67 research outputs found
Shot noise of Coulomb drag current
We work out a theory of shot noise in a special case. This is a noise of the
Coulomb drag current excited under the ballistic transport regime in a
one-dimensional nanowire by a ballistic non-Ohmic current in a nearby parallel
nanowire. We predict sharp oscillation of the noise power as a function of gate
voltage or the chemical potential of electrons. We also study dependence of the
noise on the voltage V across the driving wire. For relatively large values of
V the noise power is proportional to V^2.Comment: 9 pages, 2 figure
Phonon drag in ballistic quantum wires
The acoustic phonon-mediated drag-contribution to the drag current created in
the ballistic transport regime in a one-dimensional nanowire by phonons
generated by a current-carrying ballistic channel in a nearby nanowire is
calculated. The threshold of the phonon-mediated drag current with respect to
bias or gate voltage is predicted.Comment: 5 pages, 2 figure
Stability of microprocessor relay protection and automation systems against intentional destructive electromagnetic impacts. Part 2
Problems of impact of electromagnetic high-power pulses generated at nuclear explosion or by means of special equipment intended specially for damage of electronic equipment, in particular, digital protective relays and automatic systems, along with ways of protection against these impacts are considered
Stability of microprocessor relay protection and automation systems against intentional destructive electromagnetic impacts. Part 1
Problems of impact of electromagnetic high-power pulses generated at nuclear explosion or by means of special equipment intended specially for damage of electronic equipment, in particular, digital protective relays and automatic systems, along with ways of protection against these impacts are considered
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Theory of femtosecond photon echo decay in semiconductors
The authors investigate a mechanism responsible for the observed very short times of the photon echo decay (of the order of a few femtoseconds) in semiconductors. It is associated with the loss of phase memory as a result of interaction of the mixed state (associated with interband transitions) with an unscreened random Coulomb potential of the photocarriers or with a random static potential of the impurities. Qualitative physical consideration enabling one to visualize the process of echo decay are presented. They have introduced a new time characteristic of a system of interacting electrons. This is the time of phase breaking, {tau}{sub {var_phi}} which they calculate within the eikonal approximation using a diagrammatic technique. It is shown that {tau}{sub {var_phi}} is typically much shorter than both the period of plasma oscillations and the time of electron-electron collisions. The screening of Coulomb potential cannot build up during this time. {tau}{sub {var_phi}} is proportional to n{sup {minus}1/d} (where n is the carrier concentration, d the dimensionality of a system) which is consistent with the experimental results
Acoustoelectric pumping through a ballistic point contact in the presence of magnetic fields
The acoustoelectric current, J, induced in a ballistic point contact (PC) by
a surface acoustic wave is calculated in the presence of a perpendicular
magnetic field, B. It is found that the dependence of the current on the Fermi
energy in the terminals is strongly correlated with that of the PC conductance:
J is small at the conductance plateaus, and is large at the steps. Like the
conductance, the acoustoelectric current has the same functional behavior as in
the absence of the field, but with renormalized energy scales, which depend on
the strength of the magnetic field, | B|.Comment: 7 page
Realistic Tunneling States for the Magnetic Effects in Non-Metallic Real Glasses
The discovery of magnetic and compositional effects in the low temperature
properties of multi-component glasses has prompted the need to extend the
standard two-level systems (2LSs) tunneling model. A possible extension
\cite{Jug2004} assumes that a subset of tunneling quasi-particles is moving in
a three-welled potential (TWP) associated with the ubiquitous inhomogeneities
of the disordered atomic structure of the glass. We show that within an
alternative, cellular description of the intermediate-range atomic structure of
glasses the tunneling TWP can be fully justified. We then review how the
experimentally discovered magnetic effects can be explained within the approach
where only localized atomistic tunneling 2LSs and quasi-particles tunneling in
TWPs are allowed. We discuss the origin of the magnetic effects in the heat
capacity, dielectric constant (real and imaginary parts), polarization echo and
SQUID magnetization in several glassy systems. We conclude by commenting on a
strategy to reveal the mentioned tunneling states (2LSs and TWPs) by means of
atomistic computer simulations and discuss the microscopic nature of the
tunneling states in the context of the potential energy landscape of
glass-forming systems.Comment: 48 pages, 27 figures; mini-review for the Proceedings of the XIV
International Workshop on Complex Systems (Fai della Paganella, Trento, March
2015) (submitted to Phil.Mag.). arXiv admin note: text overlap with
arXiv:cond-mat/0210221 by other author
Antiferromagnetic resonance in ferroborate NdFe(BO)$_4
The AFMR spectra of the NdFe(BO) crystal are measured in a wide
range of frequencies and temperatures. It is found that by the type of magnetic
anisotropy the compound is an "easy-plane" antiferromagnet with a weak
anisotropy in the basal plane. The effective magnetic parameters are
determined: anisotropy fields =1.14 kOe and =60 kOe and
magnetic excitation gaps =101.9 GHz and =23.8 GHz.
It is shown that commensurate-incommensurate phase transition causes a shift in
resonance field and a considerable change in absorption line width.
At temperatures below 4.2 K nonlinear regimes of AFMR excitation at low
microwave power levels are observed
Coulomb Drag Between Parallel Ballistic Quantum Wires
The Coulomb drag between parallel, {\it ballistic} quantum wires is studied
theoretically in the presence of a perpendicular magnetic field B. The
transresistance R_D shows peaks as a function of the Fermi level and splitting
energy between the 1D subbands of the wires. The sharpest peaks appear when the
Fermi level crosses the subband extrema so that the Fermi momenta are small.
Two other kinds of peaks appear when either {\it intra}- or {\it inter}-subband
transitions of electrons have maximum probability; the {\it intra}-subband
transitions correspond to a small splitting energy. R_D depends on the field B
in a nonmonotonic fashion: it decreases with B, as a result of the suppression
of backscattering, and increases sharply when the Fermi level approaches the
subband bottoms and the suppression is outbalanced by the increase of the
Coulomb matrix elements and of the density of states.Comment: Text 14 pages in Latex/Revtex format, 4 Postscript figures. Phys.
Rev. B,in pres
Mesoscopic fluctuations of Coulomb drag between quasi-ballistic 1D-wires
Quasiballistic 1D quantum wires are known to have a conductance of the order
of 2e^2/h, with small sample-to-sample fluctuations. We present a study of the
transconductance G_12 of two Coulomb-coupled quasiballistic wires, i.e., we
consider the Coulomb drag geometry. We show that the fluctuations in G_12
differ dramatically from those of the diagonal conductance G_ii: the
fluctuations are large, and can even exceed the mean value, thus implying a
possible reversal of the induced drag current. We report extensive numerical
simulations elucidating the fluctuations, both for correlated and uncorrelated
disorder. We also present analytic arguments, which fully account for the
trends observed numerically.Comment: 10 pages including 7 figures. Minor changes according to referee
report. Accepted for PR
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