Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Polar Kerr Effect as Probe for Time-Reversal Symmetry Breaking in
  Unconventional Superconductors   The search for broken time reversal symmetry (TRSB) in unconventional
superconductors intensified in the past year as more systems have been
predicted to possess such a state. Following our pioneering study of TRSB
states in Sr$_2$RuO$_4$ using magneto-optic probes, we embarked on a systematic
study of several other of these candidate systems. The primary instrument for
our studies is the Sagnac magneto-optic interferometer, which we recently
developed. This instrument can measure magneto-optic Faraday or Kerr effects
with an unprecedented sensitivity of 10 nanoradians at temperatures as low as
100 mK. In this paper we review our recent studies of TRSB in several systems,
emphasizing the study of the pseudogap state of high temperature
superconductors and the inverse proximity effect in superconductor/ferromagnet
proximity structures.

1
The categories of this paper are: cs
16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th
32
The categories of this paper are: atom-ph
24
The categories of this paper are: dg-ga
28
The categories of this paper are: alg-geom
14
The categories of this paper are: math-ph
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
17
The categories of this paper are: q-fin
8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph
22
The categories of this paper are: chao-dyn
27
The categories of this paper are: comp-gas
3
The categories of this paper are: physics