Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Lattice relaxation and energy band modulation in twisted bilayer
  graphenes   We theoretically study the lattice relaxation in the twisted bilayer graphene
(TBG) and its effect on the electronic band structure. We develop an effective
continuum theory to describe the lattice relaxation in general TBGs and obtain
the optimized structure to minimize the total energy. At small rotation angles
$< 2^{\circ}$, in particular, we find that the relaxed lattice drastically
reduces the area of AA-stacking region, and form a triangular domain structure
with alternating AB and BA stacking regions. We then investigate the effect of
the domain formation on the electronic band structure. The most notable change
from the non-relaxed model is that an energy gap up to 20meV opens at the
superlattice subband edges on the electron and hole sides. We also find that
the lattice relaxation significantly enhances the Fermi velocity, which was
strongly suppressed in the non-relaxed model.

23
The categories of this paper are: solv-int
27
The categories of this paper are: comp-gas
29
The categories of this paper are: funct-an
21
The categories of this paper are: adap-org
8
The categories of this paper are: hep-ex
37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
3
The categories of this paper are: physics
25
The categories of this paper are: patt-sol
36
The categories of this paper are: cmp-lg
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
22
The categories of this paper are: chao-dyn
15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin
12
The categories of this paper are: nucl-th