66 research outputs found
Tilting flat bands in an empty microcavity
Recently microcavities with anisotropic materials are shown to be able to
create novel bands with non-zero local Berry curvature. The anisotropic
refractive index of the cavity layer is believed to be critical in opening an
energy gap at the tilted Dirac points. In this work, we show that an
anticrossing between a cavity mode and a Bragg mode can also form within an
empty microcavity without any birefringent materials. Flat bands are observed
within the energy gap due to the particular refractive index distribution of
the sample. The intrinsic TE-TM splitting and XY splitting induce the squeezing
of the cavity modes in momentum space, so that the flat bands are
spin-dependently tilted. Our results pave the way to investigate the spin orbit
coupling of photons in a simple microcavity without anisotropic cavity layers
Electrically controlling vortices in a neutral exciton polariton condensate at room temperature
Manipulating bosonic condensates with electric fields is very challenging as
the electric fields do not directly interact with the neutral particles of the
condensate. Here we demonstrate a simple electric method to tune the vorticity
of exciton polariton condensates in a strong coupling liquid crystal (LC)
microcavity with CsPbBr microplates as active material at room temperature.
In such a microcavity, the LC molecular director can be electrically modulated
giving control over the polariton condensation in different modes. For
isotropic non-resonant optical pumping we demonstrate the spontaneous formation
of vortices with topological charges of +1, +2, -2, and -1. The topological
vortex charge is controlled by a voltage in the range of 1 to 10 V applied to
the microcavity sample. This control is achieved by the interplay of a built-in
potential gradient, the anisotropy of the optically active perovskite
microplates, and the electrically controllable LC molecular director in our
system with intentionally broken rotational symmetry. Besides the fundamental
interest in the achieved electric polariton vortex control at room temperature,
our work paves the way to micron-sized emitters with electric control over the
emitted light's phase profile and quantized orbital angular momentum for
information processing and integration into photonic circuits
Single-shot spatial instability and electric control of polariton condensates at room temperature
In planar microcavities, the transverse-electric and transverse-magnetic
(TE-TM) mode splitting of cavity photons arises due to their different
penetration into the Bragg mirrors and can result in optical spin-orbit
coupling (SOC). In this work, we find that in a liquid crystal (LC) microcavity
filled with perovskite microplates, the pronounced TE-TM splitting gives rise
to a strong SOC that leads to the spatial instability of microcavity polariton
condensates under single-shot excitation. Spatially varying hole burning and
mode competition occurs between polarization components leading to different
condensate profiles from shot to shot. The single-shot polariton condensates
become stable when the SOC vanishes as the TE and TM modes are spectrally well
separated from each other, which can be achieved by application of an electric
field to our LC microcavity with electrically tunable anisotropy. Our findings
are well reproduced and traced back to their physical origin by our detailed
numerical simulations. With the electrical manipulation our work reveals how
the shot-to-shot spatial instability of spatial polariton profiles can be
engineered in anisotropic microcavities at room temperature, which will benefit
the development of stable polariton-based optoeletronic and light-emitting
devices
Phenol-Catalyzed Discharge in the Aprotic Lithium-Oxygen Battery
Discharge in the lithiumâO2 battery is known to occur either by a solution mechanism, which enables high capacity and rates, or a surface mechanism, which passivates the electrode surface and limits performance. The development of strategies to promote solutionâphase discharge in stable electrolyte solutions is a central challenge for development of the lithiumâO2 battery. Here we show that the introduction of the protic additive phenol to ethers can promote a solutionâphase discharge mechanism. Phenol acts as a phaseâtransfer catalyst, dissolving the product Li2O2, avoiding electrode passivation and forming large particles of Li2O2 productâvital requirements for high performance. As a result, we demonstrate capacities of over 9â
mAhâcmâ2areal, which is a 35âfold increase in capacity compared to without phenol. We show that the critical requirement is the strength of the conjugate base such that an equilibrium exists between protonation of the base and protonation of Li2O2
Biodegradation of Crystalline and Nonaqueous Phase Liquid-Dissolved ATRAZINE by <i>Arthrobacter</i> sp. ST11 with Cd<sup>2+</sup> Resistance
A newly isolated cadmium (Cd)-resistant bacterial strain from herbicides-polluted soil in China could use atrazine as the sole carbon, nitrogen, and energy source for growth in a mineral salt medium (MSM). Based on 16S rRNA gene sequence analysis and physiochemical tests, the bacterium was identified as Arthrobacter sp. and named ST11. The biodegradation of atrazine by ST11 was investigated in experiments, with the compound present either as crystals or dissolved in di(2-ethylhexyl) phthalate (DEHP) as a non-aqueous phase liquid (NAPL). After 48 h, ST11 consumed 68% of the crystalline atrazine in MSM. After being dissolved in DEHP, the degradation ratio of atrazine was reduced to 55% under the same conditions. Obviously, the NAPL-dissolved atrazine has lower bioavailability than the crystalline atrazine. Cd2+ at concentrations of 0.05â1.5 mmol/L either had no effect (2+ promoted ST11 to degrade atrazine, whether crystalline or dissolved in DEHP. Refusal to adsorb Cd2+ may be the main mechanism of high Cd resistance in ST11 cells. These results may provide valuable insights for the microbial treatment of arable soil co-polluted by atrazine and Cd
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