252 research outputs found
Andreev reflection at point contacts with heavy-fermion UBe13 ?
We comment on a recent Letter by Waelti et al. (PRL 84, 5616 (2000)) on
'Spectroscopic evidence for unconventional superconductivity in UBe13'. We show
- by using the basic Wexler formula - that it is unlikely to observe Andreev
reflection at point contacts between UBe13 and a normal metal. The large
superconducting anomalies usually found for those contacts are mainly due to
the resistive Maxwell resistance vanishing below Tc of UBe13.Comment: 1 page, no figures, RevTeX, submitted to Phys. Rev. Let
Development of Regional Maximum Permissible Concentrations of Oil, Lead, Chromium, Nickel, and Copper in the Ordinary Black Soils of Central Ciscaucasia
Contamination of ordinary chernozems of the Central Ciscaucasia with oil, lead, chromium, nickel and copper leads to a deterioration in their biological indicators. A significant decrease in the number of microflora, enzymatic activity and inhibition of the state of plants was established. The ecotoxicity sequence of heavy metals for ordinary black soils of Central Ciscaucasia is the following: Cr > Pb ≥Cu ≥ Ni. Ordinary black soils of Central Ciscaucasia, compared to similar black soils of Western Ciscaucasia, are somewhat less resistant to pollution with chromium, but are more resistant to pollution with copper and nickel. Resistance to pollution with lead and oil is the same. Regional maximum permissible concentrations of oil, lead, chromium, nickel and copper have been set for ordinary black soils of Central Ciscaucasia, based on disruptions of the environmental and the agricultural functions of the soil
decays revisited: branching ratios and T-odd momenta correlations
We calculate the branching ratios of the decays, and the T-odd triple momenta correlations
, due to the
electromagnetic final state interaction, in these processes. The contributions
on the order of and to the corresponding amplitudes
are treated exactly. For the branching ratios, the corrections on the order of
are estimated and demonstrated to be small. We compare the results
with those of other authors. In some cases our results differ considerably from
the previous ones.Comment: 13 pages, 11 figures; references adde
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
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
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
Evidence for spin mixing in holmium thin film and crystal samples
144518Quantum Matter and Optic
- …