Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Higher-order topological insulators and semimetals in generalized
  Aubry-Andr\'e-Harper models   Higher-order topological phases of matter have been extensively studied in
various areas of physics. While the Aubry-Andr\'e-Harper model provides a
paradigmatic example to study topological phases, it has not been explored
whether a generalized Aubry-Andr\'e-Harper model can exhibit a higher-order
topological phenomenon. Here, we construct a two-dimensional higher-order
topological insulator with chiral symmetry based on the Aubry-Andr\'e-Harper
model. We find the coexistence of zero-energy and nonzero energy
corner-localized modes. The former is protected by the quantized quadrupole
moment, while the latter by the first Chern number of the Wannier band. The
nonzero-energy mode can also be viewed as the consequence of a Chern insulator
localized on a surface. More interestingly, the non-zero energy corner mode can
lie in the continuum of extended bulk states and form a bound state in the
continuum of higher-order topological systems. We finally propose an
experimental scheme to realize our model in electric circuits. Our study opens
a door to further study higher-order topological phases based on the
Aubry-Andr\'e-Harper model.

30
The categories of this paper are: q-alg
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
6
The categories of this paper are: astro-ph
19
The categories of this paper are: eess
17
The categories of this paper are: q-fin
1
The categories of this paper are: cs
26
The categories of this paper are: bayes-an
9
The categories of this paper are: nlin
16
The categories of this paper are: stat
20
The categories of this paper are: acc-phys
18
The categories of this paper are: econ
13
The categories of this paper are: quant-ph
35
The categories of this paper are: mtrl-th
11
The categories of this paper are: hep-lat