Russian Academy of Sciences

Landau Institute for Theoretical Physics

In Print

Laser technologies: science and applications

15 February in 11:30

N.A. Inogamov

In the first part of report the combined action of laser and plasmonic electromagnetic fields which dissipate in a metal film is considered. Fast dissipation of energy of light causes mechanical response moving a film. Motion and subsequent fast re-crystallization result in formation of surface micro-structures used for holographic purposes [1,2]. In the second part the physics of laser fragmentation of a liquid tin micro-droplet is analyzed. This is important for development of next generation of photo-lithography machines [3]. In the third part the indirect monitoring shot-to-shot shock waves strength reproducibility during the pump-probe experiments is studied [4]. The calibrated laser source is used after this checking for generation of shocks; goals for employing of these shocks are described in Albertazzi et al., Science Advances, 3(6), e1602705 (2017). [1] J. Phys.: Conf. Ser., 1092, 012051 (2018) [2] J. Phys.: Conf. Ser., 1092, 012052 (2018) [3] Phys. Rev. Applied 10, 064009 (2018) [4] J. Appl. Phys. 120, 035901 (2016)

Shock generation by laser and impact initiation of burning

15 February in 11:30

N.A. Inogamov

Generation of shocks by an ultrashort laser pulse is considered. Elastic-plastic response and polymorphic alpha-epsilon transition in iron are analyzed [1,2]. Initiation of initial stages of burning of high explosives by slow impact is studied [3]. Burning is caused by dissipative heating during plastic deformations.
[1] S.I. Ashitkov, V.V. Zhakhovsky, N.A. Inogamov, P.S. Komarov, M.B.Agranat, and G.I.Kanel, The behavior of iron under ultrafast shock loading driven by a femtosecond laser, AIP Conf. Proc. 1793, 100035 (2017) [2] V.V. Zhakhovsky, K.P. Migdal, N.A. Inogamov, S.I. Anisimov, MD simulation of steady shock-wave fronts with phase transition in single-crystal iron, AIP Conf. Proc. 1793, 070003 (2017) [3] D. Ilnitsky, N. Inogamov, V. Zhakhovsky, Response of explosive HMX to low-velocity impact: Modeling by the crystal plasticity finite element method, J. Phys.: Conf. Ser., 941, 012052 (2018)

Three-dimensional numerical simulation of long-lived quantum vortex knots and links in a trapped Bose-Einstein condensate

8 February in 11:30 (short)

V.P. Ruban

Dynamics of simplest vortex knots, unknots, and links of torus type inside an atomic Bose-Einstein condensate in anisotropic harmonic trap at zero temperature has been numerically simulated using three-dimensional Gross-Pitaevskii equation. The lifetime for such quasi-stationary rotating vortex structures has been found quite long in wide parametric domains of the system. This result is in qualitative agreement with a previous prediction based on a simplified one-dimensional model approximately describing dynamics of vortex filaments.

CALCULATION OF THE DISCRETE SPECTRUM OF SOME TWO-DIMENSIONAL SCHR¨ODINGER EQUATIONS WITH A MAGNETIC FIELD

8 February in 11:30

V.G. Marikhin, A.V. Marikhina

One of us previously obtained and integrated the first examples of two-dimensional Schr¨odinger equations with a magnetic field belonging to the class of quasi–exactly solvable problems. It was shown that the wave functions are expressed in terms of degenerations of the Heun function: biconfluent and confluent Heun functions. Algebraic conditions were also found that determine the discrete spectrum and wave functions. Our goal here is to solve these algebraic equations numerically. In some cases, we can find an analytic approximation of the discrete spectrum.

Hermite quasi-polynomials

8 February in 11:30 (short)

V.G. Marikhin

The Hermite quasi-polynomials are obtained (the square root of the weight coincides with the Hermite one). The corresponding spectral problem with singularity at zero is constructed. The space to which belong the eigenfunctions of the above-mentioned spectral problem is constructed. The kind of this space solves the paradox with singularity.

Perkolyatsiya i dzhamming obraztsov sluchainoi posledovatel’noi adsorbtsii dlinnykh k-merov na kvadratnoi reshetke

8 February in 11:30 (short)

L.Yu. Barash

Pri pomoshchi komp’yuternogo modelirovaniya izuchayutsya perkolyatsionnyi perekhod i sostoyanie dzhamminga v modeli izotropnoi sluchainoi posledovatel’noi adsorbtsii. Razrabotan parallel’nyi algoritm, kotoryi ochen’ effektiven s tochki zreniya ego skorosti i ispol’zovaniya pamyati, i primenen k modeli sluchainoi posledovatel’noi adsorbtsii dlinnykh k-merov na kvadratnoi reshetke s periodicheskimi granichnymi usloviyami. Vychisleny porogovye plotnosti perkolyatsii i dzhamminga dlya dlin k-merov vplot’ do 131072. Ranee v literature takie vychisleniya provodilis’ tol’ko dlya k ≤ 512. Naiden rezhim povedeniya perkolyatsionnoi plotnosti dlya bol’shikh dlin chastits. Proanalizirovana struktura perkolyatsionnogo i dzhammingovogo sostoyanii. Teoreticheskie rezul’taty raboty [G. Kondrat et al., Phys. Rev. E 022154, 2017] obobshcheny na sluchai periodicheskikh granichnykh uslovii. Dokazano, chto lyuboi klaster v sostoyanii dzhamminga yavlyaetsya perkolyatsionnym klasterom, i chto perkolyatsiya voznikaet do dzhamminga.
Soobshchenie po rezul’tatam raboty M.G. Slutskii, L.Yu. Barash, Yu.Yu. Tarasevich, Percolation and jamming of random sequential adsorption samples of large linear k-mers on a square lattice, Phys. Rev. E 98, 062130 (2018).

On complex angular diagrams of magnetic conductivity in strong magnetic fields

1 February in 11:30 (short)

A.Ya. Maltsev

We consider angular conductivity diagrams for normal (single-crystal) metals with complex Fermi surfaces in the presence of strong magnetic fields. The behavior of conductivity in this case strongly depends on the direction of the magnetic field and the stable nontrivial regimes of this behavior correspond to special zones of stability on the angular diagram corresponding to certain (topological) properties of the conductivity tensor. As we show, in the general case such diagrams can be divided into two general types, simple (type A) and complex (type B). We will be interested in the diagrams of the second type, which have a number of specific features (an infinite number of stability zones, the presence of chaotic regimes, etc.), which we will consider in more detail.

Obshchie osobennosti uglovykh diagramm provodimosti metallov v sil’nykh magnitnykh polyakh.

1 February in 11:30 (short)

A.Ya. Mal’tsev

My rassmotrim samye obshchie osobennosti uglovykh diagramm provodimosti v normal’nykh metallakh so slozhnymi poverkhnostyami Fermi v prisutstvii sil’nykh magnitnykh polei. Opisanie takikh osobennostei budet osnovano na topologicheskom opisanii dinamicheskoi sistemy, voznikayushchei dlya evolyutsii elektronnykh sostoyanii na poverkhnosti Fermi v prisutstvii vneshnego magnitnogo polya.
Po rezul’tatam rabot: ZhETF, t. 151, vyp. 5, 944-973 (2017); ZhETF, t. 152, vyp. 5(11), 1053-1064 (2017)

JKLMR conjecture and Batyrev construction

1 February in 11:30

A. Belavin, A. Aleshkin, A. Litvinov

JKLMR gipoteza predpolagaet svyaz’ mezhdu tochnoi vychislennoi statsummoi nekotoroi Kalibrovochnoi supersimmetrichnoi Sigma-model’yu Vittena i Geometriei na prostranstve polei effektivnoi teorii polya, voznikayushchei v teorii Superstrun, kompaktifitsirovannoi na mnogoobrazie Kalabi-Yao. Ya rasskazhu o tom, kak ispol’zuya dual’nost’ mezhdu mnogrannikami Batyreva, ustanovit’ vysheukazannoe sootvetstvie tochno.
arXiv:1812.00478, submitted to Journal Statistical Physics

Ergodicheskie svoistva dinamicheskikh sistem na dvumernykh poverkhnostyakh i elektronnye transportnye yavleniya v normal’nykh metallakh

1 February in 11:30 (short)

A.Ya. Mal’tsev, S.P. Novikov

V doklade obsuzhdaetsya svyaz’ spetsial’nykh kharakteristik dinamicheskikh sistem na poverkhnostyakh (indeksov Zoricha - Kontsevicha - Forni) s povedeniem provodimosti v metallakh v sil’nykh magnitnykh polyakh. Dannoe rassmotrenie yavlyaetsya vazhnym v sluchae vozniknoveniya naibolee slozhnykh (khaoticheskikh) elektronnykh traektorii na poverkhnosti Fermi, vozmozhnom dlya dostatochno slozhnykh poverkhnostei i spetsial’nykh napravlenii magnitnogo polya. Kak mozhno pokazat’, upomyanutye kharakteristiki imeyut neposredstvennoe otnoshenie k povedeniyu magnitoprovodimosti, takim obrazom, mozhno v printsipe govorit’ o vozmozhnosti ikh eksperimental’nogo opredeleniya v sootvetstvuyushchikh sluchayakh.

1 February in 11:30


Pretsessiya spina zaryazhennoi chastitsy s MDM i EDM v gravitatsionnom pole Zemli

25 January in 11:30 (short)

S.N. Vergeles, N.N. Nikolaev

Vychislena uglovaya skorost’ pretsessii spina zaryazhennoi chastitsy s MDM i EDM v gravitatsionnom pole Zemli s uchyotom sutochnogo vrashcheniya. Khotya bol’shaya chast’ rezul’tata yavlyaetsya klassicheskoi i khorosho izvestnoi, vklad v pretsessiyu ot sutochnogo vrashcheniya do sikh por yavlyaetsya diskussionnym. Korrektnyi uchyot etogo vklada predstavlyaetsya neobkhodimym, tak kak eto vliyaet na pravil’nuyu traktovku eksperimentov po pretsessii spina v uskoritelyakh.

Generirovanie effektivnoi fermionnoi vershiny gravitatsionnym instantonom v reshetochnoi teorii gravitatsii

25 January in 11:30 (short)

S.N. Vergeles

Pokazano, chto v reshetochnoi gravitatsii, svyazannoi s fermionami, voznikayut effektivnye fermionnye vershiny. Eti vershiny generiruyutsya gravitatsionnymi instantonami, analogichno tomu kak voznikayut effektivnye fermionnye vershiny v teorii Yanga-Millsa vsledstvie nalichiya fermionnykh nulevykh mod, svyazannykh s instantonami.

Collinear photon emission from the quark-gluon plasma in heavy ion collisions

25 January in 11:30

B.G. Zakharov

Making use the light-cone path integral scheme we develop a formalism for collinear photon emission from the quark-gluon plasma (QGP) that accounts for accurately the Landau-Pomeranchuk-Migdal effect. In the case of the QGP without magnetic field we reproduce the AMY (Arnold, Moore, Yaffe (2001)) photon spectrum obtained within the thermal field theory. In the first part of the talk we study the role of running coupling and the effect of variation of the thermal quark mass on contribution of the collinear bremsstrahlung and quark-antiquark annihilation to photon emission in AA collisions in a scheme similar to that used in our previous jet quenching analyses. We find that for a scenario with the thermal quark mass about 50-100 MeV contribution of the higher order collinear processes summed with the 2 \to 2 processes can explain a considerable part (about 50%) of the experimental photon spectrum at k_T about 2-3 GeV for Au+Au collisions at $\sqrt{s}=0.2$ TeV. But for quark mass 300 MeV and for the thermal quark mass predicted by the hard thermal loop scheme the theoretical predictions underestimate considerably the experimental spectrum. In the second part of the talk we discuss a generalization of our formalism to the QGP with magnetic field. We then use it to investigate the effect of magnetic field on the photon emission from the QGP created in AA collisions. We find that even for very optimistic assumption on the magnitude of the magnetic field generated in AA collisions its effect on the photon emission rate is practically negligible. For this reason the magnetic field cannot generate a significant azimuthal asymmetry in the photon spectrum as it was suggested in the analysis by Tuchin (K. Tuchin, Phys. Rev. C{\bf 91}, 014902 (2015)).

Recent applications of the light-cone path integral formalism to the radiative effects in $AA$-collisions due to the induced gluon/photon emission in the QCD matter

18 January in 11:30

B.G. Zakharov

In this talk I discuss some recent applications of the light-cone path integral (LCPI) approach to the induced gluon/photon emission in the quark-gluon plasma (QGP) in $AA$-collisions at RHIC-LHC energies. I start with a brief discussion of the basic formulas of the LCPI formalism. Then I present the results for the nuclear modification of the photon-tagged jets in $AA$ collisions within the jet quenching scheme based on the LCPI approach to the induced gluon emission. The calculations are performed for running coupling. Collisional energy loss is treated as a perturbation to the radiative mechanism. We obtain a reasonable agreement with the recent data from the STAR Collaboration on the mid-rapidity nuclear modification factor $I_{AA}$ for Au+Au collisions at $\sqrt{s}=200$ GeV for parametrization of running $\alpha_s$ consistent with that necessary for description of the data on suppression of the high-$p_T$ spectra. The main part of the talk will be devoted to the radiative contribution to the jet $p_T$-broadening in the QGP. For the first time the analysis of the radiative $p_T$-broadening of a fast quark in the QGP is performed accounting for the real and virtual two-parton states beyond the soft gluon approximation. It is shown that radiative processes can strongly suppress the radiative $p_T$-broadening in the QCD matter (and even make it negative). This prediction is qualitatively different from the results of previous analyses in th soft gluon approximation in the double logarithmic approximation (B. Wu, JHEP 1110, 029 (2011); T. Liou, A. H. Mueller and B. Wu, Nucl. Phys. A916, 102 (2013); J.-P. Blaizot and Y. Mehtar-Tani, Nucl. Phys. A929, 202 (2014)) predicting that radiative processes should significantly increase $p_T$-broadening. Our prediction is consistent with the recent data of the STAR Collaboration (L. Adamczyk et al., Phys.Rev. C96, 024905 (2017)), which do not show any signal of $p_T$-broadening in Au+Au collisions at the energy 200 GeV. At the end of the talk I discuss the the role of running coupling and the effect of variation of the thermal quark mass on contribution of the collinear bremsstrahlung and annihilation to photon emission in $AA$ collisions in a scheme similar to that used in our previous jet quenching analyses.

Inelastic neutron scattering as a confirmation of a new type of gapped surface excitations in liquid helium

18 January in 11:30 (short)

P.D. Grigoriev, A.D. Grigoriev, A.M. Dyugaev

We analyze the experimental data on inelastic neutron scattering by a thin ~5-atomic-layer film of liquid helium at three different temperatures: T=0.4K, 0.98K and 1.3K. The neutron scattering intensity plots, in addition to the previously know dispersion of phonons and ripplons, suggest a branch of gapped surface excitations with activation energy ~4.5K and the dispersion similar to that expected for surfons -- the bound quantum states of helium atoms above liquid helium surface, proposed and investigated theoretically. These data, probably, provide the first direct experimental confirmation of surfons. Before these surface excitations received only indirect experimental substantiation, based on the temperature dependence of surface tension coefficient and on their interaction with surface electrons. The existence of surfons as an additional type of surface excitations, although being debated yet, is very important for various physical properties of He surface. We also analyze previous numerical results on excitations in liquid helium and argue that surface excitations similar to surfons have been previously obtained by numerical calculations and called resonance interface states.

Linear magnetoresistance in the charge density wave state of quasi-two-dimensional rare-earth tritellurides

18 January in 11:30 (short)

P.D. Grigoriev

The magnetoresistance of a TbTe3 two-dimensional conductor with a charge-density wave (CDW) has been measured in a wide temperature range and in magnetic fields of up to 17 T. At temperatures well below the Peierls transition temperature and in high magnetic fields, the magnetoresistance exhibits a linear dependence on the magnetic field caused by the scattering of normal charge carriers by “hot” spots of the Fermi surface. In the sliding CDW regime in low magnetic fields, a qualitative change in the magnetoresistance has been observed associated with the strong scattering of carriers by the sliding CDW.
[1] A.V. Frolov, A.P. Orlov, P.D. Grigoriev, V.N. Zverev, A.A. Sinchenko, P. Monceau, Magnetoresistance of a Two-Dimensional TbTe3 Conductor in the Sliding Charge-Density Wave Regime, JETP Lett., 107(8), 488-492 (2018)

Dual description of integrable sigma-models

11 January in 11:30

Litvinov Alexey

In my talk I will discuss an example of the weak / strong coupling duality, i.e. equivalence seemingly distinct quantum field theories, so that the strong coupling regime of one theory describes the weak coupling regime of the other, and vice versa. In my example, these are two-dimensional sigma models and boson field theories with exponential interaction. Both theories are integrable. To explain the duality, I will construct a W-algebra commuting with a set of screening operators on one side and solve the Ricci flow equation with given ultraviolet asymptotic boundary conditions.
The report is based joint work with Fateev and Spodyneiko.

Deautonomization of cluster integrable systems

11 January in 11:30

M. Bershtein

Cluster integrable systems have a combinatorial definition in terms of counting dimer configurations on a bipartite graph on a torus. They have a large group of discrete symmetries preserving the Hamiltonian. After deautonomization, the Hamiltonians depend on time, integrability disappears, and discrete symmetry leads to remarkable difference equations, such as the Painleve equations. These equations are solved using the partition functions of five-dimensional supersymmetric theories. The talk is based on joint work with P. Gavrilenko and A. Marshakov.

Elektronnye svoistva neuporyadochenogo grafena

28 December 2018 in 11:30

Pavel Ostrovskii

Doklad po predstavlyaemoi k zashchite doktorskoi dissertatsii.

On the initial conditions in heavy ion collisions at RHIC and LHC energies

21 December 2018 in 11:30 (short)

B.G. Zakharov

We discuss our recent results on the heavy ion collisions at RHIC and LHC energies. We discuss the initial conditions for the entropy distribution in AA-collisions within the Glauber Monte-Carlo model accounting for the effect of the meson-baryon components in the nucleon light-cone wave function. Also, we discuss fluctuations of the electromagnetic fields produced in the non-central AA-collisions in the classical and quantum picture. We show that quantum calculations based on the fluctuation-dissipation theorem give fluctuations of the electromagnetic field that are much smaller than that in the classical Monte-Carlo calculations with the Woods-Saxon nuclear density widely used in the literature.

Quantum corrections to conductivity of disordered electrons due to inelastic scattering off magnetic impurities

21 December 2018 in 11:30

I.S. Burmistrov

We study the quantum corrections to the conductivity of the two-dimensional disordered interacting electron system in the diffusive regime due to inelastic scattering off rare magnetic impurities. We focus on the case of very different g factors for electrons and magnetic impurities. Within the Born approximation for the inelastic scattering off magnetic impurities we find additional temperature-dependent corrections to the conductivity of the Altshuler-Aronov type.
The talk is based on I. S. Burmistrov and E. V. Repin, Phys. Rev. B 98, 045414 (2018)

Magnetism of Bi2Se3 thin films with Eu-rich flat inclusions

21 December 2018 in 11:30 (short)

I.S. Burmistrov

I report about theoretical support of experimental data on the measurement of the magnetic properties of thin films of bismuth selenide doped with europium atoms, which form flat inclusions. The magnitudes of the various mechanisms of magnetic ordering are theoretically estimated. The estimates obtained are in satisfactory agreement with the experimental data.
Report is based on the paper: L.N. Oveshnikov, Ya.I. Rodionov, K.I. Kugel, I.A. Karateev, A.L. Vasiliev, Yu.G. Selivanov, E.G. Chizhevskii, I.S. Burmistrov and B.A. Aronzon, "Magnetism of Bi2Se3 Thin Films with Eu-rich flat inclusions", J. Phys .: Condens. Matter 30, 445801 (2018)

Volterra chain and Catalan numbers

21 December 2018 in 11:30 (short)

V.E. Adler, A.B. Shabat

The model problem on the decay of a step for the Volterra chain is formulated as a Cauchy problem with initial condition equal to 0 in one node and 1 in the others. We show that this problem admits an exact solution in terms of the Bessel functions. The Taylor series arising here are related to the exponential generating function for Catalan numbers. Asymptotic formulas for the solution are obtained.

Two-sphere partition functions and Kahler potentials on CY moduli spaces

14 December 2018 in 11:30 (short)

A. Belavin, K. Aleshkin, A. Litvinov

We study the relation between exact partition functions of gauged $N=(2,2)$ linear sigma-models on $S^{2}$ and K\"ahler potentials of CY manifolds proposed by Jockers et all. We suggest to use a mirror version of this relation. For a class of manifolds given by a Fermat hypersurfaces in weighted projective space we check the relation by explicit calculation.
Aleshkin K., Belavin A., Litvinov A., “Two-sphere partition functions and Kähler potentials on CY moduli spaces”, Письма в ЖЭТФ, 108(10), 725 (2018)

Probing spin susceptibility of a correlated two-dimensional electron system by transport and magnetization measurements

14 December 2018 in 11:30 (short)

I.S. Burmistrov

I report theoretical support of the data on measuring the spin susceptibility at different temperatures and electron concentrations in a two-dimensional electron system based on a silicon field-effect transistor in the group of V.M. Pudalov (Lebedev Institute).
The short talk is based on the work of V. M. Pudalov, A. Yu. Kuntsevich, M.E. Gershenson, I.S. Burmistrov, and M. Reznikov, Phys. Rev. B 98, 155109 (2018).

A thermally driven spin-transfer-torque system far from equilibrium: enhancement of the thermoelectric current via pumping current

14 December 2018 in 11:30

I.S. Burmistrov

We consider a small itinerant ferromagnet exposed to an external magnetic field and strongly driven by a thermally induced spin current. For this model, we derive the quasi-classical equations of motion for the magnetization where the effects of a dynamical non-equilibrium distribution function are taken into account self-consistently. We obtain the Landau-Lifshitz-Gilbert equation supplemented by a spin-transfer torque term of Slonczewski form. We identify a regime of persistent precessions in which we find an enhancement of the thermoelectric current by the pumping current.
The talk is based on T. Ludwig, I.S. Burmistrov, Y. Gefen, A. Shnirman, "A thermally driven spin-transfer-torque system far from equilibrium: enhancement of the thermoelectric current via pumping current", arxiv:1808.01192

Mesoscopic supercurrent fluctuations in diffusive magnetic Josephson junctions

23 November 2018 in 11:30

P. A. Ioselevich, P. M. Ostrovsky, Ya. V. Fominov

We study the supercurrent in quasi-one-dimensional Josephson junctions with a weak link involving magnetism, either via magnetic impurities or via ferromagnetism. In the case of weak links longer than the magnetic pair-breaking length, the Josephson effect is dominated by mesoscopic fluctuations. We establish the supercurrent-phase relation (CPR) along with statistics of its sample-dependent properties in junctions with transparent contacts between leads and link. High transparency gives rise to the inverse proximity effect, while the direct proximity effect is suppressed by magnetism in the link. We find that all harmonics are present in the CPR. Each harmonic has its own sample-dependent amplitude and phase shift with no correlation between different harmonics. Depending on the type of magnetic weak link, the system can realize a \varphi_0 or \varphi junction in the fluctuational regime. Full supercurrent statistics is obtained at arbitrary relation between temperature, superconducting gap, and the Thouless energy of the weak link.

Statistics of eigenstates near the localization transition on random regular graphs

23 November 2018 in 11:30

Konstantin Tikhonov

Dynamical and spatial correlations of eigenfunctions as well as energy level correlations in the Anderson model on random regular graphs (RRG) are studied. We consider the critical point of the Anderson transition and the delocalized phase. In the delocalized phase near the transition point, the observables show a broad critical regime for system sizes below the correlation volume and then cross over to the ergodic behavior. Eigenstate correlations allow us to visualize the correlation length that controls the finite-size scaling near the transition. The critical-to-ergodic crossover is very peculiar, since the critical point is similar to the localized phase, whereas the ergodic regime is characterized by very fast diffusion which is similar to the ballistic transport. In particular, the return probability crosses over from a logarithmically slow variation with time in the critical regime to an exponentially fast decay in the ergodic regime. We find a perfect agreement between results of exact diagonalization and those resulting from the solution of the self-consistency equation obtained within the saddle-point analysis of the effective supersymmetric action. We show that the RRG model can be viewed as an intricate limit of the Anderson model in spatial dimensions.

Poverkhnostnyi impedans na diffuznoi granitse kiral’nogo p-volnovogo sverkhprovodnika

16 November 2018 in 11:30

Ya.V. Fominov

Vychislena lokal’naya kompleksnaya provodimost’ i obuslovlennyi eyu poverkhnostnyi impedans na diffuznoi granitse kiral’nogo p-volnovogo sverkhprovodnika. Imenno kiral’noe p-volnovoe sostoyanie schitaetsya naibolee veroyatnym v sverkhprovodyashchem rutenate strontsiya Sr2RuO4. Ono anizotropnoe i pri etom polnost’yu shchelevoe (modul’ parametra poryadka fiksirovan, a faza zavisit ot napravleniya). My rassmatrivaem otklik na vneshnee elektromagnitnoe pole kak na podshchelevykh, tak i na nadshchelevykh chastotakh. Izucheny anomal’nye osobennosti poverkhnostnogo impedansa, svyazannye s generatsiei vblizi granitsy nechyotnykh po chastote sverkhprovodyashchikh korrelyatsii (sostoyanie tipa sverkhprovodimosti Berezinskogo). Teoreticheskie rezul’taty sopostavleny s izmereniyami poverkhnostnogo impedansa Sr2RuO4, provedyonnymi v IFTT. Nablyudaetsya kachestvennoe soglasie teorii i eksperimenta.
Doklad osnovan na rabote S. V. Bakurskiy, Ya. V. Fominov, A. F. Shevchun, Y. Asano, Y. Tanaka, M. Yu. Kupriyanov, A. A. Golubov, M. R. Trunin, H. Kashiwaya, S. Kashiwaya, and Y. Maeno, "Local impedance on a rough surface of a chiral p-wave superconductor", Phys. Rev. B 98, 134508 (2018); https://arxiv.org/pdf/1807.11735.pdf

Sverkhprovodyashchii spinovyi klapan v sistemakh so splavom Geislera

16 November 2018 in 11:30 (short)

Ya.V. Fominov

Provedeno teoreticheskoe soprovozhdenie eksperimentov po izmereniyu effekta sverkhprovodyashchego spinovogo klapana v sisteme tipa FFS (gde F — ferromagnetik, S — sverkhprovodnik). Effekt sostoit v tom, chto kriticheskaya temperatura Tc sistemy zavisit ot vzaimnoi orientatsii namagnichennostei dvukh ferromagnetikov. V eksperimente v kachestve srednego F sloya byl vzyat splav Geislera Co2Cr1-xFexAl, i eto pozvolilo usilit’ effekt (raznost’ Tc pri parallel’noi i antiparallel’noi orientatsii) po sravneniyu s ranee issledovannymi sistemami s zhelezom. Znak effekta zavisit ot tolshchiny sloya. Teoriya ob’yasnyaet poluchennye rezul’taty. Usilenie effekta okazyvaetsya svyazano s umen’shennoi velichinoi obmennogo polya v splave Geislera.
Doklad osnovan na sleduyushchikh rabotakh:
[1] A. Kamashev, A. Validov, N. Garif’yanov, Ya. Fominov, P. Leksin, J. Schumann, J. Thomas, V. Kataev, B. Büchner, I. Garifullin, "Isolation of proximity-induced triplet pairing channel in a superconductor/ferromagnet spin valve", EPJ Web of Conferences 185, 08001 (2018).
[2] A.A. Kamashev, A.A. Validov, J. Schumann, V. Kataev, B. Büchner, Ya.V. Fominov, I.A. Garifullin, "Increasing the performance of a superconducting spin valve using a Heusler alloy", Beilstein J. Nanotechnol. 9, 1764 (2018).

New integrals of motion for waves on the deep water with a free surface

16 November 2018 in 11:30 (short)

A.I. Dyachenko

Khorosho izvestno, chto v priblizhenii slaboi nelineinosti dlya voln na vode (teoriya slaboi turbulentnosti), kogda uchityvayutsya tol’ko chetyrekh-volnovye vzaimodeistviya, imeetsya integral dvizheniya - polnoe "chislo voln" (volnovoe deistvie). Volny na glubokoi vode mogut byt’ razdeleny na dve gruppy, begushchie vlevo i begushchie vpravo. Pokazano, chto osobye svoistva koeffitsienta chetyrekh-volnovogo vzaimodeistviya privodyat k sokhraneniyu ne tol’ko polnogo "chisla voln", no i dvukh novykh integralov dvizheniya: "chislo voln", begushchikh vlevo, i "chislo voln", begushchikh vpravo.

Non-Born effects in scattering of electrons in clean quasi-one-dimensional conductors

26 October 2018 in 11:30

A. S. Ioselevich, N. S. Peshcherenko

Quasi-one-dimensional systems demonstrate Van Hove singularities in the density of states $\nu_F$ and the resistivity $\rho$, occurring when the Fermi level $E$ crosses a bottom $E_N$ of some subband of transverse quantization. We demonstrate that the character of smearing of the singularities crucially depends on the concentration of impurities. There is a crossover concentration $n_c\propto |\lambda|$, $\lambda\ll 1$ being the dimensionless amplitude of scattering. For $n\gg n_c$ the singularities are simply rounded at $\varepsilon\equiv E-E_N\sim \tau^{-1}$ – the Born scattering rate. For $n\ll n_c$ the non-Born effects in scattering become essential, despite $\lambda\ll 1$. The peak of the resistivity is split: for $\varepsilon>0$ there is a broad maximum at $\varepsilon\propto \lambda^2$. For $\varepsilon\lt 0$ there is a deep minimum at $|\varepsilon|\propto n^2\ll \lambda^2$. The behaviour of $\rho$ below the minimum depends on the sign of $\lambda$. In case of repulsion $\rho$ monotonically grows with $|\varepsilon|$ and saturates for $|\varepsilon| \gg \lambda^2$. In case of attraction $\rho$ has sharp maximum at $|\varepsilon| \propto \lambda^2$. The latter feature is due to resonant scattering by quasistationary bound states that inevitably arise just below the bottom of each subband for any attracting impurity.

Electron-phonon cooling power in Anderson insulators

26 October 2018 in 11:30

M. V. Feigel'man, V. E. Kravtsov

A theory for electron-phonon energy exchange in Anderson insulators with long localization length is developed. The major contribution to the cooling power as a function of electron temperature is shown to be directly related to the correlation function of the local density of electron states, which is enhanced near the localization transition by multi-fractality and by the presence of Mott's resonant pairs of states. The theory we develop explains huge enhancement of the cooling power observed in insulating Indium Oxide films as compared to predictions of standard theory for disordered metals