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I. A. Shelykh

Publications and source records attributed to I. A. Shelykh.

At least 181 records · Page 10Linked to original sources

Fractional quantization of the ballistic conductance in electron and hole systems

In the present article we give a brief overview of the theories of the 0.7 anomaly of the ballistic conductance. The special attantion is given to the concept of a fractional quantization of the ballistic conductance arising from exchange interaction of the Heisenberg type between the carrier localized in the region of the quantum point contact and freely propagating carriers in electron and hole systems. ----- Brotaskömmtun skotleiðninnar í einvíðum rafeinda og holukerfum Í grein þessari verður skömmtun skotleiðninnar í einvíðum kerfum útskýrð og farið yfir nýjustu og helstu fræðilíkön á sviði \LDQ 0,7 fráviksins \RDQ og tengdra fyrirbrigða í einvíðum rafeinda og holukerfum. Við kynnum hugmynd okkar um að brotaskömmtun skotleiðninnar leiði af Heisenberg skiptaverkun milli staðbundins rafbera í skammtapunktsnertunni og frjálsra leiðnirafbera og sýnum fram á að hegðun leiðninnar er eigindlega ólík milli rafeinda og holukerfa.

cond-mat.mes-hall↗

Stimulated emission of terahertz radiation by semiconductor microcavities

We show that planar semiconductor microcavities in the strong coupling regime can be used as sources of stimulated terahertz (THz) radiation. Emitted THz photons would have a frequency of the spliting of the cavity polariton modes. The optical transition between upper and lower polariton branches is allowed due to mixing of the upper polariton state with one of excited exciton states. This transition is stimulated in the polariton laser regime.

cond-mat.mes-hall↗

Rotons in a hybrid Bose-Fermi system

We calculate the spectrum of elementary excitations in a two-dimensional exciton superfluid in the vicinity of a two-dimensional electron gas. We show that attraction of excitons due to their scattering with free electrons may lead to formation of a roton minimum. The energy of this minimum may go below the ground state energy which manifests breaking of the superfluidity. The Berezinsky-Kosterlitz-Thouless phase transition temperature decreases due to the exciton-exciton attraction mediated by electrons.

cond-mat.quant-gas↗

Optically and electrically controlled polariton spin transistor

We propose two schemes of a novel spin-optronic device, optical analog of Datta and Das spin transistor for the electrons. The role of ferromagnetic contacts is played by one-dimensional polariton channels with strong TE-TM splitting. A symmetric 2D trap plays a role of the non-magnetic active region. The rotation of the polarization of the pulse in this region can be achieved either due to its interaction with a spatially confined polariton condensate created resonantly by a circular polarized laser, either due to the splitting between the two linear polarizations of the excitons, controlled electrically by use of metallic gate.

cond-mat.mes-hall↗

Phonon-mediated Josephson oscillations in excitonic and polaritonic condensates

We analyze theoretically the role of the exciton-phonon interactions in phenomena related to the Josephson effect between two spatially separated exciton and exciton-polariton condensates. We consider the role of the dephasing introduced by phonons in such phenomena as Josephson tunneling, self-trapping and spontaneous polarization separation. In the regime of cw pumping we find a remarkable bistability effect arising from exciton- exciton interactions as well as regimes of self- sustained regular and chaotic oscillations.

cond-mat.quant-gas↗

Polaritonic analogue of Datta and Das spin transistor

We propose the scheme of a novel spin-optronic device, optical analog of Datta and Das spin transistor for the electrons. The role of the ferromagnetic-nonmagnetic contact is played by a spatially confined cavity polariton BEC. The condensate is responsible for the appearance of effective magnetic field which rotates the spin state of a propagating pulse of polaritons allowing to tune the transmittivity of the device.

cond-mat.mes-hall↗

Spin Transistor and Quantum Spin Hall Effects in CdBxF2-x - p-CdF2 - CdBxF2-x Sandwich Nanostructures

Planar CdBxF2-x - p-CdF2 - CdBxF2-x sandwich nanostructures prepared on the surface of the n-type CdF2 bulk crystal are studied to register the spin transistor and quantum spin Hall effects. The current-voltage characteristics of the ultra-shallow p+-n junctions verify the CdF2 gap, 7.8 eV, and the quantum subbands of the 2D holes in the p-type CdF2 quantum well confined by the CdBxF2-x delta-barriers. The temperature and magnetic field dependencies of the resistance, specific heat and magnetic susceptibility demonstrate the high temperature superconductor properties for the CdBxF2-x delta-barriers. The value of the superconductor energy gap, 102.06 meV, determined by the tunneling spectroscopy method appears to be in a good agreement with the relationship between the zero-resistance supercurrent in superconductor state and the conductance in normal state at the energies of the 2D hole subbands. The results obtained are evidence of the important role of the multiple Andreev reflections in the creation of the high spin polarization of the 2D holes in the edged channels of the sandwich device. The high spin hole polarization in the edged channels is shown to identify the mechanism of the spin transistor and quantum spin Hall effects induced by varying the top gate voltage, which is revealed by the first observation of the Hall quantum conductance staircase.

cond-mat.mes-hall↗

Quantum size effects in Pb layers with absorbed Kondo adatoms: Determination of the exchange coupling constant

We consider the magnetic interaction of manganese phtalocyanine (MnPc) absorbed on Pb layers which were grown on a Si substrate. We perform an ab-initio calculation of the density of states and Kondo temperature as function of the number of Pb monolayers. Comparison to experimental data [Phys. Rev. Lett. 99, 256601 (2007)] then allows us to determine the exchange coupling constant J between the spins of the adsorbed molecules and those of the Pb host. This approach gives rise to a general and reliable method for obtaining J, by combining experimental and numerical results.

cond-mat.str-el↗

Fano-Kondo Spin Filter

We study spin-dependent conductance in a system composed of a ferromagnetic (FM) Scanning Tunneling Microscope (STM) tip coupled to a metallic host surface with an adatom. The Kondo resonance is taken into account via the Doniach-Sunjic spectral function. For short lateral tip-adatom distances and due to the interplay between Kondo physics, quantum interfering effects and the ferromagnetism of the tip, a spin-splitting of the Fano-Kondo line shape arises in the conductance. A strong enhancement of the Fano-Kondo profile for the majority spin component of the FM tip is observed. When the tip is placed on the adatom, this gives a conductance 100 % polarized for a particular range of bias voltage. The system thus can be used as a powerful generator of spin polarized currents.

cond-mat.str-el↗

Proposal for a Mesoscopic Optical Berry-Phase Interferometer

We propose a novel spin-optronic device based on the interference of polaritonic waves traveling in opposite directions and gaining topological Berry phase. It is governed by the ratio of the TE-TM and Zeeman splittings, which can be used to control the output intensity. Because of the peculiar orientation of the TE-TM effective magnetic field for polaritons, there is no analogue of the Aharonov- Casher phase shift existing for electrons.

cond-mat.mes-hall↗

Spin-Polarized STM for a Kondo adatom

We investigate the bias dependence of the tunneling conductance between a spin-polarized (SP) scanning tunneling microscope (STM) tip and the surface conduction states of a normal metal with a Kondo adatom. Quantum interference between tip-host metal and tip-adatom-host metal conduction paths is studied in the full range of the Fano parameter $q$. The spin-polarized STM gives rise to a splitting of the Kondo peak and asymmetry in the zero-bias anomaly depending on the lateral tip-adatom distance. For increasing lateral distances, the Kondo peak-splitting shows a strong suppression and the spin-polarized conductance exhibits the standard Fano-Kondo profile.

cond-mat.str-el↗

Optical spectra of a quantum dot in a microcavity in the nonlinear regime

The optical emission spectrum of a quantum dot in strong coupling with the single mode of a microcavity is obtained in the nonlinear regime. We study how exciton-exciton interactions alter the emission spectrum of the system, bringing the linear Rabi doublet into a multiplet structure that is strongly dependent on the cavity-exciton energy detuning. We emphasise how nonlinearity can be used to evidence the genuine quantum nature of the coupling by producing satellites peaks of the Rabi doublet that originate from the quantized energy levels of the interactions.

cond-mat.mes-hall↗

Magnetic field effect on polarization and dispersion of exciton-polaritons in planar microcavities

The non-local dielectric response theory is extended to describe oblique reflection of light from quantum wells subjected to the magnetic field. This allows us to calculate the dispersion and polarization of the exciton-polariton modes in semiconductor microcavities in the presence of a magnetic field normal to the plane of the structure. We show that due to the interplay between the exciton Zeeman splitting and TE-TM splitting of the photon modes, four polariton dispersion branches are formed with a polarization gradually changing from circular in the exciton-like part to linear in the photon-like part of each branch. Faraday rotation in quantum microcavities is shown to be strongly enhanced as compared with the rotation in quantum wells.

cond-mat.mes-hall↗

Entangled photon pairs produced by a quantum dot strongly coupled to a microcavity

We show theoretically that entangled photon pairs can be produced on demand through the biexciton decay of a quantum dot strongly coupled to the modes of a photonic crystal. The strong coupling allows to tune the energy of the mixed exciton-photon (polariton) eigenmodes, and to overcome the natural splitting existing between the exciton states coupled with different linear polarizations of light. Polariton states are moreover well protected against dephasing due to their lifetime ten to hundred times shorter than that of a bare exciton. Our analysis shows that the scheme proposed can be achievable with the present technology.

quant-ph↗

Optical circuits based on Polariton Neurons in Semiconductor Microcavities

By exploiting the polarization multistability of polaritons, we show that polarized signals can be conducted in the plane of a semiconductor microcavity along controlled channels or "neurons". Furthermore due to the interaction of polaritons with opposite spins it is possible to realize binary logic gates operating on the polarization degree of freedom. Multiple gates can be integrated together to form an optical circuit contained in a single semiconductor microcavity.

cond-mat.mes-hall↗

Suppression of Zeeman splitting and polarization steps in localized exciton-polariton condensates

We show that the condensation of exciton-polaritons in semiconductor microcavities in an applied magnetic field manifests itself in the quenching of the Zeeman splitting of an elliptically polarized condensate. The circular polarization degree of a localized condensate with a finite number of particles increases as a function of the magnetic field with a step-like behavior. The width of each polarization step is fixed by the polariton-polariton interaction constants and the number of steps is fixed by the number of polaritons in the condensate. The magnetic susceptibility of the condensate depends qualitatively on the parity of the number of polaritons.

cond-mat.mes-hall↗

Fractional quantization of ballistic conductance in 1D hole systems

We analyze the fractional quantization of the ballistic conductance associated with the light and heavy holes bands in Si, Ge and GaAs systems. It is shown that the formation of the localized hole state in the region of the quantum point contact connecting two quasi-1D hole leads modifies drastically the conductance pattern. Exchange interaction between localized and propagating holes results in the fractional quantization of the ballistic conductance different from those in electronic systems. The value of the conductance at the additional plateaux depends on the offset between the bands of the light and heavy holes, Δ, and the sign of the exchange interaction constant. For Δ=0 and ferromagnetic exchange interaction, we observe additional plateaux around the values 7e^{2}/4h, 3e^{2}/h and 15e^{2}/4h, while antiferromagnetic interaction plateaux are formed around e^{2}/4h, e^{2}/h and 9e^{2}/4h. For large Δ, the single plateau is formed at e^2/h.

cond-mat.mes-hall↗