I. A. Shelykh

Polarization multistability of cavity polaritons.

New effects of polarization multistability and polarization hysteresis in a coherently driven polariton system in a semiconductor microcavity are predicted and theoretically analyzed. The multistability arises due to polarization-dependent polariton-polariton interactions and can be revealed in polarization resolved photoluminescence experiments. The pumping power required to observe this effect is 4 orders of magnitude lower than the characteristic pumping power in conventional bistable optical systems.

Optical Tamm states for the fabrication of polariton lasers

We propose to embed the ultrathin layer of an organic or inorganic material at the boundary between two specially designed periodic dielectric structures in order to achieve the strong coupling between Frenkel or Wannier-Mott excitons and optical Tamm states localized at the interface. This would allow the fabrication of polariton lasers without microcavities that could be easier from the technological point of view. Analytical formulas are given for the energies of optical Tamm states and the constant of their coupling to excitons.

Quantum splitter controlled by Rasha spin-orbit coupling

We propose the mesoscopic device based on the Rashba spin orbit interaction (SOI) that contains a gated ballistic Aharonov-Bohm (AB) ring with incoming lead and two asymmetrically situated outgoing leads. The variations of the Rashba coupling parameter induced by the gate voltage applied to the AB ring is shown to cause the redistribution of the carrier flux between the outgoing leads and spin polarization of the outgoing currents, thus allowing the system to manifest the properties of the quantum splitter and spin filter.

Interference of coherent polariton beams in microcavities: polarization-controlled optical gates

We demonstrate theoretically that the interaction of two degenerate condensates of exciton-polaritons in microcavities leads to polarization dependent parametric oscillations. The resonant polariton-polariton scattering is governed by the polarization of the condensates and can be fully suppressed for certain polarizations. A polarization controlled solid state optical gate is proposed.

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.

Quantized conductance in silicon quantum wires

The results of studying the quantum-mechanical staircase for the electron and hole conductance of one-dimensional channels obtained by the split-gate method inside self-assembled silicon quantum wells are reported. The characteristics of quantum wells formed spontaneously between the heavily doped δ-shaped barriers at the Si(100) surface as a result of nonequilibrium boron diffusion are analyzed first. To this end, secondary-ion mass spectrometry, and also the detection of angular dependences of the cyclotron resonance and ESR, is used; these methods make it possible to identify both the crystallographic orientation of the self-assembled quantum wells and the ferroelectric properties of heavily doped δ-shaped barriers. Since the obtained silicon quantum wells are ultrathin (∼2 nm) and the confining δ-shaped barriers feature ferroelectric properties, the quantized conductance of one-dimensional channels is first observed at relatively high temperatures (T≥77 K). Further, the current-voltage characteristic of the quantum-mechanical conductance staircase is studied in relation to the kinetic energy of electrons and holes, their concentration in the quantum wells, and the crystallographic orientation and modulation depth of electrostatically induced quantum wires. The results show that the magnitude of quantum steps in electron conductance of crystallographically oriented n-type wires is governed by anisotropy of the Si conduction band and is completely consistent with the valence-valley factor for the [001] (G0=4e2/h and gv=2) and [011] (G0=8e2/h and gv=4) axes in the Si(100) plane. In turn, the quantum staircase of the hole conductance of p-Si quantum wires is caused by independent contributions of the one-dimensional (1D) subbands of the heavy and light holes; these contributions manifest themselves in the study of square-section quantum wires in the doubling of the quantum-step height (G0=4e2/h), except for the first step (G0=2e2/h) due to the absence of degeneracy of the lower 1D subband. An analysis of the heights of the first and second quantum steps indicates that there is a spontaneous spin polarization of the heavy and light holes, which emphasizes the very important role of exchange interaction in the processes of 1D transport of individual charge carriers. In addition, the temperature-and field-related inhibition of the quantum conductance staircase is demonstrated in the situation when kT and the energy of the field-induced heating of the carriers become comparable to the energy gap between the 1D subbands. The use of the split-gate method made it possible to detect the effect of a drastic increase in the height of the quantum conductance steps when the kinetic energy of electrons is increased; this effect is most profound for quantum wires of finite length, which are not described under conditions of a quantum point contact. It is shown in the concluding section of this paper that detection of the quantum-mechanical conductance under the conditions of sweeping the kinetic energy of the charge carriers can act as an experimental test aiding in separating the effects of quantum interference in modulated quantum wires against the background of Coulomb oscillations as a result of the formation of QDs between the delta-shaped barriers.

Effects of Bose-Einstein condensation of exciton polaritons in microcavities on the polarization of emitted light

It is shown theoretically that Bose condensation of spin-degenerated exciton-polaritons results in spontaneous buildup of the linear polarization in emission spectra of semiconductor microcavities. The linear polarization degree is a good order parameter for the polariton Bose condensation. If spin-degeneracy is lifted, an elliptically polarized light is emitted by the polariton condensate. The main axis of the ellipse rotates in time due to self-induced Larmor precession of the polariton condensate pseudospin. The polarization decay time is governed by the dephasing induced by the polariton-polariton interaction and strongly depends on the statistics of the condensed state.

Superradiant terahertz emission by dipolaritons.

Dipolaritons are mixed light-matter quasiparticles formed in double quantum wells embedded in microcavities. Because of resonant coupling between direct and indirect excitons via electronic tunneling, dipolaritons possess large dipole moments. Resonant excitation of the cavity mode by a short pulse of light induces oscillations of the indirect exciton density with a characteristic frequency of Rabi flopping. This results in oscillations of a classical Hertz dipole array which generate supperradiant emission on a terahertz (THz) frequency. The resulting THz signal may be enhanced using the supplementary THz cavity in the weak coupling regime.

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.

Optical anisotropy and pinning of the linear polarization of light in semiconductor microcavities

We report strong experimental evidence of the optical anisotropy in a CdTe-based microcavity: the polarization of light is pinned to one of the crystallographic axes independently of the polarization of the excitation. The polarization degree depends strongly on the excitation power, reaching almost 100% in the stimulated regime. The relaxation time of the polarization is about 1 ns. We argue that all of this is an effect of a splitting of the polariton doublet at k = 0. We consider different sources for the splitting and conclude that the most likely one is optical birefringence in the mirrors and/or the cavity.