123 research outputs found
Direct observation of split-mode exciton-polaritons in a single MoS nanotube
A single nanotube synthesized from a transition metal dichalcogenide (TMDC)
exhibits strong exciton resonances and, in addition, can support optical
whispering gallery modes. This combination is promising for observing
exciton-polaritons without an external cavity. However, traditional
energy-momentum-resolved detection methods are unsuitable for this tiny object.
Instead, we propose to use split optical modes in a twisted nanotube with the
flattened cross-section, where a gradually decreasing gap between the opposite
walls leads to a change in mode energy, similar to the effect of the barrier
width on the eigenenergies in the double-well potential. Using
micro-reflectance spectroscopy, we investigated the rich pattern of polariton
branches in single MoS tubes with both variable and constant gaps. Observed
Rabi splitting in the 40 - 60 meV range is comparable to that for a MoS
monolayer in a microcavity. Our results, based on the polariton dispersion
measurements and polariton dynamics analysis, present a single TMDC nanotube as
a perfect polaritonic structure for nanophotonics
Twisted Nanotubes of Transition Metal Dichalcogenides with Split Optical Modes for Tunable Radiated Light Resonators
Synthesized micro- and nanotubes composed of transition metal dichalcogenides
(TMDCs) such as MoS are promising for many applications in nanophotonics,
because they combine the abilities to emit strong exciton luminescence and to
act as whispering gallery microcavities even at room temperature. In addition
to tubes in the form of hollow cylinders, there is an insufficiently-studied
class of twisted tubes, the flattened cross section of which rotates along the
tube axis. As shown by theoretical analysis, in such nanotubes the interaction
of electromagnetic waves excited at opposite sides of the cross section can
cause splitting of the whispering gallery modes. By studying
micro-photoluminescence spectra measured along individual MoS tubes, it has
been established that the splitting value, which controls the energies of the
split modes, depends exponentially on the aspect ratio of the cross section,
which varies in "breathing" tubes, while the relative intensity of the modes in
a pair is determined by the angle of rotation of the cross section. These
results open up the possibility of creating multifunctional tubular TMDC
nanodevices that provide resonant amplification of self-emitting light at
adjustable frequencies
Cl Anion-Dependent Mg-ATPase
We studied, in the rat brain, the synaptosomal and microsomal membrane fractions of Clâ ion-activated, Mg2+-dependent ATPase, satisfying the necessary kinetic peculiarities of transport ATPases, by a novel method of kinetic analysis of the multisite enzyme systems: (1) the [Mg-ATP] complex constitutes the substrate of the enzymic reaction; (2) the VÂ =Â f(Clâ) dependence-reflecting curve is bell-shaped; (3) substrate dependence, VÂ =Â f(S), curves at a constant concentration of free ligands (Mgf, ATPf, Clâ); (4) as known from the literature, in the process of reaction a phosphorylated intermediate is formed (Gerencser, Crit Rev Biochem Mol Biol 31:303â337, 1996). We report on the Cl-ATPase molecular mechanism and its place in the âP-type ATPaseâ classification
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