682 research outputs found
Microscopic analysis of the chemical reaction between Fe(Te,Se) thin films and underlying CaF
To understand the chemical reaction at the interface of materials, we
performed a transmission electron microscopy (TEM) observation in four types of
Fe(Te,Se) superconducting thin films prepared on different types of substrates:
CaF2 substrate, CaF2 substrate with a CaF2 buffer layer, CaF2 substrate with a
FeSe buffer layer, and a LaAlO3 substrate with a CaF2 buffer layer. Based on
the energy-dispersive X-ray spectrometer (EDX) analysis, we found possible
interdiffusion between fluorine and selenium that has a strong influence on the
superconductivity in Fe(Te,Se) films. The chemical interdiffusion also plays a
significant role in the variation of the lattice parameters. The lattice
parameters of the Fe(Te,Se) thin films are primarily determined by the chemical
substitution of anions, and the lattice mismatch only plays a secondary role.Comment: 30 pages, 9 figur
Point-contact Andreev-reflection spectroscopy in Fe(Te,Se) films: multiband superconductivity and electron-boson coupling
We report on a study of the superconducting order parameter in
Fe(TeSe) thin films (with different Se contents: x=0.3, 0.4, 0.5)
by means of point-contact Andreev-reflection spectroscopy (PCARS). The PCARS
spectra show reproducible evidence of multiple structures, namely two clear
conductance maxima associated to a superconducting gap of amplitude and additional shoulders at higher energy that, as we
show, are the signature of the strong interaction of charge carriers with a
bosonic mode whose characteristic energy coincides with the spin-resonance
energy. The details of some PCARS spectra at low energy suggest the presence of
a smaller and not easily discernible gap of amplitude . The existence of this gap and its amplitude are confirmed by PCARS
measurements in Fe(TeSe) single crystals. The values of the two
gaps and , once plotted as a function of the local
critical temperature , turn out to be in perfect agreement with the
results obtained by various experimental techniques reported in literature.Comment: 8 pages, 6 figures. This is an author-created, un-copyedited version
of an article published in Supercond. Sci. Technol. IOP Publishing Ltd is not
responsible for any errors or omissions in this version of the manuscript or
any version derived from it. The Version of Record is available online at
10.1088/0953-2048/27/12/12401
Pure nematic state in iron-based superconductor
Lattice and electronic states of thin FeSe films on LaAlO substrates are
investigated in the vicinity of the nematic phase transition. No evidence of
structural phase transition is found by x-ray diffraction below K, while results obtained from resistivity measurement and angle-resolved
photoemission spectroscopy clearly show the appearance of a nematic state.
These results indicate formation of a pure nematic state in the iron-based
superconductor and provide conclusive evidence that the nematic state
originates from the electronic degrees of freedom. This pure nematicity in the
thin film implies difference in the electron-lattice interaction from bulk FeSe
crystals. FeSe films provide valuable playgrounds for observing the pure
response of "bare" electron systems free from the electron-lattice interaction,
and should make important contribution to investigate nematicity and its
relationship with superconductivity
Extractability and chemical forms of radioactive cesium in designated wastes investigated in an on-site test
In the aftermath of the 2011 accident at Fukushima Daiichi Nuclear Power Plant (F1 hereafter), municipal solid waste (MSW) contaminated with radioactive cesium (rad-Cs hereafter) has been generated in 12 prefectures in Japan. The Japanese Minister of Environment classified MSW that contained rad-Cs in the concentration more than 8,000 Bq/kg as “designated (solid) waste (DSW hereafter), and prescribed the collection, storage and transportation procedures. When MSW containing rad-Cs was incinerated, rad-Cs was concentrated in fly ash, and the ash often fell into the category of DSW. We have investigated a technique that can reduce the volume of the rad-Cs-contaminated fly-ash by extracting rad-Cs with aqueous solvents such as water and oxalic acid and concentrating rad-Cs in a small amount of hexacyanoferrate (or ferrocyanide, designated as Fer hereafter) precipitate. Since DSW could not be transported to the outside laboratory, we have conducted on-site tests at places where DSW were generated to investigate the applicability of the extraction – precipitation technique. The present report is a summary of our most recent on-site test conducted in 2014. Also presented is the re-evaluation of the results of our past on-site test from the viewpoint of leaching of rad-Cs and heavy metals in the fly ash. An apparent decrease in leaching of rad-Cs from fly ash was observed by incinerating sewage sludge with soil. Fly ash from a melting furnace contained more water-soluble rad-Cs than that from a fluidized-bed incinerator. Some incinerator fly ash appeared to produce rad-Cs in colloidal form when extracted with oxalic acid, resulting in the lower removal of rad-Cs from the extract by Fer method. © The Editor(s) if applicable and the Author(s) 2016
Dark matter wants Linear Collider
One of the main purposes of physics at the International Linear Collider (ILC) is to study the property of dark matter such as its mass, spin, quantum numbers, and interactions with particles of the standard model. We discuss how the property can or cannot be investigated at the ILC using two typical cases of dark matter scenario: i) most of new particles predicted in physics beyond the standard model are heavy and only dark matter is accessible at the ILC, and ii) not only dark matter but also other new particles are accessible at the ILC. We find that, as can be easily imagined, dark matter can be detected without any difficulties in the latter case. In the former case, it is still possible to detect dark matter when the mass of dark matter is less than a half mass of the higgs boson
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