Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evidence of nematic order and nodal superconducting gap along [110]
  direction in RbFe2As2   Unconventional superconductivity often intertwines with various forms of
order, such as the "nematic" order which breaks the rotational symmetry of the
lattice. Investigation of these ordered phases sheds crucial light on the
superconductivity itself. Here we report a low-temperature scanning tunneling
microscopy (STM) study on RbFe2As2, a heavily hole-doped Fe-based
superconductor (FeSC). We observe significant symmetry breaking in its
electronic structure and magnetic vortex which differentiates the ({\pi},
{\pi}) and ({\pi}, -{\pi}) directions of the unfolded Brillouin zone (BZ). It
is thus a novel nematic state, distinct from the nematicity of
undoped/lightly-doped FeSCs which breaks the ({\pi}, 0) / (0, {\pi})
equivalence. Moreover, we observe a clear "V"-shaped superconducting gap which
can be well fitted with a nodal gap function. The gap is found to be suppressed
on surface Rb vacancies and at step edges, and the suppression is particularly
strong at the [110]-oriented edges. This is possibly due to a dx2-y2 like
pairing component with nodes along the [110] directions. We further
demonstrated that such ({\pi}, {\pi}) nematic state can be suppressed via
surface electron doping to RbFe2As2, and the superconductivity is subsequently
enhanced. Our results thus highlight the intimate connection between nematicity
and superconducting pairing in iron-based superconductors.

37
The categories of this paper are: supr-con
11
The categories of this paper are: hep-lat
0
The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
21
The categories of this paper are: adap-org
8
The categories of this paper are: hep-ex
20
The categories of this paper are: acc-phys
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
32
The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
16
The categories of this paper are: stat