S. L. Harrison, A. Nalitov, P. G. Lagoudakis, and H. Sigurðsson Polariton vortex Chern insulator OPTICAL MATERIALS EXPRESS 13, 2550-2562 (2023) https://doi.org/10.1364/OME.494448

We propose a vortex Chern insulator, motivated by recent experimental demonstrations on programmable arrangements of cavity polariton vortices by [S. Alyatkin et al., arXiv, ArXiv:2207.01850 (2022)] and [J. Wang et al, Natl. Sci. Rev. 10, Nwac096 (2022)]. In the absence of any external fields, time-reversal symmetry is spontaneously broken through polariton condensation into structured arrangements of localized co-rotating vortices. We characterize the response of the rotating condensate lattice by calculating the spectrum of Bogoliubov elementary excitations and observe the crossing of edge-states, of opposite vorticity, connecting bands with opposite Chern numbers. The emergent topologically nontrivial energy gap stems from inherent vortex anisotropic polariton-polariton interactions and does not require any spin-orbit coupling, external magnetic fields, or elliptically polarized pump fields.

Septembre, I.; Leblanc, C.; Hermet, L.; Nguyen, H. S.; Letartre, X.; Solnyshkov, D. D.; Malpuech, G. Design of a room-temperature topological exciton-polariton laser in a ZnO/TiO2 photonic crystal slab Phys. Rev. B 107, 155304 (2023) https://doi.org/10.1103/PhysRevB.107.155304

We propose theoretically a scheme to get a room-temperature two-dimensional topological exciton-polariton laser with propagating topological lasing modes. The structure uses guided modes in a photonic crystal slab. A ZnO layer provides strong excitonic resonances stable at room temperature. It is capped by a TiO2 layer pierced by a triangular lattice of air holes. The exciton-polariton modes of the three-dimensional structure are computed by solving numerically Maxwell’s equations including the excitonic response. The designed triangular lattice of circular air holes shows a transverse electric band gap. The triangular lattice of air holes is shown to be well described by a staggered honeycomb tight-binding lattice, associated with valley Chern numbers defining the interface states. The interface between two shifted triangular lattices of air holes supports two counterpropagating modes lying in the gap of the bulk modes, analogous to quantum pseudospin Hall interface states. These modes show orthogonal polarizations. They can be selectively excited using polarized excitation and are well protected from backscattering. These modes can benefit from the exciton-polariton gain at room temperature because of their sufficiently large exciton fraction and favorable position in energy. The strong localization of these propagating modes makes them suitable to host topological lasing triggered by a nonresonant pump localized on the interface.

Septembre, I.; Meyer, J. S.; Solnyshkov, D. D.; Malpuech, G. Weyl singularities in polaritonic multiterminal Josephson junctions Phys. Rev. B 107, 165301 (2023) https://doi.org/10.1103/PhysRevB.107.165301

We study theoretically analog multiterminal Josephson junctions formed by gapped superfluids created upon resonant pumping of cavity exciton polaritons. We study the p-like bands of a five-terminal junction in the four-dimensional (4D) parameter space created by the superfluid phases acting as quasimomenta. We find 4/6 Weyl points in 3D subspaces with preserved/broken time-reversal symmetry. We link the real space topology (vortices) to the parameter space one (Weyl points). We derive an effective Hamiltonian encoding the creation, motion, and annihilation of Weyl nodes in 4D. Our work paves the way to the study of exotic topological phases in a platform allowing direct measurement of eigenstates and band topology.

http://innovation-radar.ec.europa.eu/innovation/49049

The tunable laser wavelength (pulsed). The position of the main emission peak versus the applied voltage. The first series (orange dots) and the second series (purple diamonds) are measured for pulse-energy densities of 2.34 J/cm2 and 3.21 J/cm2, respectively.

Pavel Kokhanchik, Dmitry Solnyshkov, and Guillaume Malpuech Non-Hermitian skin effect induced by Rashba-Dresselhaus spin-orbit coupling Phys. Rev. B 108, L041403 (2023) https://doi.org/10.1103/PhysRevB.108.L041403

One-dimensional (1D) chains with nonreciprocal tunneling realizing the non-Hermitian skin effect (NHSE) have attracted considerable interest in the last years, whereas their experimental realization in real space remains limited to a few examples. In this Letter, we propose a generic way of implementing nonreciprocity based on a combination of Rashba-Dresselhauss spin-orbit coupling, existing for electrons, cold atoms, and photons, and a lifetime imbalance between two spin components. We show that one can realize the Hatano-Nelson model, the non-Hermitian Su-Schrieffer-Heeger model, and even observe the NHSE in a 1D potential well without the need for a lattice. We further demonstrate the practical feasibility of this proposal by considering the specific example of a photonic liquid-crystal microcavity. This platform allows one to switch on and off the NHSE by applying an external voltage to the microcavity.

Gnusov, Ivan; Harrison, Stella; Alyatkin, Sergey; Sitnik, Kirill; Toepfer, Julian; Sigurdsson, Helgi; Lagoudakis, Pavlos SCIENCE ADVANCES 9, eadd1299 (2023) https://doi.org/10.1126/sciadv.add1299

The appearance of quantized vortices in the classical “rotating bucket” experiments of liquid helium and ultracold dilute gases provides the means for fundamental and comparative studies of different superfluids. Here, we realize the rotating bucket experiment for optically trapped quantum fluid of light based on exciton-polariton Bose-Einstein condensate in semiconductor microcavity. We describe the phenomenology using the generalized Gross-Pitaevskii equation. Our results enable the study of polariton superfluidity on a par with other superfluids, as well as deterministic, all-optical control over structured nonlinear light.

Krzysztof Tyszka, Magdalena Furman, Rafał Mirek, Mateusz Król, Andrzej Opala, Bartłomiej Seredyński, Jan Suffczyński, Wojciech Pacuski, Michał Matuszewski, Jacek Szczytko, Barbara Piętka Leaky Integrate-and-Fire Mechanism in Exciton–Polariton Condensates for Photonic Spiking Neurons Laser Photonics Rev.2023, 17, 2100660 https://doi.org/10.1002/lpor.202100660

S. L. Harrison, H. Sigurdsson, and P. G. Lagoudakis Minor embedding with Stuart-Landau oscillator networks Phys. Rev. Research 5, 013018 https:/doi.org/10.1103/PhysRevResearch.5.013018

We theoretically implement a strategy from quantum computation architectures to simulate Stuart-Landau oscillator dynamics in all-to-all connected networks, also referred to as complete graphs. The technique builds upon the triad structure minor embedding which expands dense graphs of interconnected elements into sparse ones which can potentially be realized in future on-chip solid-state technologies with tunable edge weights. As a case study, we reveal that the minor embedding procedure allows simulating the XY model on complete graphs, thus bypassing a severe geometric constraint.

Jianbo De, Xuekai Ma, Fan Yin, Jiahuan Ren, Jiannian Yao, Stefan Schumacher, Qing Liao, Hongbing Fu, Guillaume Malpuech, and Dmitry Solnyshkov Room-Temperature Electrical Field-Enhanced Ultrafast Switch in Organic Microcavity Polariton Condensates J. Am. Chem. Soc (2023) https://pubs.acs.org/doi/10.1021/jacs.2c07557

We demonstrate a significant improvement of emitted intensity and condensation threshold by applying an electric field to a microcavity filled with an organic microbelt. Our theoretical investigations indicate that the electric field makes the excitons dipolar and induces an enhancement of the exciton–polariton interaction and of the polariton lifetime. Based on these electric field-induced changes, a sub-nanosecond electrical field-enhanced polariton condensate switch is realized at room temperature, providing the basis for developing an on-chip integrated photonic device in the strong light–matter coupling regime.

Zhaoyang Zhang, Yuan Feng, Feng Li, Sergei Koniakhin, Changbiao Li, Fu Liu, Yanpeng Zhang, Min Xiao, Guillaume Malpuech, and Dmitry Solnyshkov Angular-Dependent Klein Tunneling in Photonic Graphene Phys. Rev. Lett. 129, 233901 https://doi.org/10.1103/PhysRevLett.129.233901

The Klein paradox consists in the perfect tunneling of relativistic particles through high potential barriers. It is responsible for the exceptional conductive properties of graphene. While in theory the perfect tunneling holds only for normal incidence, so far the angular dependence of the Klein tunneling and its strong variation with the barrier height were not measured experimentally. In this Letter, we capitalize on the versatility of atomic vapor cells with paraxial beam propagation and index patterning by electromagnetically induced transparency. We report the first experimental observation of perfect Klein transmission in a 2D photonic system (photonic graphene) at normal incidence and measure the angular dependence. Counterintuitively, but in agreement with the Dirac equation, we observe that the decay of the Klein transmission versus angle is suppressed by increasing the barrier height, a key result for the conductivity of graphene and its analogs.