A. V. Kavokin

Tamm plasmon polaritons: Slow and spatially compact light

We report on the first experimental observation of Tamm plasmon polaritons (TPPs) formed at the interface between a metal and a dielectric Bragg reflector (DBR). In contrast to conventional surface plasmons, TPPs have an in-plane wavevector less than the wavevector of light in vacuum, which allows for their direct optical excitation. The angular resolved reflectivity and transmission spectra of a GaAs∕AlAs DBR covered by Au films of various thicknesses show the resonances associated with the TPP at low temperatures and room temperature. The in-plane dispersion of TTPs is parabolic with an effective mass of 4×10−5 of the free electron mass.

Hybrid states of Tamm plasmons and exciton polaritons

Channeling of exciton polaritons in the plane of semiconductor microcavities can be achieved by the deposition of metallic mesas on the top of the semiconductor structure. We show theoretically that the regime of strong coupling between cavity polaritons and Tamm surface plasmons is possible in such structures. The effect is favorable for the spatial confinement of polaritons and the formation of hybrid one-dimensional plasmon-polariton modes.

Polariton-polariton scattering in microcavities: A microscopic theory

We apply the fermion commutation technique for composite bosons to polariton-polariton scattering in semiconductor planar microcavities. Derivations are presented in a simple and physically transparent fashion. A procedure of orthogonolization of the initial and final two-exciton state wave functions is used to calculate the effective scattering-matrix elements and the scattering rates. We show how the bosonic stimulation of the scattering appears in this full fermionic approach whose equivalence to the bosonization method is thus demonstrated in the regime of low exciton density. We find an additional contribution to polariton-polariton scattering due to the exciton oscillator strength saturation, which we analyze as well. We present a theory of the polariton-polariton scattering with opposite spin orientations and show that this scattering process takes place mainly via dark excitonic states. Analytical estimations of the effective scattering amplitudes are given.

Signature of the microcavity exciton―polariton relaxation mechanism in the polarization of emitted light

We have performed real and momentum space spin-dependent spectroscopies of spontaneously formed exciton polariton condensates for a nonresonant pumping scheme. Under a linearly polarized pump, our results can be understood in terms of spin-dependent Boltzmann equations in a two-state model. This suggests that relaxation into the ground state occurs after multiple phonon-scattering events and only one polariton-polariton scattering. For the circular pumping case, in which only excitons of one spin are injected, a bottleneck effect is observed, implying inefficient relaxation.

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 steplike 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.

Anisotropic optical spin Hall effect in semiconductor microcavities

Propagating, directionally dependent, polarized spin currents are created in an anisotropic planar semiconductor microcavity, via Rayleigh scattering of optically injected polaritons in the optical spin Hall regime. The influence of anisotropy results in suppression or enhancement of the pseudospin precession of polaritons scattered in specific directions. This is exploited to create intense spin currents by excitation on top of localized defects. A theoretical model considering the influence of the total effective magnetic field on the polariton pseudospin quantitatively reproduces the experimental observations.

Spin superfluidity of exciton polaritons in microcavities

Conventional spintronics uses the charged quasiparticles (electrons or hole) as spin carriers. Dephasing of spin currents in electronic systems is very fast, and propagation of a spin current in metal over more than 1 micron is extremely hard to achieve. On the other hand, electrically neutral spin carriers, exciton-polaritons, are known to propagate ballistically over tens and hundreds of microns. This is why the optically mediated spintronics is extremely promising for spin processing. Exciton polaritons in microcavities obey the bosonic statistics and exhibit superfluid properties. The spin current carried by a polariton superfluid would show no dissipation and no spin relaxation. Various coherent effects are expected, including the spin Meissner, spin Josephson and spin Aaronov-Bohm effects.