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At least 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Parallel Broadband Femtosecond Reflection Spectroscopy at a Soft X-Ray Free-Electron Laser

X-ray absorption spectroscopy (XAS) and the directly linked X-ray reflectivity near absorption edges yield a wealth of specific information on the electronic structure around the resonantly addressed element. Observing the dynamic response of complex materials to optical excitations in pump–probe experiments requires high sensitivity to small changes in the spectra which in turn necessitates the brilliance of free electron laser (FEL) pulses. However, due to the fluctuating spectral content of pulses generated by self-amplified spontaneous emission (SASE), FEL experiments often struggle to reach the full sensitivity and time-resolution that FELs can in principle enable. Here, we implement a setup which solves two common challenges in this type of spectroscopy using FELs: First, we achieve a high spectral resolution by using a spectrometer downstream of the sample instead of a monochromator upstream of the sample. Thus, the full FEL bandwidth contributes to the measurement at the same time, and the FEL pulse duration is not elongated by a monochromator. Second, the FEL beam is divided into identical copies by a transmission grating beam splitter so that two spectra from separate spots on the sample (or from the sample and known reference) can be recorded in-parallel with the same spectrometer, enabling a spectrally resolved intensity normalization of pulse fluctuations in pump–probe scenarios. We analyze the capabilities of this setup around the oxygen K- and nickel L-edges recorded with third harmonic radiation of the free electron laser in Hamburg (FLASH), demonstrating the capability for pump–probe measurements with sensitivity to reflectivity changes on the per mill level.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3V by Materials Project

VK3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent K sites. In the first K site, K is bonded to four equivalent K and four equivalent V atoms to form a mixture of distorted corner, edge, and face-sharing KK4V4 tetrahedra. All K–K bond lengths are 3.99 Å. All K–V bond lengths are 3.99 Å. In the second K site, K is bonded in a body-centered cubic geometry to eight equivalent K atoms. V is bonded in a body-centered cubic geometry to eight equivalent K atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3W by Materials Project

K3W is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent K sites. In the first K site, K is bonded to four equivalent K and four equivalent W atoms to form a mixture of distorted corner, edge, and face-sharing KK4W4 tetrahedra. All K–K bond lengths are 3.91 Å. All K–W bond lengths are 3.91 Å. In the second K site, K is bonded in a body-centered cubic geometry to eight equivalent K atoms. W is bonded in a body-centered cubic geometry to eight equivalent K atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3Sc by Materials Project

K3Sc is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent K sites. In the first K site, K is bonded to four equivalent K and four equivalent Sc atoms to form a mixture of distorted face, edge, and corner-sharing KK4Sc4 tetrahedra. All K–K bond lengths are 4.13 Å. All K–Sc bond lengths are 4.13 Å. In the second K site, K is bonded in a body-centered cubic geometry to eight equivalent K atoms. Sc is bonded in a body-centered cubic geometry to eight equivalent K atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3Sn by Materials Project

K3Sn is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent K sites. In the first K site, K is bonded to four equivalent K and four equivalent Sn atoms to form a mixture of distorted corner, edge, and face-sharing KK4Sn4 tetrahedra. All K–K bond lengths are 3.85 Å. All K–Sn bond lengths are 3.85 Å. In the second K site, K is bonded in a body-centered cubic geometry to eight equivalent K atoms. Sn is bonded in a body-centered cubic geometry to eight equivalent K atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3Tl by Materials Project

K3Tl is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent K sites. In the first K site, K is bonded to four equivalent K and four equivalent Tl atoms to form a mixture of distorted corner, edge, and face-sharing KK4Tl4 tetrahedra. All K–K bond lengths are 4.05 Å. All K–Tl bond lengths are 4.05 Å. In the second K site, K is bonded in a body-centered cubic geometry to eight equivalent K atoms. Tl is bonded in a body-centered cubic geometry to eight equivalent K atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3Cd by Materials Project

K3Cd is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent K sites. In the first K site, K is bonded to four equivalent K and four equivalent Cd atoms to form a mixture of distorted corner, edge, and face-sharing KK4Cd4 tetrahedra. All K–K bond lengths are 4.06 Å. All K–Cd bond lengths are 4.06 Å. In the second K site, K is bonded in a body-centered cubic geometry to eight equivalent K atoms. Cd is bonded in a body-centered cubic geometry to eight equivalent K atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3Co by Materials Project

K3Co is alpha bismuth trifluoride structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent K sites. In the first K site, K is bonded in a 12-coordinate geometry to four equivalent K and four equivalent Co atoms. All K–K bond lengths are 3.98 Å. All K–Co bond lengths are 3.98 Å. In the second K site, K is bonded to eight equivalent K and four equivalent Co atoms to form a mixture of distorted corner, edge, and face-sharing KK8Co4 cuboctahedra. All K–Co bond lengths are 4.18 Å. Co is bonded in a distorted body-centered cubic geometry to twelve K atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3Cr by Materials Project

K3Cr is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent K sites. In the first K site, K is bonded to four equivalent K and four equivalent Cr atoms to form a mixture of distorted corner, edge, and face-sharing KK4Cr4 tetrahedra. All K–K bond lengths are 4.02 Å. All K–Cr bond lengths are 4.02 Å. In the second K site, K is bonded in a body-centered cubic geometry to eight equivalent K atoms. Cr is bonded in a body-centered cubic geometry to eight equivalent K atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3Hf by Materials Project

K3Hf is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent K sites. In the first K site, K is bonded to four equivalent K and four equivalent Hf atoms to form a mixture of distorted face, edge, and corner-sharing KK4Hf4 tetrahedra. All K–K bond lengths are 3.98 Å. All K–Hf bond lengths are 3.98 Å. In the second K site, K is bonded in a body-centered cubic geometry to eight equivalent K atoms. Hf is bonded in a body-centered cubic geometry to eight equivalent K atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3Os by Materials Project

K3Os is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent K sites. In the first K site, K is bonded to four equivalent K and four equivalent Os atoms to form a mixture of distorted face, edge, and corner-sharing KK4Os4 tetrahedra. All K–K bond lengths are 3.59 Å. All K–Os bond lengths are 3.59 Å. In the second K site, K is bonded in a 8-coordinate geometry to eight equivalent K and six equivalent Os atoms. All K–Os bond lengths are 4.14 Å. Os is bonded in a body-centered cubic geometry to fourteen K atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K5SnBi3 by Materials Project

K5SnBi3 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are five inequivalent K sites. In the first K site, K is bonded to four Bi atoms to form a mixture of distorted edge and corner-sharing KBi4 tetrahedra. There are a spread of K–Bi bond distances ranging from 3.61–3.83 Å. In the second K site, K is bonded in a distorted see-saw-like geometry to four Bi atoms. There are a spread of K–Bi bond distances ranging from 3.62–3.86 Å. In the third K site, K is bonded in a 4-coordinate geometry to one Sn and three Bi atoms. The K–Sn bond length is 3.91 Å. There are a spread of K–Bi bond distances ranging from 3.66–3.79 Å. In the fourth K site, K is bonded to four Bi atoms to form a mixture of distorted edge and corner-sharing KBi4 tetrahedra. There are a spread of K–Bi bond distances ranging from 3.60–3.63 Å. In the fifth K site, K is bonded in a 6-coordinate geometry to two equivalent Sn and four Bi atoms. There are one shorter (3.89 Å) and one longer (3.94 Å) K–Sn bond lengths. There are a spread of K–Bi bond distances ranging from 3.71–4.07 Å. Sn is bonded in a 7-coordinate geometry to three K and four Bi atoms. There are a spread of Sn–Bi bond distances ranging from 2.96–3.05 Å. There are three inequivalent Bi sites. In the first Bi site, Bi is bonded in a 8-coordinate geometry to seven K and one Sn atom. In the second Bi site, Bi is bonded in a 7-coordinate geometry to five K and two equivalent Sn atoms. In the third Bi site, Bi is bonded in a 8-coordinate geometry to seven K and one Sn atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

The magnetic order in multiferroic DyMnO 3

We report that with flexibility in tuning their electric and magnetic properties, multiferroics can be used in information exchange and storage in ways that are very different from the present electronic materials. Here we use resonant soft X-ray scattering spectroscopy to study the F-type (0,τ,0) and C-type (0, 1–2τ, 0) diffraction peaks from sinusoidal antiferromagnetic spin order in multiferroic DyMnO 3 . By comparing the temperature dependence of ordering wave vectors τ, peak intensities I, and correlation lengths λ measured at Mn L 2 - , O K-, and Dy M 5 -edges, we show that the nearly perfect locking between the ordering wave vectors from Dy 4f states and Mn 3d orbitals manifesting the second harmonic diffraction peak implies the notable orbital involvement in the coupling between Mn and Dy spins. Our DFT calculations further suggest that the lattice response to different antiferromagnetic ground states (A-type versus E-type) is much weaker in TbMnO 3 , in agreement with previous claim that the symmetric exchange interaction can be an important factor for understanding the ferroelectricity in DyMnO 3 than in TbMnO 3 .

36 MATERIALS SCIENCE↗
DOE OSTI2025

A Flat Analyzer Polycapillary Spectrometer for X-ray Absorption Spectroscopy of Dilute Transition Metals at X-ray-Free Electron Lasers

X-ray absorption spectroscopy (XAS) coupled with highly intense pulses from an X-ray-free electron laser (XFEL) can be used to track ultrafast chemical dynamics. Nonetheless, measurements for dilute samples (≤1 mM) have been exceptionally challenging, as scattering background signals dominate over the sample’s X-ray fluorescence. We show that femtosecond time-resolved XAS measurements of sub-millimolar transition metal solutions are now possible at the Linac Coherent Light Source (LCLS) using a high-throughput polycapillary XAS spectrometer, designed, developed, and commissioned at LCLS and the Stanford Synchrotron Radiation Lightsource (SSRL). The instrument integrates three polycapillary optics that collect and collimate X-ray fluorescence emitted from the interaction point with a high solid angle. X-ray collimated fluorescence is then selectively diffracted by coupled graphite analyzer crystals. As a result, the contribution of scattered photons is suppressed. Experiments at the Pt L 3 -edge on 0.1 mM aqueous K 2 PtCl 6 (delivered via a 100 μm liquid jet) were successfully performed in the laser pump X-ray probe configuration at the LCLS XCS and XPP instruments. We report the transient spectra of hexachloroplatinate within the first 10 ps after a 266 nm photoexcitation. We observed a short-lived reduced intermediate (≈2 ps). The polycapillary X-ray spectrometer at LCLS now enables the efficient study of the dynamics of ultradilute transition metals in solution. This capability opens the door to investigating plasmonic systems, photocatalysts, enzymes, and other scarce and dilute samples.

LCLS↗
DOE OSTI2020

Chiral topologically ordered insulating phases in arrays of interacting integer quantum Hall islands

Here, we study networks of Coulomb-blockaded integer quantum Hall islands with even fillings ν = 2 k ( k being an integer), including cases with 2 k layers each of ν = 1 fillings. Allowing only spin-current interactions between the islands (i.e., without any charge transfer), we obtain solvable models leading to a rich set of insulating S U ( 2 ) k topologically ordered phases. The case with k = 1 is dual to the Kalmeyer-Laughlin phase, k = 2 to Kitaev's chiral spin liquid and the Moore-Read state, and k = 3 contains a Fibonacci anyon that may be utilized for universal topological quantum computation. Additionally, we show how the S U ( 2 ) k topological phases may be obtained also in an array of islands with ν = 2 k integer quantum Hall states and critical spin chains in a checkerboard pattern. The array and checkerboard constructions gap out the charge mode and additional “flavor” modes by virtue of their geometry. Furthermore, we find that a fine tuning of the system parameter is not needed in the checkerboard configuration and the ν = 2 case. We also discuss their bulk excitations, and show that their thermal Hall conductance is universal, reflecting the central charge c = 3 k / ( k + 2 ) of the chiral edge modes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Materials Data on KAg3S2 by Materials Project

KAg3S2 crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. K1+ is bonded to six equivalent S2- atoms to form edge-sharing KS6 octahedra. All K–S bond lengths are 3.29 Å. Ag1+ is bonded in a distorted bent 150 degrees geometry to two equivalent S2- atoms. Both Ag–S bond lengths are 2.47 Å. S2- is bonded in a 6-coordinate geometry to three equivalent K1+ and three equivalent Ag1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KTe by Materials Project

KTe crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to six equivalent Te1- atoms to form edge-sharing KTe6 octahedra. All K–Te bond lengths are 3.68 Å. In the second K1+ site, K1+ is bonded in a 6-coordinate geometry to six equivalent Te1- atoms. All K–Te bond lengths are 3.56 Å. Te1- is bonded in a 7-coordinate geometry to six K1+ and one Te1- atom. The Te–Te bond length is 2.84 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K2O by Materials Project

K2O is Fluorite structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. K1+ is bonded to four equivalent O2- atoms to form a mixture of corner and edge-sharing KO4 tetrahedra. All K–O bond lengths are 2.81 Å. O2- is bonded in a body-centered cubic geometry to eight equivalent K1+ atoms.

36 MATERIALS SCIENCE↗