Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Review of annealing effects and superconductivity in
  Fe$_{1+y}$Te$_{1-x}$Se$_x$ superconductors   Fe$_{1+y}$Te$_{1-x}$Se$_x$ is unique in their structural simplicity,
consisting of only FeTe/Se layers, which is favorable for probing the mechanism
of superconductivity. Recently, a topological surface superconductivity as well
as the Majorana Fermions has been observed, which makes
Fe$_{1+y}$Te$_{1-x}$Se$_x$ the first high temperature topological
superconductor. Since large size single crystal of Fe$_{1+y}$Te$_{1-x}$Se$_x$
can be easily grown, many researches have been performed. However, a large part
of the reported results are under controversy, including the resistivity,
susceptibility, Hall effect, gap structure, phase diagram, etc. These
controversies are believed to come from the sample-dependent Fe
nonstoichiometries, which originate from the partial occupation of the second
Fe site (excess Fe) in the Te/Se layer. The excess Fe with valence near Fe$^+$
will provide electron doping into the system. Meanwhile, the excess Fe is also
strongly magnetic, which will act as a paring breaker and also localize the
charge carriers. Removing the excess Fe is essential to probe the intrinsic
properties and mechanism of superconductivity of Fe$_{1+y}$Te$_{1-x}$Se$_x$
compounds. In this topical review, we propose the effective approaches to
remove excess Fe in Fe$_{1+y}$Te$_{1-x}$Se$_x$. Furthermore, we discuss the
mechanism of annealing based on the evolutions of structure, composition, and
morphology with annealing. Moreover, we also review the annealing effects on
the normal state and superconducting properties, including the magnetism,
transport properties, band structure, $T_{\rm{c}}$, phase diagram, upper
critical field, anisotropy, critical current density, gap structure, and
superconducting pairing. This review presents not only the optimal way to
prepare crystals without excess Fe, but also the intrinsic properties of
Fe$_{1+y}$Te$_{1-x}$Se$_x$ without the influence of excess Fe.

14
The categories of this paper are: math-ph
7
The categories of this paper are: hep-th
13
The categories of this paper are: quant-ph
20
The categories of this paper are: acc-phys
25
The categories of this paper are: patt-sol
11
The categories of this paper are: hep-lat
8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
29
The categories of this paper are: funct-an
5
The categories of this paper are: gr-qc
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int
18
The categories of this paper are: econ
19
The categories of this paper are: eess
17
The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph