138 research outputs found
Single-element 2D materials beyond graphene: methods of epitaxial synthesis
Today, two-dimensional materials are one of the key research topics for scientists around the world. Interest in 2D materials is not surprising because, thanks to their remarkable mechanical, thermal, electrical, magnetic, and optical properties, they promise to revolutionize electronics. The unique properties of graphene-like 2D materials give them the potential to create completely new types of devices for functional electronics, nanophotonics, and quantum technologies. This paper considers epitaxially grown two-dimensional allotropic modifications of single elements: graphene (C) and its analogs (transgraphenes) borophene (B), aluminene (Al), gallenene (Ga), indiene (In), thallene (Tl), silicene (Si), germanene (Ge), stanene (Sn), plumbene (Pb), phosphorene (P), arsenene (As), antimonene (Sb), bismuthene (Bi), selenene (Se), and tellurene (Te). The emphasis is put on their structural parameters and technological modes in the method of molecular beam epitaxy, which ensure the production of high-quality defect-free single-element two-dimensional structures of a large area for promising device applications
Measurement of the decay form factors in the OKA experiment
A precise measurement of the vector and axial-vector form factors difference
in the decay is presented.
About 95K events of are selected in
the OKA experiment. The result is .
Both errors are smaller than in the previous measurements.Comment: 9 pages, 8 figure
ab-plane tunneling and Andreev spectroscopy of superconducting gap and pseudogap in (Bi,Pb)2Sr2Ca2Cu3O10 and Bi2Sr2CaCu2O8
We have measured the temperature dependence of gap features revealed by
Andreev reflection Delta_s and by tunneling Delta in the ab-plane of optimal
and slightly overdoped microcrystals of (BiPb)2Sr2Ca2Cu3O10 (Bi2223) with
critical temperature Tc=110-115 K, and Bi2Sr2CaCu2O8 (Bi2212) with Tc=80-84 K.
The tunneling conductance of Bi2223-Insulator-Bi2223 junction shows peaks at
the 2Delta gap voltage, as well as dips and broad humps at other voltages. In
Bi2223, similarly to the well known Bi2212 spectra, the energies corresponding
to 2Delta, to the dip, and to the hump structure are in the ratio of 2:3:4.
This confirms that the dip and hump features are generic to the high
temperature superconductors, irrespective of the number of CuO2 layers or the
BiO superstructure. On the other hand, in both compounds Delta(T) and
Delta_s(T) dependences are completely different, and we conclude that the two
entities have different nature.Comment: LaTeX 2e, 17 pages, 7 figures in .eps forma
Experimental study of direct photon emission in K- --> pi- pi0 gamma decay using ISTRA+ detector
The branching ratio in the charged-pion kinetic energy region of 55 to 90 MeV
for the direct photon emission in the K- --> pi- pi0 gamma decay has been
measured using in-flight decays detected with the ISTRA+ setup operating in the
25 GeV/c negative secondary beam of the U-70 PS. The value
Br(DE)=[0.37+-0.39(stat)+-0.10(syst)]*10^(-5) obtained from the analysis of 930
completely reconstructed events is consistent with the average value of two
stopped-kaon experiments, but it differs by 2.5 standard deviations from the
average value of three in-flight-kaon experiments. The result is also compared
with recent theoretical predictions.Comment: 13 pages, 8 figure
Test of exotic scalar and tensor interactions in K_e3 decay using stopped positive kaons
The form factors of the decay K+ --> pi0 e+ nu (K_e3) have been determined
from the comparison of the experimental and Monte Carlo Dalitz distributions
containing about 10^5 K_e3 events. The following values of the parameters were
obtained: lambda_+ = 0.0278 +- 0.0017(stat) +- 0.0015(syst), f_S/f_+(0) =
0.0040 +- 0.0160(stat) +- 0.0067(syst) and f_T/f_+(0) = 0.019 +- 0.080(stat) +-
0.038(syst). Both scalar f_S and tensor f_T form factors are consistent with
the Standard Model predictions of zero values.Comment: 10 pages, 5 figures, contributed to the proceedings of NANP
Conference, Dubna, June 19-23, 200
Searches for the light invisible axion-like particle in decay
A high statistics data sample of the decays is recorded by the OKA
collaboration. A missing mass analysis is performed to search for a light
invisible pseudoscalar axion-like particle (ALP) in the decay . No signal is observed, the upper limits for the branching
ratio of the decay are calculated. The confidence level upper limit is
changing from to for the ALP mass from 0 to
200 MeV/, except for the region of mass, where the upper limit
is .Comment: 6 pages, 6 figure
Study of the K- -> pi0 e- nu decay
The decay K- -> pi0 e- nu has been studied using in-flight decays detected
with "ISTRA+" setup operating at the 25 GeV negative secondary beam of the U-70
PS. About 130K events were used for the analysis. The lambda_+ parameter of the
vector formfactor has been measured: lambda_+ = 0.0293 +- 0.0015(stat) +-
0.002(syst).
The limits on the possible tensor and scalar couplings have been derived:
f_T/f_+(0)=-0.044 +0.059 -0.057 (stat) f_S/f_+(0)=-0.020 +0.025 -0.016 (stat)Comment: 11 pages, Latex, 9 picture
Study of the decay in the OKA experiment
A high statistics data sample of the decays of mesons to three charged
particles was accumulated by the OKA experiment in 2012 and 2013. This allowed
to select a clean sample of about 450 events with
decays with the energy of the photon in
the kaon rest frame greater than 30 MeV. The measured branching fraction of the
, with > 30 MeV is . The measured energy spectrum of the decay photon is
compared with the prediction of the chiral perturbation theory to O. A
search for an up-down asymmetry of the photon with respect to the hadronic
system decay plane is also performed.Comment: 9 pages, 7 figures, 1 tabl
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