Symmetry breaking and superfluid currents in a split-ring spinor polariton condensate

Bosonic condensates of spin-less non-interacting particles confined on a ring cannot propagate circular periodic currents once rotation symmetry of the system is broken. However a persistent current may appear due to inter-particle interactions exceeding some critical strength. In this up-critical regime breaking of the symmetry between the clockwise and anticlockwise rotations takes place. We consider this symmetry-breaking scenario in the case of a spinor condensate of exciton polaritons trapped on a ring split by a potential barrier. Due to the intrinsic symmetry of the effective spin-orbit interaction which stems from the linear splitting between transverse-electric and transverse-magnetic microcavity modes, the potential barrier blocks the circulating current and imposes linear polarization patterns. On the other hand, circularly polarized polaritons form circular currents propagating in opposite directions with equal absolute values of angular momentum. In the presence of inter-particle interactions, the symmetry of clockwise and anticlockwise currents can be broken spontaneously. We describe several symmetry-breaking scenarios which imply either restoration of the global condensate rotation or the onset of the circular polarization in the symmetry-broken state.Comment: 9 pages, 5 figure

Light-induced injection of hot carriers from gold nanoparticles to carbon wire bundles

We observed a light-induced enhancement of the tunneling current propagating through an array of parallel carbon chains anchored between gold nanoparticles (NPs). In the presence of laser radiation characterized by a wavelength close to the plasmon resonance of the NPs, the current-voltage characteristics of carbon bundle tunnelling junctions demonstrate a pronounced asymmetry between positive and negative bias values. Such an asymmetry is typical for a Schottky junction, in general. The resistance of the tunnel junction decreases with the increase of the optical pumping intensity. We associate the observed effect with an injection of `hot' carriers created in Au NPs due to the decay of the surface plasmons accompanied by the charge transfer to the carbon bundles. The observed phenomenon can be used for non-resonant excitation of excitonic states in low-dimensional carbon-based structures for single-photon emission, as well as for photovoltaic applications.Comment: 9 pages, 3 figure

Photoluminescence imaging of single photon emitters within nanoscale strain profiles in monolayer WSe2_2

Local deformation of atomically thin van der Waals materials provides a powerful approach to create site-controlled chip-compatible single-photon emitters (SPEs). However, the microscopic mechanisms underlying the formation of such strain-induced SPEs are still not fully clear, which hinders further efforts in their deterministic integration with nanophotonic structures for developing practical on-chip sources of quantum light. Here we investigate SPEs with single-photon purity up to 98% created in monolayer WSe$_2$ via nanoindentation. Using photoluminescence imaging in combination with atomic force microscopy, we locate single-photon emitting sites on a deep sub-wavelength spatial scale and reconstruct the details of the surrounding local strain potential. The obtained results suggest that the origin of the observed single-photon emission is likely related to strain-induced spectral shift of dark excitonic states and their hybridization with localized states of individual defects.Comment: 8 pages, 4 figure

Manipulation of the propagation of light in tunable nonlinear Bragg mirrors with embedded quantum wells

The specially designed nonlinear semiconductor structure with embedded quantum wells possesses a tunable hyperbolic dispersion. We revealed dynamical regimes for localized polariton wave packets resulting from competition of the hyperbolic dispersion and the repulsive nonlinearity.</p