Superconducting and mesoscopic structures
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Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України
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| Цитувати: | Superconducting and mesoscopic structures / A.N. Omelyanchouk // Физика низких температур. — 2004. — Т. 30, № 7-8. — С. 687-688. — англ. |
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Omelyanchouk, A.N. 2017-06-13T09:35:56Z 2017-06-13T09:35:56Z 2004 Superconducting and mesoscopic structures / A.N. Omelyanchouk // Физика низких температур. — 2004. — Т. 30, № 7-8. — С. 687-688. — англ. 0132-6414 https://nasplib.isofts.kiev.ua/handle/123456789/120902 en Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України Физика низких температур Сверхпроводимость и мезоскопические структуры Superconducting and mesoscopic structures Article published earlier |
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Superconducting and mesoscopic structures |
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Superconducting and mesoscopic structures Omelyanchouk, A.N. Сверхпроводимость и мезоскопические структуры |
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Superconducting and mesoscopic structures |
| title_full |
Superconducting and mesoscopic structures |
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Superconducting and mesoscopic structures |
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Superconducting and mesoscopic structures |
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superconducting and mesoscopic structures |
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Omelyanchouk, A.N. |
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Omelyanchouk, A.N. |
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Сверхпроводимость и мезоскопические структуры |
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Сверхпроводимость и мезоскопические структуры |
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2004 |
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English |
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Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України |
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0132-6414 |
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https://nasplib.isofts.kiev.ua/handle/123456789/120902 |
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Superconducting and mesoscopic structures / A.N. Omelyanchouk // Физика низких температур. — 2004. — Т. 30, № 7-8. — С. 687-688. — англ. |
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2025-11-26T16:32:13Z |
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1850628178378227712 |
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Superconducting and mesoscopic structures
(Preface)
It is remarkable, that for 40 years the Josephson ef-
fect maintains its position in the centre of condensed
matter physics. The reason is, probably, in the very
concept of weak coherent coupling between macro-
scopic quantum systems. It allows to separate the ef-
fects of interaction, which creates the long-range or-
der, from the correlation themselves, corresponding to
this order. It provided the possibility to investigate
the overlap of mutually exclusive (in the bulk)
long-range orders. It gives the opportunity to look at
the effects of finite size of the system. Josephson effect
also gives the framework for discussing and realization
of macroscopic quantum phenomena (beyond the al-
most trivial fact that superconductors are macroscopic
quantum objects). Last five years saw the demonstra-
tion of macroscopic quantum resonant tunneling,
quantum coherence and quantum entanglement in
Josephson structures. Josephson physics repaid the
physics of bulk superconductivity by providing means
of investigations of unusual superconductors (e.g., de-
monstrating d-wave symmetry in high-Tc cuprates).
Brian D. Josephson discovered his remarkable
effect in 1962. Josephson predicted that a zero voltage
supercurrent could flow in a junction between two
superconductors separated by a tunnel barrier. The
magnitude of the Josephson current is related to the
difference of the phases of the macroscopic wave
functions (complex order parameters) of supercon-
ductors forming the junction. P.W. Anderson and
J.M. Rowell first observed this dc Josephson effect in
1963. If a dc voltage V is applied to the junction, ac
supercurrent with the frequency 2eV/� appears bet-
ween the superconductors. The first direct observation
of the ac Josephson effect was done 40 years ago in
Kharkov (I.K. Yanson, V.M. Svistunov, and I.M.
Dmitrenko, Zh. Exp. Teor. Fiz. 47, 2091 (1964); ibid.
48, 976 (1965)). Soon after Josephson’s predictions for
the tunnel junctions, it became clear that the effects are
much more general and occur whenever two supercon-
ductors are weakly coupled. The physics of weak
superconductivity (term introduced by P.W. Ander-
son) became an area of a great interest for experimental
and theoretical investigations. More than forty years
after its discovery, the Josephson effect still attracts
considerable attention and keeps providing us with
new exciting physics and applications.
This issue is devoted to aspects of the physics of
superconducting and mesoscopic structures. It repre-
sents reviews and original articles on the subject. The
papers by Yanson and Dmitrenko, which are opening of
the issue, review the initial steps in study of the ac
Josephson effect in tunnel junctions and further experi-
mental investigation of weakly coupled superconductors
at Kharkov’s Institute for Low Temperature Physics and
Engineering.
The Josephson effect arises in superconducting
weak links — junctions of two weakly coupled super-
conductors (massive banks) S1 and S2. The coupling
allows the exchange by electrons between the banks
and establishes the superconducting phase coherence
in the system as a whole. The weakness of the coupling
means that the superconducting order parameters of
the banks are essentially the same as for disconnected
superconductors, and they are characterized by the
phases of the order parameters �1 and �2. The Joseph-
son weak link can be considered as a «mixer» of the
two superconducting macroscopic quantum states in
the banks. The result of the mixing is a phase depen-
dent current carrying state with current flowing from
one bank to another. This current is determined (para-
meterized) by the phase difference � � �� �2 1 across
weak link. The specific form of the current–phase
relation I( )� depends on the type of the weak link.
A number of papers consider the coherent transport
in Josephson weak links with coupling more comp-
licated then the just tunneling barrier. In the paper by
Kulik different types of superconducting weak links
are reviewed, focusing on the origin of jumps in
current–phase dependencies. The author discusses as
well persistent currents in the mesoscopic and nano-
scopic Aharonov–Bohm structures. Novel effects in
superconducting nanojunctions are studied theore-
tically in the paper by Zaikin. It is shown, that
interplay between quantum interference effects and
Andreev reflection in S–N–S junctions with insulating
barriers may qualitatively modify the Josephson cur-
rent. Several papers included deal with spin effects in
mesoscopic Josephson junctions. Shnirman et al. study
the dynamics of a single spin embedded in the
tunneling barrier between two superconductors. New
effect of the «Josephson nutation» is predicted. The
paper by Krive et al. reviews the charge and spin effects
in S–Luttinger liquid–S and S–quantum wire–S
junctions.
The properties of the current carrying states in a
weak link depend not only on the coupling manner
but also on the properties of the superconducting
banks. The modern physics of superconductivity is
essentially the physics of unconventional supercon-
ductivity. The discovery of d-wave symmetry of the
order parameter in high-temperature superconductors
and of triplet superconductivity in compound Sr2RuO4
has caused a stream of theoretical and experimental
research of unconventional superconductors. The sensi-
tivity of Josephson effect to the symmetry of the comp-
lex order parameter in the junction’s banks stimulated
numerous studies of Josephson weak links between
unconventional superconductors. The current–phase re-
lations for unconventional Josephson weak links are
quite different from the conventional ones. For ex-
ample, in grain boundary junctions, depending on the
angle of miss-orientation of d-wave order parameters
in the banks, the current–phase relation is changed
from sin( )� like curve to �sin( )2� dependence.
Clearly, it determines new features in behavior of such
Josephson junctions in applied voltage or magnetic
field. Considerable number of papers included con-
cerns the study of unconventional Josephson weak
links. One of the most striking manifestations of the
unconventional order parameter symmetry is the ap-
pearance, together with the Josephson current, of the
spontaneous current flowing along the contact
interface. The spontaneous current arises due to the
breaking of the time-reversal symmetry (T) in the
system. The study of T-breaking phenomena is not only
of a fundamental significance but also attracts interest
from the point of realization of qubits, basic units of
quantum computers. The review by Kolesnichenko et
al. focuses on spontaneous currents in junctions
between d-wave and triplet superconductors. It also
contains the review of superconducting qubits basics
with emphasizing on the properties of d-wave qubits.
A theoretical paper by Tanaka et al. considers the
impurity scattering effect on charge transport in
high-Tc cuprate junctions. The results of experimental
investigations of high-Tc grain boundary junctions
and heterostructures are presented in the papers by
Tafuri et al., Komissinski et al. and Timofeev et al.
The specific features of ac Josephson effect in
unconventional superconductors are reported in the
theoretical paper by Kwon et al. Note that the
problem of existence of fractional ac Josephson effect
in unconventional superconductors needs further theo-
retical and experimental investigations.
Mesoscopic structures, consisting of several Joseph-
son junctions, are studied now intensively from the
point of view of qubit realization. A paper by Il’ichev
et al. summarizes the results of implementation of the
advanced impedance measurements technique for
characterization of interferometer-type superconduc-
ting qubits. In a theoretical paper by Ioffe et al. a new
class of Josephson arrays is introduced. These arrays
have nontrivial topology and exhibit novel quantum
states at low temperatures. In the paper by Kuple-
vakhky, the detail theory of Josephson vortices in
layered superconductors is developed. The quantum
dynamics of order parameter and time dependent BCS
pairing in the frame of Wigner distribution function is
investigated by Amin et al.
A single issue cannot cover all aspects of the
research. It gives the reader a brief overview of the
current state of activities, which, we hope, will be
useful and will stimulate further investigations in the
field of superconducting and mesoscopic structures.
We greatly appreciate helpful discussions with all
the contributors during the preparation of this issue.
A.N. Omelyanchouk
688 Fizika Nizkikh Temperatur, 2004, v. 30, Nos. 7/8
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