Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hofstadter Butterfly in Graphene   This is a short review of the recent progresses on Hofstadter butterfly in
graphene, organized in the following. We first briefly introduce the Hofstadter
butterfly, including the theoretic toy model of Bloch electrons in the magnetic
field, the resulting Harper's equation and its solution, and realizations in
non-graphene systems. Then, we discuss the ways to realize the fractal
Hofstadter spectra in graphene, and introduce three types of graphene
superlattice structure, including graphene-hBN, twisted graphene layers,
nanofabricated graphene superlattice. In particular, details about the fractal
Hofstadter spectrum in graphene will be focused and discussed in the
graphene-hBN superlattice and the twisted bilayer graphene.

13
The categories of this paper are: quant-ph
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
36
The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: nlin
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The categories of this paper are: adap-org
2
The categories of this paper are: math