Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optical excitations in compressible and incompressible two-dimensional
  electron liquids   Optically generated electron-hole pairs can probe strongly correlated
electronic matter, or, by forming exciton-polaritons within an optical cavity,
give rise to photonic nonlinearities. The present paper theoretically studies
the properties of electron-hole pairs in a two-dimensional electron liquid in
the fractional quantum Hall regime. In particular, we quantify the effective
interactions between optical excitations by numerically evaluating the system's
energy spectrum under the assumption of full spin and Landau level
polarization. Optically most active are those pair excitations which do not
modify the correlations of the electron liquid, also known as multiplicative
states. In the case of spatial separation of electrons and holes, these
excitations interact repulsively with each other. However, when the electron
liquid is compressible, other non-multiplicative configurations occur at lower
energies. The interactions of such dark excitations strongly depend on the
liquid, and can also become attractive. For the case of a single excitation, we
also study the effect of Landau level mixing in the valence band which can
dramatically change the effective mass of an exciton.

19
The categories of this paper are: eess
1
The categories of this paper are: cs
29
The categories of this paper are: funct-an
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
2
The categories of this paper are: math
17
The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
6
The categories of this paper are: astro-ph
23
The categories of this paper are: solv-int
33
The categories of this paper are: plasm-ph
25
The categories of this paper are: patt-sol
20
The categories of this paper are: acc-phys
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin