34 research outputs found
Dynamic Localization in Quantum Wires
In the paper the dynamic localization of charged particle (electron) in a
quantum wire under the external non-uniform time-dependent electric field is
considered. The electrons are trapped in a deep 'dynamic' quantum wells which
are the result of specific features of the potential imposed on 2D electron
gas: the scale of spatial nonuniformity is much smaller then the electron mean
free path (L_1 << \bar{l}) and the frequency is much greater then \tau^{-1},
where \tau is the electron free flight time. As a result, the effect of this
field on the charged particle is in a sense equivalent to the effect of a
time-independent effective potential, that is a sequence of deep 'dynamic'
quantum wells were the elelctrons are confined. The possible consequeces of
this effect are also discussed and similarity with the classical Paul traps are
emphasized.Comment: 21 pages, 1 figur
On the environmental decoherence and spin interference in mesoscopic loop structures
Mechanisms of 'environmental decoherence' such as surface scattering,
Elliot-Yafet process and precession mechanisms, as well as their influence on
the spin phase relaxation are considered and compared. It is shown that the
'spin ballistic' regime is possible, when the phase relaxation length for the
spin part of the wave function (WF)is much greater than the phase relaxation
length for the 'orbital part'. In the presence of an additional magnetic field,
the spin part of the electron's WF acquires a phase shift due to additional
spin precession about that field. If the structure length is chosen to be
greater than the phase relaxation length for the 'orbital part' and less than
the phase relaxation length for the spin part of WF, it is possible to 'wash
out' the quantum interference related to the phase coherence of the 'orbital
part' of the WF, retaining at the same time that related to the phase coherence
of the spin part and, hence, to reveal corresponding conductance oscillations
Spin ballistic transport and quantum intreference in mesoscopic loop structures
In the paper, a simple theory of quantum inteference in a loop structure caused by spin coherent transport and the Larmor precession of the electron spin is presented. A “spin ballistic” regime is supposed to occur, when the phase relaxation length for the spin part of the wavefunction (Lϕ(s)) is much greater than the phase relaxation length for the “orbital part” (Lϕ(e)) . In the presence of an additional magnetic field, the spin part of the electron wavefunction acquires a phase shift due to additional spin precession around that field. If the structure length L is chosen to be (Lϕ(s)) > L > (Lϕ(e)), it is possible to “wash out” the quantum interference related to the phase coherence of the “orbital part” of the wavefunction, retaining at the same time that related to the phase coherence of the spin part and, hence, to reveal corresponding conductance oscillations. Different mechanisms of spin relaxation, such as Elliot – Yafet, the scattering by the edges and surface the structure and the precession ones, as well as their influence on the spin coherent transport are considered. The quantum interference in time-dependent magnetic field, quantum beats in mesoscopic loop structure, are also discussed. The similarities between this effect and Josephson, scalar Aharonov – Bohm and Aharonov – Casher effects, as well as their differences are treated and possible application of the effect to the construction of the device, complementary to superconducting quantum interference device is analyzed
Hybrid quantum-classical chaotic NEMS
We present an exactly solvable model of a hybrid quantum-classical system of
a Nitrogen-Vacancy (NV) center spin (quantum spin) coupled with a
nanocantilever (classical) and analyze the enforcement of the regular or
chaotic classical dynamics onto to the quantum spin dynamics. The main problem
we focus in this paper is whether the classical dynamical chaos may induce
chaotic quantum effects in the spin dynamics. We explore several characteristic
criteria of the quantum chaos, such as quantum Poincar\'e recurrences,
generation of coherence and energy level distribution and observe interesting
chaotic effects in the spin dynamics. Dynamical chaos imposed in the cantilever
dynamics through the kicking pulses induces the stochastic dynamics of the
quantum subsystem. However, we show that this type of stochasticity does not
possess all the characteristic features of the quantum chaos and is distinct
from it. The phenomenon of the hybrid quantum-classical chaos leads to
dynamical freezing of the NV spin.Comment: 13 pages, 7 figure
Massey products in symplectic manifolds
The paper is devoted to study of Massey products in symplectic manifolds.
Theory of generalized and classical Massey products and a general construction
of symplectic manifolds with nontrivial Massey products of arbitrary large
order are exposed. The construction uses the symplectic blow-up and is based on
the author results, which describe conditions under which the blow-up of a
symplectic manifold X along its submanifold Y inherits nontrivial Massey
products from X ot Y. This gives a general construction of nonformal symplectic
manifolds.Comment: LaTeX, 48 pages, 2 figure
Exotic smooth structures and symplectic forms on closed manifolds
We give a short proof of the (known) result that there are no Kaehler
structures on exotic tori. This yields a negative solution to a problem posed
by Benson and Gordon. W discuss the symplectic version of the problem and
analyze results which yield an evidence for the conjecture that there are no
symplectic structures on exotic tori.Comment: AMSLaTeX, 16 pages, a new version. A survey of the symplectic version
of the problem is adde
Magnetospectroscopy of symmetric and anti-symmetric states in double quantum wells
The experimental results obtained for the magneto-transport in the
InGaAs/InAlAs double quantum wells (DQW) structures of two different shapes of
wells are reported. The beating-effect occurred in the Shubnikov-de Haas (SdH)
oscillations was observed for both types of the structures at low temperatures
in the parallel transport when magnetic field was perpendicular to the layers.
An approach to the calculation of the Landau levels energies for DQW structures
was developed and then applied to the analysis and interpretation of the
experimental data related to the beating-effect. We also argue that in order to
account for the observed magneto-transport phenomena (SdH and Integer Quantum
Hall effect), one should introduce two different quasi-Fermi levels
characterizing two electron sub-systems regarding symmetry properties of their
states, symmetric and anti-symmetric ones which are not mixed by
electron-electron interaction.Comment: 20 pages, 20 figure