Spin transport in an Aharonov-Bohm ring with exchange interaction

We investigate spin-dependent conductance through a quantum Aharonov-Bohm ring containing localized electrons which interact with the propagating flow of electrons via exchange interaction of the ferromagnetic or antiferromagnetic type. We analyze the conductance oscillations as a function of both the chemical potential determined by the concentration of the carriers and external magnetic field. It is demonstrated that the amplitude of the conductance oscillations in the ballistic regime is governed by the value of the non-compensated spin localized in the ring. The results are in agreement with the concept of fractional quantization of the ballistic conductance, proposed by us earlie

One-dimensional Van Hove polaritons

Copyright © 2013 American Physical SocietyWe study the light-matter coupling of microcavity photons and an interband transition in a one-dimensional (1D) nanowire. Due to the Van Hove singularity in the density of states, resulting in a resonant character of the absorption line, the achievement of strong coupling becomes possible even without the formation of a bound state of an electron and a hole. The calculated absorption in the system and corresponding energy spectrum reveal anticrossing behavior characteristic of the formation of polariton modes. In contrast to the case of conventional exciton polaritons, the formation of 1D Van Hove polaritons will not be restricted to low temperatures and can be realized in any system with a singularity in the density of states

Excitons and interband terahertz transitions in narrow-gap carbon nanotubes

Copyright © 2013 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.2013 International Conference on Electromagnetics in Advanced Applications (ICEAA), Torino, Italy, 9 - 13 September 2013Post-print versionWe show, via a solution of the quasi-one-dimensional two-body problem applied to a Dirac system, that excitonic effects suppress the one-dimensional Van Hove singularity in single-walled carbon nanotubes with narrow band gaps.EPSRC (CAD) [Engineering and Physical Sciences Research Council]EU FP7 ITN SpinoptronicsFP7 IRSES project SPIN-METFP7 IRSES project QOCaNFP7 IRSES project CANTOREngineering and Physical Sciences Research Council: EPSRC (CAD)EU FP7 ITN SpinoptronicsFP7 IRSES project SPIN-METFP7 IRSES project QOCaNFP7 IRSES project CANTO

Bistability in microcavities with incoherent optical or electrical excitation

We consider a quantum well embedded in a zero-dimensional microcavity with a subwavelength grated mirror, where the x-linearly polarized exciton mode is strongly coupled to the cavity photon, while y-polarized excitons remain in the weak-coupling regime

Optical Anisotropy and Pinning of the Linear Polarization of Light in Semiconductor Microcavities

We report a 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 on 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 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.Comment: 15 pages, 2 figures, accepted in Solid State Communication

Boundary condition at the junction

The quantum graph plays the role of a solvable model for a two-dimensional network. Here fitting parameters of the quantum graph for modelling the junction is discussed, using previous results of the second author.Comment: Replaces unpublished draft on related researc

Spatial Coherence Properties of One Dimensional Exciton-Polariton Condensates

In this work, we combine a systematic experimental investigation of the power- and temperature-dependent evolution of the spatial coherence function, g(1)(r), in a one dimensional exciton-polariton channel with a modern microscopic numerical theory based on a stochastic master equation approach. The spatial coherence function g(1)(r) is extracted via high-precision Michelson interferometry, which allows us to demonstrate that in the regime of nonresonant excitation, the dependence g(1)(r) reaches a saturation value with a plateau, which is determined by the intensity of the pump and effective temperature of the crystal lattice. The theory, which was extended to allow for treating incoherent excitation in a stochastic frame, matches the experimental data with good qualitative and quantitative agreement. This allows us to verify the prediction that the decay of the off-diagonal long-range order can be almost fully suppressed in one dimensional condensate systems

Strong coupling of excitons in 2D MoSe2/hBN heterostructure with optical bound states in the continuum

We experimentally demonstrate strong exciton-photon coupling in a MoSe2/hBN heterostructure interfaced with an all-dielectric metasurface supporting high-Q bound states in the continuum. The resulting exciton-polaritons are probed by means of temperature- and angle-resolved reflectivity and photoluminescence. Our findings pave the way towards new-generation nonlinear planar polaritonic devices

Exciton-polaritons in a two-dimensional Lieb lattice with spin-orbit coupling

We study exciton-polaritons in a two-dimensional Lieb lattice of micropillars. The energy spectrum of the system features two flat bands formed from $S$ and $P_{x,y}$ photonic orbitals, into which we trigger bosonic condensation under high power excitation. The symmetry of the orbital wave functions combined with photonic spin-orbit coupling gives rise to emission patterns with pseudospin texture in the flat band condensates. Our work shows the potential of polariton lattices for emulating flat band Hamiltonians with spin-orbit coupling, orbital degrees of freedom and interactions