Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Mixed-valence insulators with neutral Fermi surfaces   Samarium hexaboride is a classic three-dimensional mixed valence system with
a high-temperature metallic phase that evolves into a paramagnetic charge
insulator below 40 kelvin. A number of recent experiments have suggested the
possibility that the low-temperature insulating bulk hosts electrically neutral
gapless fermionic excitations. Here we show that a possible ground state of
strongly correlated mixed valence insulators - composite exciton Fermi liquid -
hosts a three dimensional Fermi surface of a neutral fermion, that we name the
"composite exciton". We describe the mechanism responsible for the formation of
such excitons, discuss the phenomenology of the composite exciton Fermi liquids
and make comparison to experiments in SmB$_6$.

16
The categories of this paper are: stat
31
The categories of this paper are: ao-sci
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
23
The categories of this paper are: solv-int
3
The categories of this paper are: physics
0
The categories of this paper are: hep-ph
28
The categories of this paper are: alg-geom
18
The categories of this paper are: econ
9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
27
The categories of this paper are: comp-gas
7
The categories of this paper are: hep-th
10
The categories of this paper are: q-bio