arXiv subjects

A. N. Poddubny

Publications and source records attributed to A. N. Poddubny.

At least 19 recordsLinked to original sources

arXiv2021

Transverse magnetic routing of light emission in hybrid plasmonic-semiconductor nanostructures: Towards operation at room temperature

We study experimentally and theoretically the temperature dependence of transverse magnetic routing of light emission from hybrid plasmonic-semiconductor quantum well structures where the exciton emission from the quantum well is routed into surface plasmon polaritons propagating along a nearby semiconductor-metal interface. In II-VI and III-V direct band semiconductors the magnitude of routing is governed by the circular polarization of exciton optical transitions, that is induced by a magnetic field. For structures comprising a (Cd,Mn)Te/(Cd,Mg)Te diluted magnetic semiconductor quantum well we observe a strong directionality of the emission up to 15% at low temperature of 20 K and magnetic field of 485 mT due to giant Zeeman splitting of holes mediated via the strong exchange interaction with Mn$^{2+}$ ions. For increasing temperatures towards room-temperature the magnetic susceptibility decreases and the directionality strongly decreases to 4% at T = 45 K. We also propose an alternative design based on a non-magnetic (In,Ga)As/(In,Al)As quantum well structure, suitable for higher temperatures. According to our calculations, such structure can demonstrate emission directionality up to 5% for temperatures below 200 K and moderate magnetic fields of 1 T.

cond-mat.mtrl-sci↗

arXiv2020

Plasmon to exciton spin conversion in semiconductor-metal hybrid structures

Optical control of electronic spins is the basis for ultrafast spintronics: circularly polarized light in combination with spin-orbit coupling of the electronic states allows for spin manipulation in condensed matter. However, the conventional approach is limited to spin orientation along one particular orientation that is dictated by the direction of photon propagation. Plasmonics opens new capabilities, allowing one to tailor the light polarization at the nanoscale. Here, we demonstrate ultrafast optical excitation of electron spin on femtosecond time scales via plasmon to exciton spin conversion. By time-resolving the THz spin dynamics in a hybrid (Cd,Mn)Te quantum well structure covered with a metallic grating, we unambiguously determine the orientation of the photoexcited electron spins which is locked to the propagation direction of surface plasmon-polaritons. Using the spin of the incident photons as additional degree of freedom, one can orient the photoexcited electron spin at will in a two-dimensional plane.

cond-mat.mtrl-sci↗

arXiv2020

Polarized edge state emission from topological spin phases of trapped Rydberg excitons in Cu$_2$O

In one dimensional chains of trapped Rydberg excitons in cuprous oxide semiconductor the topological spin phase has been recently predicted [Phys. Rev. Lett. 123, 126801 (2019); arXiv:1903.11951]. This phase is characterized by the diluted antiferromagnetic order of $p$-shell exciton angular momenta-$1$ and the edge states behaving akin spin-$1/2$ fermions. Here we study the properties of the ground state in the finite chains and its fine structure resulting from the effective interaction of the edge spins. We demonstrate that these edge states can detected optically via the enhancement of the circular polarization of the edge emission as compared with the emission from the bulk. We calculate the distribution of the exciton angular momentum vs. trap number in the chain numerically and analytically based on the variational ansatz.

cond-mat.mes-hall↗

arXiv2020

Doppler-Raman crossover in resonant scattering

We consider theoretically light scattering by a resonant layer that periodically moves in real space. At small frequencies of motion the scattered light spectrum reveals the frequency shift that is governed by the Doppler effect. At higher motion frequencies, the scattered light spectra acquire sidebands stemming from the Raman effect. We investigate the crossover between these two regimes and propose a realistic quantum well structure for its observation.

physics.optics↗

arXiv2020

Magneto-toroidal nonreciprocity of second harmonic generation

The Lorentz reciprocity principle is a fundamental concept that governs light propagation in any optically linear medium in zero magnetic field. Here, we demonstrate experimentally a novel mechanism of reciprocity breaking in nonlinear optics driven by the toroidal moment. Using high-resolution femtosecond spectroscopy at optical electronic resonances in the magnetoelectric antiferromagnet CuB$_2$O$_4$, we show that by controlling the nonlinear interference of coherent sources of second harmonic generation originating from the toroidal spin order, applied magnetic field, and noncentrosymmetric crystal structure, we induce a huge nonreciprocity approaching 100% for opposite magnetic fields. The experimental results are corroborated by a convincing theoretical analysis based on the magnetic and crystal symmetry. These findings open new degrees of freedom in the nonlinear physics of electronic and magnetic structures and pave the way for future nonreciprocal spin-optronic devices operating on the femtosecond time scale.

cond-mat.mtrl-sci↗

arXiv2019

Optomechanical tension and crumpling of resonant membranes

We predict that illumination by a plane electromagnetic wave of optically resonant membranes, such as graphene or monolayers of transition metal dichalcogenides, directly affects their mechanical tension. The induced optomechanical tension is anisotropic and, depending on the spectral detuning from the resonance, can be both positive and negative. In the latter case, it can overcome the bending rigidity of the membrane leading to transition to the crumpled phase. The instability caused by optomechanical heating of flexural vibrations is also considered.

cond-mat.mes-hall↗

arXiv2019

Topological spin phases of trapped Rydberg excitons in Cu$_2$O

We study theoretically Rydberg excitons in one-dimensional chains of traps in Cu$_2$O coupled via the van der Waals interaction. The triplet of optically active $p$-shell states acts as an effective spin-$1$ and the interactions between the excitons are strongly spin-dependent. We predict that the system {has the} topological Haldane phase with the diluted antiferromagnetic order, long-range string correlations, and finite excitation gap. We also analyze the effect of the trap geometry and interactions anisotropy on the Rydberg exciton spin states and demonstrate that a rich spin phase diagram can be realized showing high tunability of the Rydberg exciton platform.

cond-mat.mes-hall↗

arXiv2018

Transverse Magneto-Optical Kerr Effect at Narrow Optical Resonances

Magneto-optical spectroscopy based on the transverse magneto-optical Kerr effect (TMOKE) is a sensitive method for investigation of magnetically-ordered media. However, in magnetic materials the optical transitions are usually characterized by spectrally broad resonances with widths considerably exceeding the Zeeman splitting in the magnetic field. Here we investigate experimentally and theoretically the TMOKE in the vicinity of relatively narrow optical resonances provided by confined quantum systems. For experimental demonstration we use the exciton resonance in a (Cd,Mn)Te diluted magnetic semiconductor quantum well, where the strong exchange interaction with magnetic ions enables the giant Zeeman splitting of exciton spin states $Δ$ in magnetic fields of a few Tesla. In the weak coupling regime, when the splitting $Δ$ is smaller than the spectral broadening of the optical transitions $Γ$, the TMOKE magnitude grows linearly with the increase of the Zeeman splitting and its spectrum has an S-shape, which remains virtually unchanged in this range. In the strong coupling regime ($Δ>Γ$) the TMOKE magnitude saturates, while its spectrum is strongly modified resulting in the appearance of two separate peaks. The TMOKE is sensitive not only to the sample surface but can be used to probe the confined electronic states in depth if the upper layer is sufficiently transparent. Our results demonstrate that TMOKE of spectrally narrow resonances serves as a versatile tool for probing the charge and spin structure of electronic states in various confined quantum systems and can be used for spin tomography in combination with the conventional polar Kerr effect.

cond-mat.mtrl-sci↗

arXiv2018

Optomechanical Kerker effect

Tunable directional scattering is of paramount importance for operation of antennas, routing of light, and design of topologically protected optical states. For visible light scattered on a nanoparticle the directionality could be provided by the Kerker effect, exploiting the interference of electric and magnetic dipole emission patterns. However, magnetic optical resonances in small sub-100-nm particles are relativistically weak. Here, we predict inelastic scattering with the unexpectedly strong tunable directivity up to 5.25 driven by a trembling of small particle without any magnetic resonance. The proposed optomechanical Kerker effect originates from the vibration-induced multipole conversion. We also put forward an optomechanical spin Hall effect, the inelastic polarization-dependent directional scattering. Our results uncover an intrinsically multipolar nature of the interaction between light and mechanical motion. They apply to a variety of systems from cold atoms to two-dimensional materials to superconducting qubits and can be instructive to engineer chiral optomechanical coupling.

physics.optics↗

arXiv2018

Observation and control of nonlinear electromagnetic topological edge states

Topological photonics has recently emerged as a route to realize robust optical circuitry, and nonlinear effects are expected to enable tunability of topological states with the light intensity. Here we realize experimentally nonlinear self-induced spectral tuning of the electromagnetic topological edge states in an array of coupled nonlinear resonators in a pump-probe experiment. In a weakly nonlinear regime, we observe that resonators frequencies exhibit spectral shifts, that are concentrated mainly at the edge mode affecting only weakly the bulk modes. For a strong pumping, we describe several scenarios of the transformation of the edge states and their hybridization with bulk modes, and also predict a parametrically driven transition from topological to unstable regimes.

physics.optics↗

arXiv2017

Routing the emission of a near-surface light source by a magnetic field

Magneto-optical phenomena such as the Faraday and Kerr effects play a decisive role for establishing control over polarization and intensity of optical fields propagating through a medium. Intensity effects where the direction of light emission depends on the orientation of the external magnetic field are of particular interest as they can be used for routing the light. We report on a new class of transverse emission phenomena for light sources located in the vicinity of a surface, where directionality is established perpendicularly to the externally applied magnetic field. We demonstrate the routing of emission for excitons in a diluted-magnetic-semiconductor quantum well. The directionality is significantly enhanced in hybrid plasmonic semiconductor structures due to the generation of plasmonic spin fluxes at the metal-semiconductor interface.

cond-mat.mtrl-sci↗

arXiv2017

Valley and spin splittings in PbSe nanowires

We use an empirical tight-binding approach to calculate electron and hole states in [111]-grown PbSe nanowires. We show that the valley-orbit and spin-orbit splittings are very sensitive to the atomic arrangement within the nanowire elementary cell and differ for [111]-nanowires with microscopic $D_{3d}$, $C_{2h}$ and $D_{3}$ symmetries. For the nanowire diameter below 4 nm the valley-orbit splittings become comparable with the confinement energies and the $\boldsymbol{k}\cdot\boldsymbol{p}$ method is inapplicable. Nanowires with the $D_{3}$ point symmetry having no inversion center exhibit giant spin splitting $E = αk_z$, linear in one-dimensional wave vector $k_z$, with the constant $α$ up to 1 eV$\cdot$Å.

cond-mat.mes-hall↗

arXiv2016

Phonoritonic crystals with synthetic magnetic field for acoustic diode

We develop a rigorous theoretical framework to describe light-sound interaction in the laser-pumped periodic multiple-quantum-well structure accounting for the hybrid phonon-polariton excitations, termed as phonoritons. We show that phonoritons exhibit the pumping-induced synthetic magnetic field in the artificial "coordinate-energy" space, that makes transmission of left- and right- going waves different. The transmission nonreciprocity allows to use such phonoritonic crystals with realistic parameters as optically controlled nanoscale acoustic diodes.

cond-mat.mes-hall↗

arXiv2016

Multiple quantum wells for PT-symmetric phononic crystals

We demonstrate that the parity-time symmetry for sound is realized in the laser-pumped multiple-quantum-well structure. Breaking of the parity-time symmetry for the phonons with wave vectors corresponding to the Bragg condition makes the structure a highly-selective acoustic wave amplifier. Single-mode distributed feedback phonon lasing is predicted for structures with realistic parameters.

cond-mat.mes-hall↗

arXiv2016

Tuning optical properties of Ge nanocrystals by Si shell

We present a theoretical study of Ge-core/Si-shell nanocrystals in a wide bandgap matrix and compare the results with experimental data obtained from the samples prepared by co-sputtering. The empirical tight-binding technique allows us to account for the electronic structure under strain on the atomistic level. We find that a Si shell as thick as 1 monolayer is enough to reduce the radiative recombination rate as a result of valley $L - X$ cross-over. Thin Si shell leads to a dramatic reduction of the optical bandgap from visible to near-infrared range, which is promising for photovoltaics and photodetector applications. Our detailed analysis of the structure of the confined electron and hole states in real and reciprocal spaces indicates that the type-II heterostructure is not yet achieved for Si shells with the thickness below 0.8 nm, despite some earlier theoretical predictions. The energy levels of holes are affected by the Si shell stronger than the electron states, even though holes are completely confined to the Ge core. This occurs probably due to a strong influence of strain on the band offsets.

cond-mat.mes-hall↗

arXiv2016

Enhanced photonic spin Hall effect with subwavelength topological edge states

Photonic structures offer unique opportunities for controlling light-matter interaction, including the photonic spin Hall effect associated with the transverse spin-dependent displacement of light that propagates in specially designed optical media. However, due to small spin-orbit coupling, the photonic spin Hall effect is usually weak at the nanoscale. Here we suggest theoretically and demonstrate experimentally, in both optics and microwave experiments, the photonic spin Hall effect enhanced by topologically protected edge states in subwavelength arrays of resonant dielectric particles. Based on direct near-field measurements, we observe the selective excitation of the topological edge states controlled by the handedness of the incident light. Additionally, we reveal the main requirements to the symmetry of photonic structures to achieve a topology-enhanced spin Hall effect, and also analyse the robustness of the photonic edge states against the long-ranged coupling.

cond-mat.mes-hall↗

arXiv2015

Enhancement of magnetic resonance imaging with metasurfaces

Magnetic resonance imaging (MRI) is the cornerstone technique for diagnostic medicine, biology, and neuroscience. This imaging method is highly innovative, noninvasive and its impact continues to grow. It can be used for measuring changes in the brain after enhanced neural activity, detecting early cancerous cells in tissue, as well as for imaging nanoscale biological structures, and controlling fluid dynamics, and it can be beneficial for cardiovascular imaging. The MRI performance is characterized by a signal-to-noise ratio, however the spatial resolution and image contrast depend strongly on the scanner design. Here, we reveal how to exploit effectively the unique properties of metasurfaces for the substantial improvement of MRI efficiency. We employ a metasurface created by an array of wires placed inside the MRI scanner under an object, and demonstrate a giant enhancement of the magnetic field by means of subwavelength near-field manipulation with the metasurface, thus strongly increasing the scanner sensitivity, signal-to-noise ratio, and image resolution. We demonstrate experimentally this effect for a commercially available MRI scanner and a biological tissue sample. Our results are corroborated by measured and simulated characteristics of the metasurface resonator, and our approach can enhance dramatically functionalities of widely available low-field MRI devices.

physics.med-ph↗

arXiv2015

Phase spectroscopy of topological invariants in photonic crystals

We propose a method of measuring topological invariants of a photonic crystal through phase spectroscopy. We show how the Chern numbers can be deduced from the winding numbers of the reflection coefficient phase. An explicit proof of existence of edge states in system with nonzero reflection phase winding number is given. The method is illustrated for one- and two-dimensional photonic crystals of nontrivial topology.

cond-mat.mes-hall↗