Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Signature of an Ultrafast Photo-Induced Lifshitz Transition in the
  Nodal-Line Semimetal ZrSiTe   Here we report an ultrafast optical spectroscopic study of the nodal-line
semimetal ZrSiTe. Our measurements reveal that, converse to other compounds of
the family, the sudden injection of electronic excitations results in a
strongly coherent response of an $A_{1g}$ phonon mode which dynamically
modifies the distance between Zr and Te atoms and Si layers. "Frozen phonon"
DFT calculations, in which band structures are calculated as a function of
nuclear position along the phonon mode coordinate, show that large
displacements along this mode alter the material's electronic structure
significantly, forcing bands to approach and even cross the Fermi energy. The
incoherent part of the time domain response reveals that a delayed electronic
response at low fluence discontinuously evolves into an instantaneous one for
excitation densities larger than $3.43 \times 10^{17}$ cm$^{-3}$. This sudden
change of the dissipative channels for electronic excitations is indicative of
an ultrafast Lifshitz transition which we tentatively associate to a change in
topology of the Fermi surface driven by a symmetry preserving $A_{1g}$ phonon
mode.

1
The categories of this paper are: cs
34
The categories of this paper are: chem-ph
35
The categories of this paper are: mtrl-th
30
The categories of this paper are: q-alg
22
The categories of this paper are: chao-dyn
19
The categories of this paper are: eess
25
The categories of this paper are: patt-sol
21
The categories of this paper are: adap-org
14
The categories of this paper are: math-ph
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
28
The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
20
The categories of this paper are: acc-phys
7
The categories of this paper are: hep-th