Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Finite-temperature density-matrix renormalization group method for
  electron-phonon systems: Thermodynamics and Holstein-polaron spectral
  functions   We investigate the thermodynamics and finite-temperature spectral functions
of the Holstein polaron using a density-matrix renormalization group method.
Our method combines purification and local basis optimization (LBO) as an
efficient treatment of phonon modes. LBO is a scheme which relies on finding
the optimal local basis by diagonalizing the local reduced density matrix. By
transforming the state into this basis, one can truncate the local Hilbert
space with a negligible loss of accuracy for a wide range of parameters. In
this work, we focus on the crossover regime between large and small polarons of
the Holstein model. Here, no analytical solution exists and we show that the
thermal expectation values at low temperatures are independent of the phonon
Hilbert space truncation provided the basis is chosen large enough. We then
demonstrate that we can extract the electron spectral function and establish
consistency with results from a finite-temperature Lanczos method. We
additionally calculate the electron emission spectrum and the phonon spectral
function and show that all the computations are significantly simplified by the
local basis optimization. We observe that the electron emission spectrum shifts
spectral weight to both lower frequencies and larger momenta as the temperature
is increased. The phonon spectral function experiences a large broadening and
the polaron peak at large momenta gets significantly flattened and merges
almost completely into the free-phonon peak.

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The categories of this paper are: hep-th
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The categories of this paper are: math-ph
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The categories of this paper are: supr-con
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The categories of this paper are: hep-ph
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The categories of this paper are: nlin
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The categories of this paper are: hep-ex
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The categories of this paper are: econ
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The categories of this paper are: ao-sci
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The categories of this paper are: q-alg
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The categories of this paper are: alg-geom
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The categories of this paper are: bayes-an
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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: mtrl-th
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The categories of this paper are: astro-ph
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The categories of this paper are: patt-sol