Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Stable charge density wave phase in a 1T-TiSe$_2$ monolayer   Charge density wave (CDW) phases are symmetry-reduced states of matter in
which a periodic modulation of the electronic charge frequently leads to
drastic changes of the electronic spectrum, including the emergence of energy
gaps. We analyze the CDW state in a 1T-TiSe$_2$ monolayer within a density
functional theory framework and show that, similarly to its bulk counterpart,
the monolayer is unstable towards a commensurate $2{\times}2$ periodic lattice
distortion (PLD) and CDW at low temperatures. Analysis of the electron and
phonon spectrum establishes the PLD as the stable $T=0$ K configuration with a
narrow bandgap, whereas the undistorted and semi-metalic state is stable only
above a threshold temperature. The lattice distortions as well as the unfolded
and reconstructed band structure in the CDW phase agree well with experimental
results. We also address evidence in our results for the role of
electron-electron interactions in the CDW instability of 1T-TiSe$_2$
monolayers.

1
The categories of this paper are: cs
13
The categories of this paper are: quant-ph
16
The categories of this paper are: stat
27
The categories of this paper are: comp-gas
6
The categories of this paper are: astro-ph
15
The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
2
The categories of this paper are: math
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
22
The categories of this paper are: chao-dyn
20
The categories of this paper are: acc-phys
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an