244 research outputs found
Structure and magnetism of Fe thin films grown on Rh(001) studied by photoelectron spectroscopy
Morphology of drawn syndiotactic polypropylene films
Morphological studies were conducted to investigate the drawability of melt-quenched (MQ) and slowly cooled (MSC) films of syndiotactic polypropylene (sPP) with a high syndiotactic pentad fraction. Transmission electron microscopy (TEM) using the ruthenium tetraoxide staining and ultrathin sectioning method revealed that amorphous chains as the matrix of MQ film played a role in drawability of the film by their alignment to machine direction (MD) and partial crystallizations into nanofibrils. On the other hand, the initial strain induced, rotations of clusters of long lamellar crystals as the major entity of MSC film accompanying breaks of long lamellae and formation of crazes and microvoids at the cluster boundary. Compared with a homogeneous thinning of MQ film by drawing, ca. 100 nm-thick layer slips along MD and parallel to the film surface took place in MSC film. This gave rise to the formation of V-shaped bent lamellar morphology and their further break into a smaller cluster of stacked lamellae which were aligned oblique by ca. 35 from MD. With elongation, some nanofibrils formed from chains generated by the partial breaks of lamellae are aligned perpendicular to the remained oblique lamellae and others parallel to MD in region where lamellar morphology almost disappeared. No chain slips in the nanofibrils can be related to a low elongation at break, i.e. a low ductility of sPP films. The lower elongation at break for MSC film than for MQ one can be interpreted by microvoids initially formed in the neck region and later moved to the fully drawn part, the microvoids initiating the break of the drawn film
Valley spin polarization by using the extraordinary Rashba effect on silicon
The addition of the valley degree of freedom to a two-dimensional spin-polarized electronic system provides the opportunity to multiply the functionality of next-generation devices. So far, however, such devices have not been realized due to the difficulty to polarize the valleys, which is an indispensable step to activate this degree of freedom. Here we show the formation of 100% spin-polarized valleys by a simple and easy way using the Rashba effect on a system with C-3 symmetry. This polarization, which is much higher than those in ordinary Rashba systems, results in the valleys acting as filters that can suppress the backscattering of spin-charge. The present system is formed on a silicon substrate, and therefore opens a new avenue towards the realization of silicon spintronic devices with high efficiency.X114334Nsciescopu
Observation of spin-polarized bands and domain-dependent Fermi arcs in polar Weyl semimetal MoTe
We investigate the surface electronic structures of polar 1T'-MoTe2, the Weyl
semimetal candidate realized through the nonpolar-polar structural phase
transition, by utilizing the laser angle-resolved photoemission spectroscopy
(ARPES) combined with first-principles calculations. Two kinds of domains with
different surface band dispersions are observed from a single-crystalline
sample. The spin-resolved measurements further reveal that the spin
polarizations of the surface and the bulk-derived states show the different
domain-dependences, indicating the opposite bulk polarity. For both domains,
some segment-like band features resembling the Fermi arcs are clearly observed.
The patterns of the arcs present the marked contrast between the two domains,
respectively agreeing well with the slab calculation of (0 0 1) and (0 0 -1)
surfaces. The present result strongly suggests that the Fermi arc connects the
identical pair of Weyl nodes on one side of the polar crystal surface, whereas
it connects between the different pairs of Weyl nodes on the other side.Comment: 13 pages, 4 figure
Time-, spin-, and angle-resolved photoemission spectroscopy with a 1-MHz 10.7-eV pulse laser
We describe a setup of time-, spin-, and angle-resolved photoemission
spectroscopy (tr-SARPES) employing a 10.7-eV (=115.6 nm) pulse laser
at 1-MHz repetition rate as a probe photon source. This equipment effectively
combines technologies of a high-power Yb:fiber laser, ultraviolet-driven
harmonic generation in Xe gas, and a SARPES apparatus equipped with
very-low-energy-electron-diffraction (VLEED) spin detectors. A high repetition
rate (1 MHz) of the probe laser allows experiments with the photoemission
space-charge effects significantly reduced, despite a high flux of 10
photons/s on the sample. The relatively high photon energy (10.7 eV) also
brings the capability of observing a wide momentum range that covers the entire
Brillouin zone of many materials while ensuring high momentum resolution. The
experimental setup overcomes a low efficiency of spin-resolved measurements,
which gets even more severe for the pump-probed unoccupied states, and affords
for investigating ultrafast electron and spin dynamics of modern quantum
materials with energy and time resolutions of 25 meV and 360 fs, respectively.Comment: 11 pages, 7 figure
Origins of thermal spin depolarization in half-metallic ferromagnet CrO
Using high-resolution spin-resolved photoemission spectroscopy, we observed a
thermal spin depolarization to which all spin-polarized electrons contribute.
Furthermore we observed a distinct minority spin state near the Fermi level and
a corresponding depolarization that seldom contributes to demagnetization. The
origin of this depolarization has been identified as the many-body effect
characteristics of half-metallic ferromagnets. Our investigation opens an
experimental field of itinerant ferromagnetic physics focusing on phenomena
with sub-meV energy scale.Comment: 19 pages, 10 figure
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