Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Orbital order phase transition in $Pr_{1-x}Ca_xMnO_3$ probed by
  photovoltaics   The phase diagram of $Pr_{1-x}Ca_xMnO_3$ is modified x $\le$ 0.3, which
suggests a reevaluation of the phase diagram of other manganites in that doping
region. Rather than an orbital ordered phase reaching up to high temperatures
of approximately 800-1100 K, we propose a loss of spontaneous orbital order
already near room temperature. Above this temperature, the phase is
characterized by a finite orbital polarization and octahedral tilt pattern. The
tilt pattern couples to the Jahn-Teller distortion and thus induces a remaining
orbital order, which persists up to high temperatures, where the tilt order is
lost as well. This explains the experimental observation of orbital order up to
high temperatures. The reevaluation of the orbital order transition is based on
observed anomalies of various physical properties at a temperatures of 220-260
K in epitaxial thin films of $Pr_{1-x}Ca_xMnO_3$ x=0.1, i.e.in the photovoltaic
effect, electric transport, magnetization, optical and ultrafast transient pump
probe studies. Finite-temperature simulations based on a tight-binding model
with carefully adjusted parameters from first-principles calculations exhibit
an orbital order phase transition at $T_{OO} \approx$ 300 K for x=0.1. This is
consistent with the experimental observation of a temperature dependent change
in lattice parameter for bulk samples of the same doping at 300 K for x=0.1 and
350 K for x=0, typical for a second order phase transition. Since our
reassignment of the orbital order phase transition towards lower temperatures
challenges a well-established and long-accepted picture, we provide results of
multiple complementary measurements as well as a detailed discussion.

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The categories of this paper are: q-alg
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The categories of this paper are: nucl-ex
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The categories of this paper are: nucl-th
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The categories of this paper are: comp-gas
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The categories of this paper are: mtrl-th
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The categories of this paper are: funct-an
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The categories of this paper are: atom-ph
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The categories of this paper are: math-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: acc-phys
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The categories of this paper are: dg-ga
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The categories of this paper are: solv-int
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The categories of this paper are: q-bio
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The categories of this paper are: nlin
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The categories of this paper are: hep-th
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The categories of this paper are: math