Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electrically switchable Berry curvature dipole in the monolayer
  topological insulator WTe2   Recent experimental evidence for the quantum spin Hall (QSH) state in
monolayer WTe$_2$ has bridged two of the most active fields of condensed matter
physics, 2D materials and topological physics. This 2D topological crystal also
displays unconventional spin-torque and gate-tunable superconductivity. While
the realization of QSH has demonstrated the nontrivial topology of the electron
wavefunctions of monolayer WTe$_2$, the geometrical properties of the
wavefunction, such as the Berry curvature, remain unstudied. On the other hand,
it has been increasingly recognized that the Berry curvature plays an important
role in multiple areas of condensed matter physics including nonreciprocal
electron transport, enantioselective optical responses, chiral polaritons and
even unconventional superconductivity. Here we utilize mid-infrared
optoelectronic microscopy to investigate the Berry curvature in monolayer
WTe$_2$. By optically exciting electrons across the inverted QSH gap, we
observe an in-plane circular photogalvanic current even under normal incidence.
The application of an out-of-plane displacement field further systematically
controls the direction and magnitude of the photocurrent. Our observed
photocurrent reveals a novel Berry curvature dipole that arises from the
nontrivial wavefunctions near the inverted gap edge. These previously
unrealized Berry curvature dipole and strong electric field effect are uniquely
enabled by the inverted band structure and tilted crystal lattice of monolayer
WTe$_2$. Such an electrically switchable Berry curvature dipole opens the door
to the observation of a wide range of quantum geometrical phenomena, such as
quantum nonlinear Hall, orbital-Edelstein and chiral polaritonic effects.

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The categories of this paper are: alg-geom
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The categories of this paper are: solv-int
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The categories of this paper are: chem-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: adap-org
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The categories of this paper are: chao-dyn
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The categories of this paper are: physics
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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: nlin
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The categories of this paper are: hep-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: quant-ph
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The categories of this paper are: econ
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The categories of this paper are: acc-phys