited by interstellar scattering 4 , 5 , 6 , 7 . Here we report observations at a wavelength of 1.3 mm that set a size of microarcseconds on the intrinsic diameter of Sgr A*. This is less than the expected apparent size of the event horizon of the presumed black hole, suggesting that the bulk of Sgr A* emission may not be centred on the black hole, but arises in the surrounding accretion flow.