Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Terahertz pulse-driven collective mode in the nematic superconducting
  state of Ba$_{1-x}$K$_x$Fe$_2$As$_2$   We investigate the iron-based superconductor Ba$_{1-x}$K$_x$Fe$_2$As$_2$
using intense terahertz (THz) light. In the superconducting state a THz Kerr
signal is observed and assigned to non-linear THz coupling to superconducting
degrees of freedom. The polarization dependence of the THz Kerr signal is
remarkably sensitive to the coexistence of a nematic order. In the absence of
nematic order the $C_4$ symmetric polarization dependence of the THz Kerr
signal is consistent with a coupling to the Higgs amplitude mode of the
superconducting condensate. In the coexisting nematic and superconducting state
the signal becomes purely nematic with a vanishing $C_4$ symmetric component,
signaling the emergence of a new superconducting collective mode activated by
nematicity.

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The categories of this paper are: q-fin
26
The categories of this paper are: bayes-an
29
The categories of this paper are: funct-an
15
The categories of this paper are: nucl-ex
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
13
The categories of this paper are: quant-ph
32
The categories of this paper are: atom-ph
33
The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
28
The categories of this paper are: alg-geom
8
The categories of this paper are: hep-ex