Development of ultrafast four-dimensional precession electron diffraction.

Ultrafast electron diffraction/microscopy technique enables us to investigate the nonequilibrium dynamics of crystal structures in the femtosecond-nanosecond time domain. However, the electron diffraction intensities are in general extremely sensitive to the excitation errors (i.e.

Development and applications of ultrafast transmission electron microscopy.

We present a review on the development and applications of ultrafast transmission electron microscopy (UTEM) at Institute of Physical and Chemical Research (RIKEN). We introduce the UTEM system for the pump-probe transmission electron microscopy (TEM) observation in a wide temporal range. By combining the UTEM and pixelated detector, we further develop five-dimensional scanning TEM (5D STEM), which provides the ultrafast nanoscale movie of physical quantities in nanomaterials, such as crystal lattice information and electromagnetic field, by convergent-beam electron diffraction (CBED) and differential phase contrast imaging technique.

Characterizing an Optically Induced Sub-micrometer Gigahertz Acoustic Wave in a Silicon Thin Plate.

Optically induced GHz-THz guided acoustic waves have been intensively studied because of the potential to realize noninvasive and noncontact material inspection. Although the generation of photoinduced guided acoustic waves utilizing nanostructures, such as ultrathin plates, nanowires, and materials interfaces, is being established, experimental characterization of these acoustic waves in consideration of the finite size effect has been difficult due to the lack of experimental methods with nm × ps resolution. Here we experimentally observe the sub-micrometer guided acoustic waves in a nanofabricated ultrathin silicon plate by ultrafast transmission electron microscopy with nm × ps precision.

Development of five-dimensional scanning transmission electron microscopy.

By combining the scanning transmission electron microscopy with the ultrafast optical pump-probe technique, we improved the time resolution by a factor of ∼10 for the differential phase contrast and convergent-beam electron diffraction imaging. These methods provide ultrafast nanoscale movies of physical quantities in nano-materials, such as crystal lattice deformation, magnetization vector, and electric field. We demonstrate the observations of the photo-induced acoustic phonon propagation with an accuracy of 4 ps and 8 nm and the ultrafast demagnetization under zero magnetic field with 10 ns and 400 nm resolution, by utilizing these methods.

Visualizing optically-induced strains by five-dimensional ultrafast electron microscopy.

Ultrafast optical control of strain is crucial for the future development of nanometric acoustic devices. Although ultrafast electron microscopy has played an important role in the visualization of strain dynamics in the GHz frequency region, quantitative strain evaluation with nm × ps spatio-temporal resolution is still challenging. Five-dimensional scanning transmission electron microscopy (5D-STEM) is a powerful technique that measures time-dependent diffraction or deflection of the electron beam at the respective two-dimensional sample positions in real space.

Discovery of mesoscopic nematicity wave in iron-based superconductors.

Nematicity is ubiquitous in the electronic phases of iron-based superconductors. The order parameter that characterizes the nematic phase has been investigated in momentum space, but its real-space arrangement remains largely unexplored. We use linear dichroism (LD) in a low-temperature laser–photoemission electron microscope to map out the nematic order parameter of nonmagentic FeSe and antiferromagnetic BaFe(AsP).

Nano-to-micro spatiotemporal imaging of magnetic skyrmion's life cycle.

Magnetic skyrmions are self-organized topological spin textures that behave like particles. Because of their fast creation and typically long lifetime, experimental verification of skyrmion's creation/annihilation processes has been challenging. Here, we successfully track skyrmion dynamics in defect-introduced CoZnMn by using pump-probe Lorentz transmission electron microscope.

Finite-element simulation of photoinduced strain dynamics in silicon thin plates.

In this paper, we investigate the femtosecond-optical-pulse-induced strain dynamics in relatively thin (100 nm) and thick (10 000 nm) silicon plates based on finite-element simulations. In the thin sample, almost spatially homogeneous excitation by the optical pulse predominantly generates a standing wave of the lowest-order acoustic resonance mode along the out-of-plane direction. At the same time, laterally propagating plate waves are emitted at the sample edge through the open edge deformation.

Nanoscale Imaging of Unusual Photoacoustic Waves in Thin Flake VTe.

The control of acoustic phonons, which are the carriers of sound and heat, has become the focus of increasing attention because of a demand for manipulating the sonic and thermal properties of nanometric devices. In particular, the photoacoustic effect using ultrafast optical pulses has a promising potential for the optical manipulation of phonons in the picosecond time regime. So far, its mechanism has been mostly based on the commonplace thermoelastic expansion in isotropic media, which has limited applicability.

Switching of band inversion and topological surface states by charge density wave.

Topologically nontrivial materials host protected edge states associated with the bulk band inversion through the bulk-edge correspondence. Manipulating such edge states is highly desired for developing new functions and devices practically using their dissipation-less nature and spin-momentum locking. Here we introduce a transition-metal dichalcogenide VTe, that hosts a charge density wave (CDW) coupled with the band inversion involving V3d and Te5p orbitals.

Gigahertz-repetition-rate, narrowband-deep-ultraviolet light source for minimization of acquisition time in high-resolution angle-resolved photoemission spectroscopy.

Ultrahigh-repetition-rate (1.1 GHz), deep-ultraviolet coherent light at 208.8 nm is generated by applying an external Fabry-Pérot cavity for repetition-rate multiplication to the fourth harmonics of a 10-ps, mode-locked Ti:sapphire laser.

Ultrafast nematic-orbital excitation in FeSe.

The electronic nematic phase is an unconventional state of matter that spontaneously breaks the rotational symmetry of electrons. In iron-pnictides/chalcogenides and cuprates, the nematic ordering and fluctuations have been suggested to have as-yet-unconfirmed roles in superconductivity. However, most studies have been conducted in thermal equilibrium, where the dynamical property and excitation can be masked by the coupling with the lattice.

Ultrafast dissolution and creation of bonds in IrTe induced by photodoping.

The observation and control of interweaving spin, charge, orbital, and structural degrees of freedom in materials on ultrafast time scales reveal exotic quantum phenomena and enable new active forms of nanotechnology. Bonding is the prime example of the relation between electronic and nuclear degrees of freedom. We report direct evidence illustrating that photoexcitation can be used for ultrafast control of the breaking and recovery of bonds in solids on unprecedented time scales, near the limit for nuclear motions.

[Agreement in the responses to self-reported and proxy-reported versions of QOL-HC: a new quality-of-life scale for patients receiving home-based medical care].

Aim: We developed quality-of-life (QOL) scales for patients receiving home medical care. The objective of this study was to examine the agreement between the scores of the scales answered by patients and those answered by their proxy, as cognitive decline may interfere with one's ability to understand complex topics, such as the QOL.

Methods: Participants were pairs of patients receiving home medical care and their proxy.

Orbital-anisotropic electronic structure in the nonmagnetic state of BaFe(AsP ) superconductors.

High-temperature superconductivity in iron-pnictides/chalcogenides arises in balance with several electronic and lattice instabilities. Beside the antiferromagnetic order, the orbital anisotropy between Fe 3d and 3d occurs near the orthorhombic structural transition in several parent compounds. However, the extent of the survival of orbital anisotropy against the ion-substitution remains to be established.

Large magneto-thermopower in MnGe with topological spin texture.

Quantum states characterized by nontrivial topology produce interesting electrodynamics and versatile electronic functionalities. One source for such remarkable phenomena is emergent electromagnetic field, which is the outcome of interplay between topological spin structures with scalar spin chirality and conduction electrons. However, it has scarcely been exploited for emergent function related to heat-electricity conversion.

Superconducting gap anisotropy sensitive to nematic domains in FeSe.

The structure of the superconducting gap in unconventional superconductors holds a key to understand the momentum-dependent pairing interactions. In superconducting FeSe, there have been controversial results reporting nodal and nodeless gap structures, raising a fundamental issue of pairing mechanisms of iron-based superconductivity. Here, by utilizing polarization-dependent laser-excited angle-resolved photoemission spectroscopy, we report a detailed momentum dependence of the gap in single- and multi-domain regions of orthorhombic FeSe crystals.

Antiferroic electronic structure in the nonmagnetic superconducting state of the iron-based superconductors.

A major problem in the field of high-transition temperature () superconductivity is the identification of the electronic instabilities near superconductivity. It is known that the iron-based superconductors exhibit antiferromagnetic order, which competes with the superconductivity. However, in the nonmagnetic state, there are many aspects of the electronic instabilities that remain unclarified, as represented by the orbital instability and several in-plane anisotropic physical properties.

Factors associated with polypharmacy in elderly home-care patients.

Aim: Polypharmacy, which is often observed in elderly patients, has been associated with several unfavorable outcomes, including an increased risk of potentially inappropriate medications, medication non-adherence, drug duplication, drug-drug interactions, higher healthcare costs and adverse drug reactions. A significant association between polypharmacy and adverse outcomes among older people living in the community has also been confirmed. A reduction in the number of medications should thus be pursued for many older individuals.

Factors associated with unexpected admissions and mortality among low-functioning older patients receiving home medical care.

Aim: The need for and availability of home medical care for elderly patients with limitations in terms of access to medical facilities has been increasing. We investigated the association between low function, malnutrition, dementia and multicomorbidity with patient prognosis, focusing on unexpected hospital admissions and mortality in elderly non-cancer patients receiving home care.

Methods: The study included 124 Japanese patients receiving home medical care in the form of regular visits from doctors and nurses for physical and/or mental disability.

Electron and lattice dynamics of transition metal thin films observed by ultrafast electron diffraction and transient optical measurements.

We report the ultrafast dynamics of electrons and lattice in transition metal thin films (Au, Cu, and Mo) investigated by a combination of ultrafast electron diffraction (UED) and pump-probe optical methods. For a single-crystalline Au thin film, we observe the suppression of the diffraction intensity occuring in 10 ps, which direcly reflects the lattice thermalization via the electron-phonon interaction. By using the two-temperature model, the electron-phonon coupling constant () and the electron and lattice temperatures (, ) are evaluated from UED, with which we simulate the transient optical transmittance.

Risk Factors for the Discontinuation of Home Medical Care among Low-functioning Older Patients.

Objectives: Older patients receiving home medical care often have declining functional status and multiple disease conditions. It is important to identify the risk factors for care transition events in this population in order to avoid preventable transitions. In the present study, therefore, we investigated the factors associated with discontinuation of home medical care as a potentially preventable care transition event in older patients.

Development and validation of a new quality of life scale for patients receiving home-based medical care: The Observational Study of Nagoya Elderly with Home Medical Care.

Aim: To develop and validate a scale that assesses quality of life in patients receiving home-based medical care.

Methods: A new quality of life scale was developed and evaluated in four phases: (i) item generation; (ii) first field study with a 14-item questionnaire; (iii) preliminary validation study, to reduce the number of items to four; and (iv) second field study comprising 40 patients, to evaluate the validity of the final version. Participants were requested to answer both the final version of the scale and the Short Form-8, to enable identification of any relationship between the two.

Anisotropy of the superconducting gap in the iron-based superconductor BaFe2(As(1-x)P(x))2.

We report peculiar momentum-dependent anisotropy in the superconducting gap observed by angle-resolved photoemission spectroscopy in BaFe2(As(1-x)P(x))2 (x = 0.30, Tc = 30 K). Strongly anisotropic gap has been found only in the electron Fermi surface while the gap on the entire hole Fermi surfaces are nearly isotropic.

Redox control and high conductivity of nickel bis(dithiolene) complex π-nanosheet: a potential organic two-dimensional topological insulator.

A bulk material comprising stacked nanosheets of nickel bis(dithiolene) complexes is investigated. The average oxidation number is -3/4 for each complex unit in the as-prepared sample; oxidation or reduction respectively can change this to 0 or -1. Refined electrical conductivity measurement, involving a single microflake sample being subjected to the van der Pauw method under scanning electron microscopy control, reveals a conductivity of 1.