192 research outputs found
Abrupt metal-insulator transition observed in VO2 thin films induced by a switching voltage pulse
An abrupt metal-insulator transition (MIT) was observed in VO2 thin films
during the application of a switching voltage pulse to two-terminal devices.
Any switching pulse over a threshold voltage for the MIT of 7.1 V enabled the
device material to transform efficiently from an insulator to a metal. The
characteristics of the transformation were analyzed by considering both the
delay time and rise time of the measured current response. The extrapolated
switching time of the MIT decreased down to 9 ns as the external load
resistance decreased to zero. Observation of the intrinsic switching time of
the MIT in the correlated oxide films is impossible because of the
inhomogeneity of the material; both the metallic state and an insulating state
co-exist in the measurement volume. This indicates that the intrinsic switching
time is in the order of less than a nanosecond. The high switching speed might
arise from a strong correlation effect (Coulomb repulsion) between the
electrons in the material.Comment: 5 pages, 5 figure
Formation of the hotel business model based on the network management form
The competitive advantages, acquired by hotels using the network form of business organization, have been highlighted. Based on the analysis of the diverse opinions of specialists, the concept of a «hotel chain» has been clarified. Тhe difference between the concepts of «hotel chain» and «hotel brand» has been shown. The features of the formation of hotel chains in Russia have been emphasized. A management contract and its components, that require agreement between the hotel operator and the owner of an independent hotel, have been considered. The prospectivity for an independent hotel to conclude with a hotel operator of a franchise agreement with a view to joining the network has been shown. The data on the amount of franchisee contributions to franchisor from various hotel operators for certain hotel brands in 2018 have been presented
Bilayer manganites: polarons in the midst of a metallic breakdown
The exact nature of the low temperature electronic phase of the manganite
materials family, and hence the origin of their colossal magnetoresistant (CMR)
effect, is still under heavy debate. By combining new photoemission and
tunneling data, we show that in La{2-2x}Sr{1+2x}Mn2O7 the polaronic degrees of
freedom win out across the CMR region of the phase diagram. This means that the
generic ground state is that of a system in which strong electron-lattice
interactions result in vanishing coherent quasi-particle spectral weight at the
Fermi level for all locations in k-space. The incoherence of the charge
carriers offers a unifying explanation for the anomalous charge-carrier
dynamics seen in transport, optics and electron spectroscopic data. The
stacking number N is the key factor for true metallic behavior, as an
intergrowth-driven breakdown of the polaronic domination to give a metal
possessing a traditional Fermi surface is seen in the bilayer system.Comment: 7 pages, 2 figures, includes supplementary informatio
Tunneling electroresistance effect in ferroelectric tunnel junctions at the nanoscale
Stable and switchable polarization of ferroelectric materials opens a
possibility to electrically control their functional behavior. A particularly
promising approach is to employ ferroelectric tunnel junctions where the
polarization reversal in a ferroelectric barrier changes the tunneling current
across the junction. Here, we demonstrate the reproducible tunneling
electroresistance effect using a combination of Piezoresponse Force Microscopy
(PFM) and Conducting Atomic Force Microscopy (C-AFM) techniques on
nanometer-thick epitaxial BaTiO3 single crystal thin films on SrRuO3 bottom
electrodes. Correlation between ferroelectric and electronic transport
properties is established by the direct nanoscale visualization and control of
polarization and tunneling current in BaTiO3 films. The obtained results show a
change in resistance by about two orders of magnitude upon polarization
reversal on a lateral scale of 20 nm at room temperature. These results are
promising for employing ferroelectric tunnel junctions in non-volatile memory
and logic devices, not involving charge as a state variable.Comment: 18 pages, 4 figure
Stability and damping with the electromechanical system of turning of rotor excavators in the process of operation
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