arXiv subjects

Ivan A. Shelykh

Publications and source records attributed to Ivan A. Shelykh.

31 records · Page 2Linked to original sources

arXiv2019

Spin-orbit coupled polariton condensates in a radially-periodic potential: Multiring vortices and rotating solitons

We address evolution of a spinor polariton condensate in radially periodic potentials. Such potentials allow for the observation of novel nonlinear excitations and support a variety of dynamically stable soliton states never demonstrated before in polariton condensates, including ring-like solitons with density peaks located in different radial minima of the potential and extended dynamically stable multiring patterns. Among the advantages of the system is that azimuthal modulational instabilities are suppressed due to dominating repulsive interactions between polaritons with the same spin, thereby allowing for the stabilization of radially-symmetric states. The representative feature of this system is that spin-orbit coupling between different spinor components requires them to carry different topological charges. Radially-symmetric states carrying different combinations of topological charges are discussed. Radially symmetric potentials also support stable rotating multipeaked solitons, whose properties unexpectedly depend not only on the magnitude of the rotation velocity, but also on its sign, i.e., on the rotation direction. The latter property is a consequence of spin-orbit coupling which breaks the equivalence between clockwise and counterclockwise rotations. The multiring structures are shown to be robust against unavoidable losses and are therefore amenable to observations with the presently available experimental techniques.

cond-mat.mes-hall↗

arXiv2019

Optical valleytronics in gapped graphene

We propose a scheme to trap and filter electrons, valley dependently, on a scale beyond the diffraction limit, in a gapped Dirac system using a circularly polarized light beam and a microscale metallic resonator. The main mechanism allowing the selection is the valley dependent break of the time reversal symmetry. Indeed in one valley, the light partially closes the already existing gap while it opens it in the other one. This difference in the band structure close to the Dirac points, induces a change in the dynamics of the electrons, leading to a valley router behaviour of the system.

cond-mat.mes-hall↗

arXiv2018

Impact of high-frequency pumping on anomalous finite-size effects in three-dimensional topological insulators

Lowering of the thickness of a thin-film three-dimensional topological insulator down to a few nanometers results in the gap opening in the spectrum of topologically protected two-dimensional surface states. This phenomenon, which is referred to as the anomalous finite-size effect, originates from hybridization between the states propagating along the opposite boundaries. In this work, we consider a bismuth-based topological insulator and show how the coupling to an intense high-frequency linearly polarized pumping can further be used to manipulate the value of a gap. We address this effect within recently proposed Brillouin-Wigner perturbation theory that allows us to map a time-dependent problem into a stationary one. Our analysis reveals that both the gap and the components of the group velocity of the surface states can be tuned in a controllable fashion by adjusting the intensity of the driving field within an experimentally accessible range and demonstrate the effect of light-induced band inversion in the spectrum of the surface states for high enough values of the pump.

cond-mat.mes-hall↗

arXiv2017

Parity solitons in nonresonantly driven-dissipative condensate channels

We study analytically and numerically the condensation of a driven-dissipative exciton-polariton system using symmetric nonresonant pumping geometries. We show that the lowest condensation threshold solution carries a definite parity as a consequence of the symmetric excitation profile. At higher pump intensities competition between the two parities can result in critical quenching of one and saturation of the other. Using long pump channels, we show that the competition of the condensate parities gives rise to a different type of topologically stable defect propagating indefinitely along the condensate. The defects display repulsive interactions and are characterized by a sustained wavepacket carrying a pair of opposite parity domain walls in the condensate channel.

cond-mat.quant-gas↗

arXiv2017

Optical trapping of electrons in graphene

We propose an experimentally friendly scheme for trapping quasi- relativistic elec- trons in graphene by an electromagnetic beam with circular polarization and spatially inhomogeneous profile with an intensity dip. The trapping is achieved due to the ef- fect of bandgap opening outside the trapping region. The proposed mechanism allows for non- invasive electron confinement in graphene without any need of the chemical patterning of the sample or the application of metallic gates.

cond-mat.mes-hall↗

arXiv2017

Exploring nonlinear topological states of matter with exciton-polaritons: Edge solitons in kagome lattice

Matter in nontrivial topological phase possesses unique properties, such as support of unidirectional edge modes on its interface. It is the existence of such modes which is responsible for the wonderful properties of a topological insulator -- material which is insulating in the bulk but conducting on its surface, along with many of its recently proposed photonic and polaritonic analogues. We show that exciton-polariton fluid in a nontrivial topological phase in kagome lattice, supports nonlinear excitations in the form of solitons built up from wavepackets of topological edge modes -- topological edge solitons. Our theoretical and numerical results indicate the appearance of bright, dark and grey solitons dwelling in the vicinity of the boundary of a lattice strip. In a parabolic region of the dispersion the solitons can be described by envelope functions satisfying the nonlinear Schrödinger equation. Upon collision, multiple topological edge solitons emerge undistorted, which proves them to be true solitons as opposed to solitary waves for which such requirement is waived. Importantly, kagome lattice supports topological edge mode with zero group velocity unlike other types of truncated lattices. This gives a finer control over soliton velocity which can take both positive and negative values depending on the choice of forming it topological edge modes.

cond-mat.mes-hall↗

arXiv2017

Hybrid surface waves in two-dimensional Rashba-Dresselhaus materials

We address the electromagnetic properties of two-dimensional electron gas confined by a dielectric environment in the presence of both Rashba and Dresselhaus spin-orbit interactions. It is demonstrated that off-diagonal components of the conductivity tensor resulting from a delicate interplay between Rashba and Dresselhaus couplings lead to the hybridization of transverse electric and transverse magnetic surface electromagnetic modes localized at the interface. We show that the characteristics of these hybrid surface waves can be controlled by additional intense external off-resonant coherent pumping.

cond-mat.mes-hall↗

arXiv2016

Two-dimensional electron gas in the regime of strong light-matter coupling: Dynamical conductivity and all-optical measurements of Rashba and Dresselhaus coupling

A nonperturbative interaction of an electronic system with a laser field can substantially modify its physical properties. In particular, in two-dimensional (2D) materials with a lack of inversion symmetry, the achievement of a regime of strong light-matter coupling allows direct optical tuning of the strength of the Rashba spin-orbit interaction (SOI). Capitalizing on these results, we build a theory of the dynamical conductivity of a 2D electron gas with both Rashba and Dresselhaus SOIs coupled to an off-resonant high-frequency electromagnetic wave. We argue that strong light-matter coupling modifies qualitatively the dispersion of the electrons and can be used as a powerful tool to probe and manipulate the coupling strengths and adjust the frequency range where optical conductivity is essentially nonzero.

cond-mat.mes-hall↗

arXiv2016

Half-Skyrmion Spin Textures In Polariton Microcavities

We study the polarization dynamics of a spatially expanding polariton condensate under nonresonant linearly polarized optical excitation. The spatially and temporally resolved polariton emission reveals the formation of non-trivial spin textures in the form of a quadruplet polarization pattern both in the linear and circular Stokes parameters, and an octuplet in the diagonal Stokes parameter. The continuous rotation of the polariton pseudospin vector through the condensate due to TE-TM splitting exhibits an ordered pattern of half-skyrmions associated with a half-integer topological number. A theoretical model based on a driven-dissipative Gross-Pitaevskii equation coupled with an exciton reservoir describes the dynamics of the nontrivial spin textures through the optical spin-Hall effect.

physics.optics↗

arXiv2016

Polariton Spin Whirls

We report on the observation of spin whirls in a radially expanding polariton condensate formed under non-resonant optical excitation. Real space imaging of polarization- and time-resolved photoluminescence reveal a spiralling polarization pattern in the plane of the microcavity. Simulations of the spatiotemporal dynamics of a spinor condensate reveal the crucial role of polariton interactions with a spinor exciton reservoir. Harnessing spin dependent interactions between the exciton reservoir and polariton condensates allows for the manipulation of spin currents and the realization of dynamic collective spin effects in solid state systems.

cond-mat.mes-hall↗

arXiv2015

Switching waves in multi-level incoherently driven polariton condensates

We show theoretically that an open-dissipative polariton condensate confined within a trapping potential and driven by an incoherent pumping scheme gives rise to bistability between odd and even modes of the potential. Switching from one state to the other can be controlled via incoherent pulsing which becomes an important step towards construction of low-powered opto-electronic devices. The origin of the effect comes from modulational instability between odd and even states of the trapping potential governed by the nonlinear polariton-polariton interactions.

cond-mat.quant-gas↗

arXiv2014

Topological Effects on the Magnetoconductivity in Topological Insulators

Three-dimensional strong topological insulators (TIs) guarantee the existence of a 2-D conducting surface state which completely covers the surface of the TI. The TI surface state necessarily wraps around the TI's top, bottom, and two sidewalls, and is therefore topologically distinct from ordinary 2-D electron gases (2DEGs) which are planar. This has several consequences for the magnetoconductivity $Δσ$, a frequently studied measure of weak antilocalization which is sensitive to the quantum coherence time $τ_ϕ$ and to temperature. We show that conduction on the TI sidewalls systematically reduces $Δσ$, multiplying it by a factor which is always less than one and decreases in thicker samples. In addition, we present both an analytical formula and numerical results for the tilted-field magnetoconductivity which has been measured in several experiments. Lastly, we predict that as the temperature is reduced $Δσ$ will enter a wrapped regime where it is sensitive to diffusion processes which make one or more circuits around the TI. In this wrapped regime the magnetoconductivity's dependence on temperature, typically $1/T^2$ in 2DEGs, disappears. We present numerical and analytical predictions for the wrapped regime at both small and large field strengths. The wrapped regime and topological signatures discussed here should be visible in the same samples and at the same temperatures where the Altshuler-Aronov-Spivak (AAS) effect has already been observed, when the measurements are repeated with the magnetic field pointed perpendicularly to the TI's top face.

cond-mat.mes-hall↗

arXiv2013

Intersubband polaritonics revisited

We revisited the intersubband polaritonics - the branch of mesoscopic physics having a huge potential for optoelectronic applications in the infrared and terahertz domains - and found that, contrary to the general opinion, the Coulomb interactions play crucial role in the processes of light-matter coupling in the considered systems. Electron-electron and electron-hole interactions radically change the nature of the elementary excitations in these systems. We show that intersubband polaritons represent the result of the coupling of a photonic mode with collective excitations, and not non-interacting electron-hole pairs as it was supposed in the previous works on the subject.

cond-mat.mtrl-sci↗