Accurate low temperature charge transport measurements in combination with high-precision x-ray diffraction experiments have allowed detection of the symmetry lowering in the single domain ...Tm0.19Yb0.81B12 crystals that belong to the family of dodecaborides with metal-insulator transition. Based on the fine structure analysis we discover the formation of dynamic charge stripes within the semiconducting matrix of Tm0.19Yb0.81B12. The charge dynamics in these conducting nano-size channels is characterized by broad-band optical spectroscopy that allowed estimating the frequency (~2.4 × 1011 Hz) of quantum motion of the charge carriers. It is suggested that cooperative Jahn-Teller effect in the boron sublattice is a cause of the large-amplitude rattling modes of the Tm and Yb ions responsible for the 'modulation' of the conduction band along one of the directions through the variation of 5d-2p hybridization of electron states.
In a superconductor that lacks inversion symmetry, the spatial part of the Cooper pair wave function has a reduced symmetry, allowing for the mixing of spin-singlet and spin-triplet Cooper pairing ...channels and thus providing a pathway to a non-trivial superconducting state. Materials with a non-centrosymmetric crystal structure and with strong spin-orbit coupling are a platform to realize these possibilities. Here, we report the synthesis and characterisation of high quality crystals of Sn4As3, with non-centrosymmetric unit cell (R3m). We have characterised the normal and superconducting states using a range of methods. Angle-resolved photoemission spectroscopy shows a multiband Fermi surface and the presence of two surface states, confirmed by density-functional theory calculations. Specific heat measurements reveal a superconducting critical temperature of Tc ∼ 1.14 K and an upper critical magnetic field of μ0Hc ≳ 7 mT, which are both confirmed by ultra-low temperature scanning tunneling microscopy and spectroscopy. Scanning tunneling spectroscopy shows a fully formed superconducting gap, consistent with conventional s-wave superconductivity.
For the first time, the possibility of producing silicene on CaF
2
/Si(111) substrates modified by electron irradiation is experimentally demonstrated. It is shown that areas of the planar surface of ...CaSi
2
with hexagonal packing formed under an electron beam can be used as a natural template for the subsequent growth of silicene. Silicon is deposited on such surfaces and the formation of silicene islands is confirmed by atomic force microscopy and Raman spectroscopy.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In this paper, it is shown using one-, two-, and three-dimensional spectrometry that the excursion distributions in random sequences of counts
of alpha-particle fluxes over the time interval
...correspond to the Poisson flow model and do not have periodic components. An example of
238
Pu source is used.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The paper reports complementary studies of the order parameter of the newly discovered iron-based superconductor, KCa
2
Fe
4
As
4
F
2
(
T
c
= 34 K), that consists of alternating blocks of KFe
2
As
2
...(122) phase and CaFeAsF (1111) phase. We performed high-resolution intrinsic multiple Andreev reflection spectroscopy supplemented with self-field critical current measurements. Andreev spectra obtained by means of a break-junction technique reveal two distinct superconducting order parameters Δ
L
and Δ
S
. Their temperature dependencies were measured from 1.5 K to
T
c
. The shapes of Andreev reflections dips, corresponding to the two gaps are symmetrical, which is a signature of
s
-wave order parameter. Temperature dependence of the self-field critical current can also be described by two
s
-wave gaps model.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The structure of the superconducting order parameter of weakly underdoped BaFe
1.92
Ni
0.08
As
2
pnictides with the critical temperature
T
c
≈ 18.2 K has been determined. Two microscopic ...superconducting order parameters—the small superconducting gap Δ
S
(0) and, supposedly, the edges of the large gap with anisotropy in the
ab
plane
and
—have been determined at
T
≪
T
c
, together with their temperature dependences, using incoherent multiple Andreev reflection spectroscopy. It has been shown that the determined temperature dependence of the lower critical field
H
c1
(
T
) can be described in the two-band approximation both within the so-called alpha model (using experimental Δ
S
(0),
, and
values) and using the temperature dependences Δ
S
(
T
) and
obtained by multiple Andreev reflection spectroscopy under the assumption of a fairly strong anisotropy of the small superconducting gap, where the experimental Δ
S
(0) value is taken as the outer edge of its angular distribution.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In this work, series of PAN membranes were prepared by the combined VIPS/NIPS method using different solvents. These membranes were investigated by using liquid-liquid displacement method for ...membrane pore size distribution and membrane permeance measurements. Wide range of pores size (30-60 nm) and membrane permeance up to 400 L/m2·h·bar were achieved depending on the casting conditions. It was shown that longer exposure in water vapor leads to higher pore size and at the same time makes membrane less permeable due to low asymmetry of porous structure..
We present detailed study of specific heat of FeSe single crystals with critical temperature Tc=8.45K at 0.4−200K in magnetic fields 0−9T. Analysis of the electronic specific heat at low temperatures ...shows the coexistence of isotropic s-wave gap and strongly anisotropic extended s-wave gap without nodes. It was found two possibilities of superconducting gap parameters which give equally description of experimental data: (i) two gaps with approximately equal amplitudes and weight contribution to specific heat: isotropic Δ1=1.7 meV (2Δ1/kBTc=4.7) and anisotropic gap with the amplitude Δ2max=1.8 meV (2Δ2max/kBTc=4.9 and anisotropy parameter m=0.85); (ii) two gaps with substantially different values: isotropic large gap Δ1=1.65 meV (2Δ1/kBTc=4.52) and anisotropic small gap Δ2max=0.75 meV (2Δ2max/kBTc=2) with anisotropy parameter m=0.71. These results are confirmed by the field behavior of the residual electronic specific heat γr.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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