Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Interacting Polaron-Polaritons   Two dimensional semiconductors provide an ideal platform for exploration of
linear exciton and polariton physics, primarily due to large exciton binding
energy and strong light-matter coupling. These features, however, generically
imply reduced exciton-exciton interactions, hindering the realisation of active
optical devices such as lasers or parametric oscillators. Here, we show that
electrical injection of itinerant electrons into monolayer molybdenum
diselenide allows us to overcome this limitation: dynamical screening of
exciton-polaritons by electrons leads to the formation of new quasi-particles
termed polaron-polaritons that exhibit unexpectedly strong interactions as well
as optical amplification by Bose-enhanced polaron-electron scattering. To
measure the nonlinear optical response, we carry out time-resolved pump-probe
measurements and observe polaron-polariton interaction enhancement by a factor
of 50 ($0.5 \mu$eV $\mu$m$^2$) as compared to exciton-polaritons. Concurrently,
we measure a spectrally integrated transmission gain of the probe field of
$\gtrsim 2$ stemming from stimulated scattering of polaron-polaritons. We show
theoretically that the non-equilibrium nature of optically excited
quasiparticles favours a previously unexplored interaction mechanism stemming
from a phase-space filling in the screening cloud, which provides an accurate
explanation of the strong repulsive interactions observed experimentally. Our
findings show that itinerant electron-exciton interactions provide an
invaluable tool for electronic manipulation of optical properties, demonstrate
a new mechanism for dramatically enhancing polariton-polariton interactions,
and pave the way for realisation of nonequilibrium polariton condensates.

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The categories of this paper are: q-bio
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The categories of this paper are: acc-phys
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The categories of this paper are: chem-ph
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The categories of this paper are: stat
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The categories of this paper are: alg-geom
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The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: quant-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-ph
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The categories of this paper are: hep-lat