Publications on the project |
018 Locking and unlocking of the counterflow transport in nu=1 quantum Hall bilayers by tilting of magnetic field |
Authors: | D. V. Fil | |
Summary: | The counterflow transport in quantum Hall bilayers provided by superfluid excitons is locked at small input currents due to a complete leakage caused by the interlayer tunneling. We show that the counterflow critical current above which the system unlocks for the counterflow transport can be controlled by a tilt of magnetic field in the plane perpendicular to the current direction. The effect is asymmetric with respect to the tilting
angle. The unlocking is accompanied by switching of the systems from the dc to the ac Josephson state. | |
Keywords: | Quantum Hall bilayer, Josephson vortices, electron-hole pairing | |
Edition: | Phys. Rev. B | | | 2010,
v. 82, pp. 193303-1 - 193303-4,English |
018 Stationary waves in a superfluid exciton gas in quantum Hall bilayers |
Authors: | A. A. Pikalov, D. V. Fil | |
Summary: | Stationary waves in a superfluid magnetoexciton gas in ν = 1 quantum Hall bilayers are considered. The waves are induced by counterpropagating electrical currents that flow in a system with a point obstacle. It is shown that stationary waves can emerge only in imbalanced bilayers in a certain diapason of currents. It is found that the stationary wave pattern is modified
qualitatively under a variation of the ratio of the interlayer istance to the magnetic length d/l. The advantages of using graphene–dielectric–graphene sandwiches for the observation of stationary waves are discussed. We determine the range of parameters (the dielectric constant of the layer that separates two graphene layers and the ratio d/l) for which the state with
superfluid magnetoexcitons can be realized in such sandwiches. | |
Keywords: | | |
Edition: | J. Phys.: Condens. Matt. | | | 2011,
v. 23, p. 265301 (1-9),English |
018 Graphene bilayer structures with superfluid magnetoexcitons |
Authors: | A. A. Pikalov, D. V. Fil | |
Summary: | In this article, we study superfluid behavior of a gas of spatially indirect magnetoexcitons with reference to a
system of two graphene layers embedded in a multilayer dielectric structure. The system is considered as an
alternative of a double quantum well in a GaAs heterostructure. We determine a range of parameters (interlayer
distance, dielectric constant, magnetic field, and gate voltage) where magnetoexciton superfluidity can be
achieved. Temperature of superfluid transition is computed. A reduction of critical parameters caused by impurities
is evaluated and critical impurity concentration is determined. | |
Keywords: | | |
Edition: | Nanoscale Research Letters | | | 2012,
v. 7, p. 145 (1-9),English |
018 Magnetoexciton Superfluidity in Graphene-Dielectric-Graphene Structures. |
Authors: | D. V. Fil, A. A. Pikalov | |
Summary: | Superfluid state of a magnetoexciton gas in bilayers is studied with reference
to graphene-dielectric-graphene structures subjected by a perpendicular to graphene layers
magnetic field B. We find that in difference with quantum Hall bilayers with the total filling
factor ν_T = 1, an imbalance of filling factors of graphene layers is required. An imbalance can be
created by an electrostatic field E applied perpendicular to graphene layers. We determine the
range of B and E where magnetoexciton superfluidity can be realized. The dependence of critical
temperature and critical current on magnetic field is computed. It is found that the maximum
critical temperature is reached at B = 0.5ϕ_0/πd^2, where ϕ_0 is the magnetic flux quantum, and
d is the interlayer distance. It is shown that the interaction of electrons with impurities reduces
the critical temperature. The critical concentration of impurities is determined. Stationary
waves in a superfluid magnetoexciton gas are considered. The waves are induced by counterpropagating
electrical currents that flow in a bilayer with a point obstacle. It is found that the
stationary wave pattern is modified qualitatively under variation of B. | |
Keywords: | | |
Edition: | Journal of Phys.: Conference Series | | | 2012,
v. 400, p. 042006 (1-6).,English |
018 Electron-hole pairing in topological insulator heterostructures in the quantum Hall state |
Authors: | K. V. Germash, D. V. Fil | |
Summary: | Athin film of a topological insulator (TI) on a dielectric substrate and a bulk TI–dielectric film–bulk TI structure
are considered as natural double-well heterostructures suitable for realizing the counterflow superconductivity.
The effect is connected with pairing of electrons and holes belonging to different surfaces of TI and the transition
of a gas of electron-hole pairs into a superfluid state. The case of TI heterostructures subjected to a strong
perpendicular magnetic field is considered. It is shown that such systems are characterized by two critical
temperatures—a mean-field temperature of pairing and a much smaller temperature of the superfluid transition.
The dependence of the critical temperatures on the magnetic field is computed. The advantages of TI based
structures in comparison with GaAs heterostructures as well as graphene based heterostructures are discussed. | |
Keywords: | | |
Edition: | Phys. Rev. B | | | 2013,
v. 87, p.1153139 (2013).,English |
018 Electron-hole pairing and superconductivity in bilayer systems on the base of graphene and topological insulators |
Authors: | D. V. Fil | |
Summary: | Проведенный теоретический анализ показал, что в двухслойных системах на основе графена и топологических изоляторов сверхпроводимость, обусловленная электрон-дырочным спариванием, может проявляться при температурах значительно выше гелиевых. Без использования магнитного поля высокую критическую температуру будут иметь структуры на основе топологических изоляторов и двухслойного графена. Использование квантующего магнитного поля позволяет достичь достаточно высокой критиче-ской температуры в структурах на основе монослойного графена. Перспективы дальнейшего повышения критической температуры связаны с использованием в качестве прослойки между графеновыми слоями материалов с малой диэлек-трической проницаемостью, поиском топологических изоляторов с относитель-но малой диэлектрической проницаемостью и большим значением эффектив-ной постоянной тонкой структуры alpha, а также с синтезом графинов с alpha>4. | |
Keywords: | | |
Edition: | in "Nanosystems and Namonaterials. Investigations in Ukraine. | | | 2014,
99-103,Russian |
018 Diamagnetism and suppression of screening as hallmarks of electron-hole pairing in a double-layer graphene system. |
Authors: | К. V. Germash, D. V. Fil | |
Summary: | We study how the electron-hole pairing reveals itself in the
response of a double layer graphene system to the vector and scalar
potentials. Electron-hole pairing results in a rigid (London)
relation between the current and the difference of vector
potentials in two adjacent layers. The diamagnetic effect can be
observed in multiple connected systems in the magnetic field
parallel to the graphene layers. Such an effect would be considered
as a hallmark of the electron-hole pairing, but the value of the
effect is extremely small. Electron-hole pairing significantly changes
the response to the scalar potential, as well. It
results in a complete (at zero temperature) or partial (at finite
temperature) suppression of screening of the electric field of a
test charge situated at some distance to the double layer system. A
strong increase of the electric field induced by the test charge
under decrease in temperature can be considered as a spectacular
hallmark of the electron-hole pairing. | |
Keywords: | Graphene, electron-hole pairing, screening, diamagnetism | |
Edition: | http://arxiv.org | | | 2014,
1412.5132 , Phys. Rev. B, 2015. v. 91 pp. 115442(1-10) ,English |
The events in the framework of the project |
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018 Executant:Institute for Single Crystals, Department of Physical and Technical Problems of Materials Science, Section Physical, Engineering and Mathematics 1. Physics of nanostructures Purpose: Expected results:Release of new product: material Stage 1: Stage 2: Stage 3: Stage 4: Stage 5:
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