Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optical spectroscopy of plasmons and excitons in cuprate superconductors   An introduction is given to collective modes in layered, high Tc
superconductors. An experimental demonstration is treated of the mechanism
proposed by Anderson whereby photons travelling inside the superconductor
become massive, when the U(1) gauge symmetry is broken in the superconductor to
which the photons are coupled. Using the Ferrell-Tinkham sumrule the photon
mass is shown to have a simple relation to the spectral weight of the
condensate. Various forms of Josephson plasmons can exist in single-layer, and
bi-layecuprates. In the bi-layer cuprates a transverse optical plasma mode can
be observed as a peak in the c-axis optical conductivity. This mode appears as
a consequence of the existence of two different intrinsic Josephson couplings
between the CuO2 layers. It is strongly related to a collective oscillation
corresponding to small fluctuations of the relative phases of the two
condensates, which has been predicted in 1966 by A.J. Leggett for
superconductors with two bands of charge carriers. A description is given of
optical data of the high Tc cuprates demonstrating the presence of these and
similar collective modes.

37
The categories of this paper are: supr-con
6
The categories of this paper are: astro-ph
14
The categories of this paper are: math-ph
9
The categories of this paper are: nlin
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
33
The categories of this paper are: plasm-ph
13
The categories of this paper are: quant-ph
24
The categories of this paper are: dg-ga
18
The categories of this paper are: econ
29
The categories of this paper are: funct-an
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
25
The categories of this paper are: patt-sol
8
The categories of this paper are: hep-ex
32
The categories of this paper are: atom-ph