Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Incoherent population mixing contributions to phase-modulation
  two-dimensional coherent excitation spectra   We present theoretical and experimental results showing the effects of
incoherent population mixing on two-dimensional (2D) coherent excitation
spectra that are measured via a time-integrated population and phase-sensitive
detection. The technique uses four collinear ultrashort pulses and phase
modulation to acquire two-dimensional spectra by isolating specific nonlinear
contributions to the photoluminescence or photocurrent excitation signal. We
demonstrate that an incoherent contribution to the measured lineshape, arising
from nonlinear population dynamics over the entire photoexcitation lifetime,
generates a similar lineshape to the expected 2D coherent spectra in
condensed-phase systems. In those systems, photoexcitations are mobile such
that inter-particle interactions are important on any timescale, including
those long compared to the 2D coherent experiment. Measurements on a
semicrystalline polymeric semiconductor film at low temperature show that, in
some conditions in which multi-exciton interactions are suppressed, the
technique predominantly detects coherent signal and can be used, in our
example, to extract homogeneous linewidths. The same method used on a
lead-halide perovskite photovoltaic cell shows that incoherent population
mixing of mobile photocarriers can dominate the measured signal since
carrier-carrier bimolecular scattering is active even at low excitation
densities, which hides the coherent contribution to the spectral lineshape.

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The categories of this paper are: mtrl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: alg-geom
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The categories of this paper are: math-ph
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The categories of this paper are: funct-an
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The categories of this paper are: q-fin
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The categories of this paper are: adap-org
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The categories of this paper are: cmp-lg
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The categories of this paper are: gr-qc
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The categories of this paper are: chao-dyn
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The categories of this paper are: math
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The categories of this paper are: chem-ph
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The categories of this paper are: hep-th
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The categories of this paper are: hep-ex
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The categories of this paper are: astro-ph
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The categories of this paper are: quant-ph