共查询到20条相似文献,搜索用时 15 毫秒
1.
G. E. Volovik 《JETP Letters》1997,65(6):491-496
In d-wave superconductors the electronic entropy associated with an isolated vortex diverges logarithmically with the size of
the system even at low temperatures. In the vortex array the entropy per vortex per layer, S
V
, is much larger than k
B
and depends on the distribution of the velocity field v
s
around the vortex. If there is a first-order transition upon a change of the velocity distribution, then there will be a
big entropy jump ΔS
V
∼k
B
at the transition. This entropy jump comes from the electronic degrees of freedom on the vortex background, which is modified
by the vortex transition. This can explain the big jump in the entropy observed in the so-called vortex-melting transition
[A. Junod, M. Roulin, J-Y. Genoud et al., Physica C, to be published], in which the vortex array and thus the velocity field are redistributed. The possibility of
the Berezinskii-Kosterlitz-Thouless transition in the 3-dimensional d-wave superconductor due to the fermionic bound states in the vortex background is discussed.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 6, 465–469 (25 March 1997)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
2.
G. E. Volovik 《JETP Letters》1996,63(9):763-769
The spectrum of the fermion zero modes in the vicinity of a vortex with fractional winding number is discussed. This is inspired
by the observation of the 1/2-vortex in high-temperature superconductors made by [J.R. Kirtley, C.C. Tsuei, M. Rupp et al., Phys. Rev. Lett. 76, 1336 (1996)]. The fractional value of the winding number leads to a frac-tional value of the invariant which describes the
topology of the energy spectrum of fermions. This results in the phenomenon of the “half-crossing:” the spectrum approaches
zero but does not cross it, being captured at the zero energy level. The similarity with the phenomenon of fermion condensation
is discussed.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 9, 729–734 (10 May 1996)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
3.
Following our experimental observations of disclination lines in freely suspended droplets and free-standing films (Yu.A.
Nastishin et al., Eur. Phys. J. E 5 353 (2001)), topological defects of the twist grain boundary (TGBA) phase are considered according to two aspects: topological
and energetical. There are two classes of line defects, disclinations (as in the cholesteric (N*) phase and the liquid vortices phase (NL*), relating to the directors tripod symmetries) and dispirations (relating to the translation-rotation symmetries); there are no topological point defects. Differences between N*, NL* and
TGBA disclinations are physical, not topological. The absence of focal conic domains in the TGBA phase is an immediate consequence of the materialization of the helical axis
(along the χ-director); the same feature, coupled to the trend to parallelism of the smectic layers, accounts for the predominance
of λ-lines. Finally, the presence of defects akin to developable domains is explained in the frame of the leastcurvaturemodel, that requires the introduction of a third type of defects: the densitiesofedgedislocations of the smectic layers.
Received 20 February 2002 相似文献
4.
G. E. Volovik 《JETP Letters》1997,65(2):217-223
Vortex mass in Fermi superfluids and superconductors and its influence on quantum tunneling of vortices are discussed. The
vortex mass is essentially enhanced due to the fermion zero modes in the core of the vortex: the bound states of the Bogoliubov
quasiparticles localized in the core. These bound states form the normal component, which is nonzero even in the low-temperature
limit. In the collisionless regime ω
0
τ≫1 the normal component trapped by the vortex is unbound from the normal component in a bulk superfluid/superconductor and
adds to the inertial mass of the moving vortex. In a d-wave superconductor the vortex mass has an additional factor of (B
c2/B)1/2 due to the gap nodes.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 2, 201–206 (25 January 1997)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
5.
A theoretical explanation is given for the “unexpected” behavior recently observed in the radiation spectrum of ultrarelativistic
electrons in a thin layer of matter in an experimental investigation of the Landau-Pomeranchuk-Migdal effect at SLAC [S. R.
Klein et al., Preprint SLAC-6378, Stanford (1993); P. L. Anthony et al., Phys. Rev. Lett. 75, 1949 (1995)].
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 11, 837–840 (10 June 1996) 相似文献
6.
In constructing a theory of thermal diffusiophoresis of volatile aerosol particles it is necessary to have boundary conditions
for the tangential velocity component which allow for the presence of heterogeneous chemical reactions. Conditions of this
sort have been obtained by a number of authors [R. N. Gupta et al., Technical Papers, AIAA 22nd Aerospace Science Meeting, AIAA 19th Thermophysics Conference, New York (1985), pp. 465–490; D. V. Kul’ginov, Tech. Phys. 63, 940 (1993); A. V. Bogdanov et al., Preprint No. 1051, Fiz-Tekh. Inst. Akad. Nauk. SSSR, Leningrad (1986)]. The results of Gupta et al. are in the form of analytical expressions, but their computations actually used Maxwell’s method, which is of low accuracy.
Kul’ginov et al. and Bogdanov et al. used the method of matched asymptotic expansions, which did not permit them to get simple analytical expressions. In the
present paper the slip velocity is calculated by the Loyalka method. Analytical expressions are obtained for the slip coefficients,
and the results of numerical calculations are presented. It is shown that in the presence of concentration gradients of the
components of the gaseous mixture along the surface of an aerosol particle, the slip velocity can acquire new terms due to
the change in the sticking coefficient along the catalytic surface. Expressions in final form are given for these terms.
Zh. Tekh. Fiz. 67, 29–33 (May 1997) 相似文献
7.
Topological media are systems whose properties are protected by topology and thus are robust to deformations of the system.
In topological insulators and superconductors the bulk-surface and bulk-vortex correspondence gives rise to the gapless Weyl,
Dirac or Majorana fermions on the surface of the system and inside vortex cores. Here we show that in gapless topological
media, the bulk-surface and bulk-vortex correspondence is more effective: it produces topologically protected gapless fermions
without dispersion—the fiat band. Fermion zero modes forming the flat band are localized on the surface of topological media
with protected nodal lines [A. P. Schnyder and S. Ryu, Phys. Rev. B 84, 060504(R) (2011); T. T. Heikkil G. E. Volovik, JETP Lett. 93, 59 (2011)] and in the vortex core in systems with topologically protected Fermi points (Weyl points) [G. E. Volovik, JETP
Lett. 93, 66 (2011)]. Flat band has an extremely singular density of states, and we show that this property may give rise in particular
to surface superconductivity which could exist even at room temperature. 相似文献
8.
D. V. Antonov 《JETP Letters》1997,65(9):701-707
The correction to the Hamiltonian of a quark-antiquark system due to the rigidity term in the action of the gluodynamics string
is found using the action obtained by D. V. Antonov et al., Mod. Phys. Lett. A 11, 1905 (1996) with the Hamiltonian obtained by A. Yu. Dubin et al., Phys. At. Nucl. 56, 1745 (1993); Phys. Lett. B 323, 41 (1994) and E. L. Gubankova and A. Yu. Dubin, Phys. Lett. B 334, 180 (1994); preprint ITEP 62-94. This correction contains additional contributions to the orbital momentum of the system
and several higher derivative operators. The resulting Hamiltonian is used to evaluate the rigid-string-induced term in the
Hamiltonian of the relativistic quark model for the case of large masses of the quark and antiquark.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 9, 673–678 (10 May 1997)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
9.
We show that there exists a topological phase equal to π for circular quantum dots with an odd number of electrons. The non-zero
value of the topological phase is explained by axial symmetry and two-dimensionality of the system. Its particular value (π)
is fixed by the Pauli exclusion principle and leads to half-integer values for the eigenvalues of the orbital angular momentum.
Our conclusions agree with the experimental results of T. Schmidt et al., Phys. Rev. B 51, 5570 (1995), which can be considered as the first experimental evidence for the existence of the new topological phase and
half-integer quantization of the orbital angular momentum in a system of an odd number of electrons in circular quantum dots.
The article is published in the original. 相似文献
10.
G. E. Volovik 《JETP Letters》1999,70(9):609-614
The energy levels of fermions bound to the vortex core are considered for the general case of chiral superconductors. There
are two classes of chiral superconductivity: in the class I superconducting state the axisymmetric singly quantized vortex
has the same energy spectrum of bound states as in an s-wave superconductor: E=(n+1/2)ω0, with integral n. In class II the corresponding spectrum is E=nω0 and thus contains a state with exactly zero energy. The effect of a single impurity on the spectrum of bound states is also
considered. For class I the spectrum acquires the doubled period ΔE=2ω0 and consists of two equidistant sets of levels, in accordance with A. I. Larkin and Yu. N. Ovchinnikov, Phys. Rev. B 57, 5457 (1998). For the class II states the spectrum is not influenced by a single impurity if the same approximation is applied.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 9, 601–606 (10 November 1999)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
11.
In a real system the heating is nonuniform, and a second-order phase transition to a broken-symmetry phase occurs by propagation
of a temperature front. Two parameters, the cooling rate τ
Q
and the transition front velocity ν
T
determine the nucleation of topological defects. Depending on the relation of these parameters, two regimes are found: in
the regime of fast propagation defects are created according to the Zurek scenario for the homogeneous case, while in the
slow-propagation regime vortex formation is suppressed.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 1, 96–101 (10 January 1997)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
12.
G. E. Volovik 《JETP Letters》1996,64(11):845-852
Poisson brackets for the Hamiltonian dynamics of vortices are discussed for 3 regimes, in which the dissipation can be neglected
and the vortex dynamics is reversible: (i) The superclean regime, in which the spectral flow is suppressed. (ii) The regime
in which the fermions are pinned by the crystal lattice. This includes the regime of extreme spectral flow of fermions in
the vortex core: these fermions are effectively pinned by the normal component. (iii) The case when the vortices are strongly
pinned by the normal component. All these limits are described by the single parameter C
0, the physical meaning of which is discussed for superconductors containing several bands of electrons and holes. The effect
of the topology of the Fermi surface on the vortex dynamics is also discussed.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 11, 794–800 (10 December 1996)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
13.
V. A. Belyakov 《JETP Letters》1999,70(12):811-818
It has been predicted by Shelton and Shen [Phys. Rev. A 5, 1867 (1972)] and observed by Kajikawa et al. [Jpn. J. Appl. Phys. Lett. 31, L679 (1992)] and Yamada et al. [Appl. Phys. B 60, 485 (1995)] that the efficiency of nonlinear-optical frequency conversion increases significantly in a nonlinear periodic
medium and, accordingly, the intensity of the generated harmonic increases as the fourth power of the sample thickness, as
opposed to the square law observed in homogeneous media. In this paper it is shown that the same enhancement of the efficiency
of nonlinear-optical frequency conversion in a nonlinear periodic medium can be achieved using an ordinary pump wave in the
form of a plane wave when both the pump wave and the harmonics are diffracted by the periodic structure of the nonlinear medium.
The phenomenon is analyzed quantitatively in the example of second-harmonic generation.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 12, 793–799 (25 December 1999) 相似文献
14.
N. A. Inogamov Yu. V. Petrov S. I. Anisimov A. M. Oparin N. V. Shaposhnikov D. von der Linde J. Meyer-ter-Vehn 《JETP Letters》1999,69(4):310-316
Recent experiments have utilizied high-power subpicosecond laser pulses to effect the ultrafast heating of a condensed material
to temperatures far above the critical temperature. Using optical diagnostics it was established that a complicated density
profile with sharp gradients, differing substantially from an ordinary rarefaction wave, forms in the expanding heated matter.
The present letter is devoted to the analysis of the expansion of matter under the conditions of the experiments reported
by D. von der Linde, K. Sokolowski-Tinten, and J. Bialkowski, Appl. Surf. Science 109/110, 1 (1996); K. Sokolowski-Tinten, J. Bialkowski, A. Cavalleri et al., Proc. Soc. Photo-Opt. Instum. Eng. 3343, 46 (1998); and, K. Sokolowski-Tinten, J. Bialkowski, A. Cavalleri et al., Phys. Rev. Lett. 81, 224 (1998). It is shown that if the unloading adiabat passes through the two-phase region, a thin liquid shell filled with
low-density two-phase matter forms in the expanding material. The shell moves with a constant velocity. The velocity in the
two-phase material is a linear function of the coordinate (flow with uniform deformation), and the density is independent
of the coordinate and decreases with time as t
−1.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 4, 284–289 (25 February 1999) 相似文献
15.
Summary In this paper, we compare the carbonate record obtained by us (Cini-Castagnoliet al., Nuovo Cimento C,15 (1992) 547) in the CT85-5 Tyrrhenian deep-sea core with that obtained by Kegwin and Jones (J. Geophys. Res. C,99 (1994) 12397) in the western North Atlantic GPC-9 Bahama core, during the period of climate stage 3 (20–62 ky BP). Both time
series are radiocarbon tested. An overall similarity between the two carbonate profiles is observed. The Tyrrhenian and the
Bahama records show a maximum correlation coefficientr
2=0.6 for a time shift of 900 y, the latter preceding the former. By using the method of superposition of epochs, we show that
the two series display a similar variability on the time scale between 2000 and 5000 y. Periods and phases of the oscillations
agree within experimental errors. We have recently found in CT85-5 the10Be peak discovered in Vostok ice core at about 35 ky BP; so this marker could be searched in GPC-9 in order to synchronize
in absolute way the past ocean conditions. 相似文献
16.
It has recently been claimed that the dynamics
of long-wavelength phason fluctuations has been observed in
i-AlPdMn quasicrystals [S. Francoual et al.
Phys. Rev. Lett. 91, 225501 (2003);
A. Létoublon et al. 54, 753 (2001)]. We will show that
the data reported call for a more detailed development of
the elasticity theory of Jarić and Nelsson [M.V. Jarić and D.R. Nelsson, Phys. Rev. B 37,
4458 (1988)]
in order to determine the nature of small phonon-like atomic displacements
with a symmetry that follows the phason elastic constants.
We also show that a simple model with a single diffusing tile is sufficient
to produce a signal that (1) is situated at a “satellite position”
at a distance q from each Bragg peak; that (2) has an intensity that
scales with the intensity of the corresponding Bragg peak;
(3) falls off as 1/q2; and (4) has a time decay constant that is proportional to 1/Dq2.
It is thus superfluous to call for a picture of “phason waves” in order to explain such data, especially as such “waves” violate
many physical principles. 相似文献
17.
V. V. Ivanov A. V. Kutsenko I. G. Lebo A. A. Matsveiko Yu. A. Mikhailov V. P. Osetrov A. I. Popov V. B. Rozanov G. V. Sklizkov A. N. Starodub V. V. Nikishin V. F. Tishkin 《Journal of Experimental and Theoretical Physics》1999,89(4):689-695
The paper presents results of experiments performed on the Pico facility in which foils were heated by laser radiation, and
anomalously fast burn-through of foils by a structured laser beam was detected. Comparison with two-dimensional calculations
has allowed us to suggest a tentative mechanism for the effect under investigation. The targets in the experiments were thin
aluminum foils of thickness 3 to 40 μm. The flux density of laser radiation on the target surface varied between 1013 and 1014 W/cm2. We detected a strong dependence of the transmitted energy on the foil thickness and the shortening of the transmitted laser
pulse. Penetration of laser radiation through foils with thicknesses considerably larger than 3 μm has been observed, although it was stated in earlier publications [V. V. Ivanov, A. K. Knyazev, A. V. Kutsenko, et al., Kratk. Soobshch. Fiz. FIAN No. 7–8, 37 (1997)]; A. é. Bugrov, I. N. Burdonskii, V. V. Gol’tsov et al., Zh. éksp. Teor. Fiz. 111, 903 (1997) [JETP 84, 903 (1997)] that, at the laser radiation parameters used in our experiment, the evaporated layer of the foil could not be
thicker than 2 μm. Two-dimensional calculations have allowed us to interpret this effect in terms of local “piercing” of the target at spots
on the target surface where the radiation intensity has its peaks. The possibility of reducing these peaks by using a symmetrizing
prepulse is discussed in the paper.
Zh. éksp. Teor. Fiz. 116, 1287–1299 (October 1999) 相似文献
18.
I. M. Dubrovskii 《Journal of Experimental and Theoretical Physics》1997,84(3):525-530
The behavior of a straight Abrikosov vortex in an anisotropic uniaxial London superconductor is studied. Analytical expressions
are derived that approximately describe the magnetic field in three regions: the asymptotic region, where the distance r from the vortex line is greater than λΓ (λ is the London length and Γ is the anisotropy constant), the intermediate region λ<r<λΓ, and the region r<λ. It is found that in the intermediate region with high anisotropy the component of the magnetic field along the vortex line
changes sign for a certain interval of angles between the vortex line and the anisotropy axis. Because of this the interaction
of parallel vortices whose plane is parallel to the anisotropy axis has a minimum and a maximum. This means that numerous
metastable vortex lattices can exist. Additional terms in the vortex self-energy are obtained, and although they are smaller
than the leading logarithmic term, they display a different dependence on the angle between the vortex line and the anisotropy
axis.
Zh. éksp. Teor. Fiz. 111, 954–963 (March 1997) 相似文献
19.
The Cherenkov radiation of generalized Swihart waves is investigated in connection with the slow motion of an Abrikosov-Josephson
vortex, which corresponds to a 2 π kink in the phase difference of Cooper pairs on opposite sides of a tunnel junction. The radiative friction force acting
on such a vortex is determined. An evaluation is made of the steady-state vortex velocity when the accelerating influence
of an electric current through the Josephson junction is compensated by radiative slowing of the vortex due to Cherenkov radiation
from the Abrikosov-Josephson vortex.
Fiz. Tverd. Tela (St. Petersburg) 39, 444–448 (March 1997) 相似文献
20.
E. V. Tkalya 《JETP Letters》1999,70(6):371-374
A new nonradiative decay channel for the anomalously low-lying isomeric level 3/2+ (3.5±1.0 eV) of the 229Th nucleus in a metal via the conduction electrons is examined. The lifetime of the isomer in a metal is calculated. An explanation
is given for the experimental results of S. B. Utter et al., Phys. Rev. Lett. 82, 505 (1999), where the optical radiation spectrum of the indicated isomer was investigated.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 6, 367–370 (25 September 1999) 相似文献