Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Low-frequency Raman scattering in WSe$_2$-MoSe$_2$ heterobilayers:
  Evidence for atomic reconstruction   We investigate WSe$_2$-MoSe$_2$ heterobilayers with different twist angles
$\theta \pm \delta$ between the two layers, by low-frequency Raman scattering.
In sufficiently aligned samples with $\theta=0^\circ$, or $\theta=60^\circ$,
and $\delta \lesssim 3^\circ$, we observe an interlayer shear mode (ISM), which
is a clear sign of a commensurate bilayer structure, i.e., the layers must
undergo an atomic reconstruction to form R-type or H-type stacking orders. We
find slightly different ISM energies of about 18~cm$^{-1}$ and 17~cm$^{-1}$ for
H-type and R-type reconstructions, respectively, independent of the exact value
of $\theta\pm \delta$. Our findings are corroborated by the fact that the ISM
is not observed in samples with twist angles, which deviate by $\delta >
3^\circ$ from $0^\circ$ or $60^\circ$. This is expected, since in such
incommensurate structures, with the possibility of
Moir$\acute{\text{e}}$-lattice formation, there is no restoring force for an
ISM. Furthermore, we observe the ISM even in sufficiently aligned
heterobilayers, which are encapsulated in hexagonal Boron nitride. This is
particularly relevant for the characterization of high-quality heterostructure
devices.

7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
3
The categories of this paper are: physics
5
The categories of this paper are: gr-qc
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
13
The categories of this paper are: quant-ph
15
The categories of this paper are: nucl-ex
23
The categories of this paper are: solv-int
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys
19
The categories of this paper are: eess