110 research outputs found
The possibility of using «1c: enterprise» in the educational process
Article is devoted to the possibility of using the products of 1C in the learning processСтатья посвящена возможности использования продуктов фирмы 1С в учебном процесс
Role of pair-breaking and phase fluctuations in c-axis tunneling in underdoped BiSrCaCuO
The Josephson Plasma Resonance is used to study the c-axis supercurrent in
the superconducting state of underdoped
BiSrCaCuO with varying degrees of controlled
point-like disorder, introduced by high-energy electron irradiation. As
disorder is increased, the Josephson Plasma frequency decreases proportionally
to the critical temperature. The temperature dependence of the plasma frequency
does not depend on the irradiation dose, and is in quantitative agreement with
a model for quantum fluctuations of the superconducting phase in the CuO
layers.Comment: 2 pages, submitted to the Proceedings of M2S-HTSC VIII Dresde
Collective responses of Bi-2212 stacked junction to 100 GHz microwave radiation under magnetic field oriented along the c-axis
We studied a response of Bi-2212 mesa type structures to 100 GHz microwave
radiation. We found that applying magnetic field of about 0.1 T across the
layers enables to observe collective Shapiro step response corresponding to a
synchronization of all 50 intrinsic Josephson junctions (IJJ) of the mesa. At
high microwave power we observed up to 10th harmonics of the fundamental
Shapiro step. Besides, we found microwave induced flux-flow step position of
which is proportional to the square root of microwave power and that can exceed
at high enough powers 1 THz operating frequency of IJJ oscillations.Comment: 11 pages including 5 figures, accepted for publication in JETP
Letter
The emergence of quantum capacitance in epitaxial graphene
We found an intrinsic redistribution of charge arises between epitaxial
graphene, which has intrinsically n-type doping, and an undoped substrate. In
particular, we studied in detail epitaxial graphene layers thermally elaborated
on C-terminated - (- ()). We have investigated
the charge distribution in graphene-substrate systems using Raman spectroscopy.
The influence of the substrate plasmons on the longitudinal optical phonons of
the substrates has been detected. The associated charge redistribution
reveals the formation of a capacitance between the graphene and the substrate.
Thus, we give for the first time direct evidence that the excess negative
charge in epitaxial monolayer graphene could be self-compensated by the
substrate without initial doping. This induced a previously unseen
redistribution of the charge-carrier density at the substrate-graphene
interface. There a quantum capacitor appears, without resorting to any
intentional external doping, as is fundamentally required for epitaxial
graphene. Although we have determined the electric field existing inside the
capacitor and revealed the presence of a minigap () for
epitaxial graphene on - face terminated carbon, it remains small in
comparison to that obtained for graphene on face terminated . The
fundamental electronic properties found here in graphene on substrates
may be important for developing the next generation of quantum technologies and
electronic/plasmonic devices.Comment: 26 pages, 8 figures, available online as uncorrected proof, Journal
of Materials Chemistry C (2016
Controlling high-frequency collective electron dynamics via single-particle complexity
We demonstrate, through experiment and theory, enhanced high-frequency
current oscillations due to magnetically-induced conduction resonances in
superlattices. Strong increase in the ac power originates from complex
single-electron dynamics, characterized by abrupt resonant transitions between
unbound and localized trajectories, which trigger and shape propagating charge
domains. Our data demonstrate that external fields can tune the collective
behavior of quantum particles by imprinting configurable patterns in the
single-particle classical phase space.Comment: 5 pages, 4 figure
Vortex Solid-Liquid Transition in BiSrCaCuO with a High Density of Strong Pins
The introduction of a large density of columnar defects in %underdoped
BiSrCaCuO crystals does not, at sufficiently low
vortex densities, increase the irreversibility line beyond the first order
transition (FOT) field of pristine crystals. At such low fields, the flux line
wandering length behaves as in pristine
%BiSrCaCuO crystals. Next, vortex positional
correlations along the --axis in the vortex Bose glass at fields above the
FOT are smaller than in the low--field vortex solid. Third, the
Bose-glass-to-vortex liquid transition is signaled by a rapid decrease in
c-axis phase correlations. These observations are understood in terms of the
``discrete superconductor'' model.Comment: 4 pages, 4 figures Submitted to Phys. Rev. B Rapid Comm. 16-1-2004
Revised version 18-3-200
Vortex fluctuations in underdoped Bi2Sr2CaCu2O8+d crystals
Vortex thermal fluctuations in heavily underdoped Bi2Sr2CaCu2O8+d (Tc=69.4 K)
are studied using Josephson plasma resonance (JPR). From the data in zero
magnetic field, we obtain the penetration depth along the c-axis,
lambda_{L,c}(0) = 229 micrometers and the anisotropy ratio gamma(0) = 600. The
low plasma frequency allows us to study phase correlations over the whole
vortex solid (Bragg-glass) state. The JPR results yield a wandering length
r_{w} of vortex pancakes. The temperature dependence of r_{w} as well as its
increase with applied dc magnetic field can only be explained by the
renormalization of the tilt modulus by thermal fluctuations, and suggest the
latter is responsible for the dissociation of the vortices at the first order
transition.Comment: 4 pages, 5 figures. Submitted to Phys. Rev. Let
Distribution of pairing functions in superconducting spin valve SF1F2
The distribution of the spin-singlet component, the short-range spin-triplet component with zero projection, and the long-range spin-triplet component with projection ±1 of the superconducting pairing function has been obtained for different regimes of switching of a spin valve with a three-layer heterostructure (superconductor/ferromagnet/ferromagnet). The distribution of the components is discussed as the main reason for the behavior of the superconducting transition temperature as a function of the angle between the magnetic moments of the ferromagnetic layers in these regimes
A rotating cavity for high-field angle-dependent microwave spectroscopy of low-dimensional conductors and magnets
The cavity perturbation technique is an extremely powerful method for
measuring the electrodynamic response of a material in the millimeter- and
sub-millimeter spectral range (10 GHz to 1 THz), particularly in the case of
high-field/frequency magnetic resonance spectroscopy. However, the application
of such techniques within the limited space of a high-field magnet presents
significant technical challenges. We describe a 7.62 mm x 7.62 mm (diameter x
length) rotating cylindrical cavity which overcomes these problems.Comment: 11 pages including 8 figure
Magnetic field tunable vortex diode made of YBa2Cu3O7−δ Josephson junction asymmetrical arrays
Several Josephson ratchets designed as asymmetrically structured parallel-series arrays of Josephson junctions made of YBa2Cu3O7−δ have been fabricated. From the current-voltage characteristics measured for various values of applied magnetic field, B, in the temperature range of 10–89 K, we demonstrate that the devices work as magnetic field-tunable highly reversible vortex diodes. Thus, at 89 K, the ratchet efficiency η could be reversed from +60% to −60% with a change in B as small as 3 μT. By decreasing the operation temperature, η improves up to −95% at 10 K while the dynamics in the B-tunability degrades. The ratchet designs we propose here can be used to control unidirectional vortex flow vortices in superconducting devices as well as building integrated nano-magnetic sensors. Numerical simulations qualitatively confirm our experimental findings and also provide insight into the related and more general problem of the control of the transport of nano/quantum objects in thin films
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