Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Local photo-excitation of shift current in noncentrosymmetric systems   Photocurrent in solids is an important phenomenon with many applications
including the solar cells. In conventional photoconductors, the electrons and
holes created by light irradiation are separated by the external electric
field, resulting in a current flowing into electrodes. Shift current in
noncentrosymmetric systems is distinct from this conventional photocurrent in
the sense that no external electric field is needed, and, more remarkably, is
driven by the Berry phase inherent to the Bloch wavefunction. It is analogous
to the polarization current in the ground state but is a d.c. current
continuously supported by the nonequilibrium steady state under the pumping by
light. Here we show theoretically, by employing Keldysh-Floquet formalism
applied to a simple one-dimensional model, that the local photo excitation can
induce the shift current which is independent of the position and width of the
excited region and also the length of the system. This feature is in stark
contrast to the conventional photocurrent, which is suppressed when the sample
is excited locally at the middle and increases towards the electrodes. This
finding reveals the unconventional nature of shift current and will pave a way
to design a highly efficient photovoltaic effect in solids.

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The categories of this paper are: hep-th
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
32
The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
2
The categories of this paper are: math
25
The categories of this paper are: patt-sol
28
The categories of this paper are: alg-geom
15
The categories of this paper are: nucl-ex
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The categories of this paper are: chao-dyn
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
27
The categories of this paper are: comp-gas