arXiv subjects

A. V. Nalitov

Publications and source records attributed to A. V. Nalitov.

24 records · Page 2Linked to original sources

arXiv2014

Voltage control of the spin-dependent interaction constants of Dipolaritons and its application to Optical Parametric Oscillator

Dipolariton is a voltage controlled mixture of direct and indirect excitons in asymmetric double quantum wells coupled by resonant carrier tunneling, and a microcavity photon. We calculate the voltage dependence of the spin-singlet and spin-triplet interaction parameters $α_{1}$ and $α_{2}$. Both parameters can reach values one order of magnitude larger than that of exciton-polaritons thanks to the strong interaction between indirect excitons. We show that the variation of the indirect exciton fraction of the dipolaritons induces a changes of sign of $α_{2}$ increasing voltage: the interaction passes from attractive to repulsive. For large enough voltage $α_{2}$ becomes larger than $α_{1}$ which in principle can lead to the formation of a circularly polarised dipolariton condensate. We propose an application of the $α_{2}$ dependence to a voltage-controlled dipolaritonic optical parametric oscillator. The change of sign of $α_{2}$ allows an on-site control of the linear polarization degree of the optical signal and its on-demand inversion.

cond-mat.mes-hall↗

arXiv2014

Polariton $\mathbb{Z}$ Topological Insulator

Recent search for optical analogues of topological phenomena mainly focuses on mimicking the key feature of quantum Hall and quantum spin Hall effects (QHE and QSHE): edge currents protected from disorder. QHE relies on time-reversal symmetry breaking, which can be realised in photonic gyromagnetic crystals. In the optical range, the weak magneto-optical activity may be replaced with helical design of coupled waveguides, converting light propagation into a time-dependent perturbation. Finally, optical QHE due to artificial gauge fields was predicted in microcavity lattices. Here, we consider honeycomb arrays of microcavity pillars as an alternative optical-frequency 2D topological insulator. We show that the interplay between the photonic spin-orbit coupling natively present in this system and the Zeeman splitting of exciton-polaritons in external magnetic fields leads to the opening of a non-trivial gap characterised by $C=\pm 2$ set of band Chern numbers and to the formation of topologically protected one-way edge states.

cond-mat.mes-hall↗

arXiv2014

Spin-orbit coupling and optical spin Hall effect in photonic graphene

We study the spin-orbit coupling induced by the splitting between TE and TM optical modes in a photonic honeycomb lattice. Using a tight-binding approach, we calculate analytically the band structure. Close to the Dirac point,we derive an effective Hamiltonian. We find that the local reduced symmetry ($\mathrm{D_{3h}}$) transforms the TE-TM effective magnetic field into an emergent field with a Dresselhaus symmetry. As a result, particles become massive, but no gap opens. The emergent field symmetry is revealed by the optical spin Hall effect.

cond-mat.mes-hall↗

arXiv2013

Nonlinear Optical Probe of Indirect Excitons

We propose the application of nonlinear optics for studies of spatially indirect excitons in coupled quantum wells. We demonstrate, that despite their vanishing oscillator strength, indirect excitons can strongly contribute to the photoinduced reflectivity and Kerr rotation. This phenomenon is governed by the interaction between direct and indirect excitons. Both dark and bright states of indirect excitons can be probed by these nonlinear optical techniques.

cond-mat.mes-hall↗

arXiv2012

Skyrmion Formation and Optical Spin-Hall Effect in an Expanding Coherent Cloud of Indirect Excitons

We provide a theoretical description of the polarization pattern and phase singularities experimentally evidenced recently in a condensate of indirect excitons [H. High et al., Nature 483, 584-588 (2012)]. We show that the averaging of the electron and hole orbital motion leads to a comparable spin-orbit interaction for both type of carriers. We demonstrate that the interplay between a radial coherent flux of bright indirect excitons and the Dresselhaus spin-orbit interaction results in the formation of spin domains and of topological defects similar to Skyrmions. We reproduce qualitatively all the features of the experimental data and obtain polarization pattern as in the optical spin Hall effect despite the different symmetry of the spin-orbit interactions.

cond-mat.mes-hall↗

arXiv2012

Ratchet effects in two-dimensional systems with a lateral periodic potential

Radiation-induced ratchet electric currents have been studied theoretically in graphene with a periodic noncentrosymmetric lateral potential. The ratchet current generated under normal incidence is shown to consist of two contributions, one of them being polarization-independent and proportional to the energy relaxation time, and another controlled solely by elastic scattering processes and sensitive to both the linear and circular polarization of radiation. Two realistic mechanisms of electron scattering in graphene are considered. For short-range defects, the ratchet current is helicity-dependent but independent of the direction of linear polarization. For the Coulomb impurity scattering, the ratchet current is forbidden for the radiation linearly polarized in the plane perpendicular to the lateral-potential modulation direction. For comparison, the ratchet currents in a quantum well with a lateral superlattice are calculated at low temperatures with allowance for the dependence of the momentum relaxation time on the electron energy.

cond-mat.mes-hall↗