Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Attractive electron-electron interactions from internal screening in
  magic angle twisted bilayer graphene   Twisted bilayer graphene (tBLG) has recently emerged as a new platform for
studying electron correlations, the strength of which can be controlled via the
twist angle. Here, we study the effect of internal screening on
electron-electron interactions in undoped tBLG. Using the random phase
approximation, we find that the dielectric response of tBLG drastically
increases near the magic angle and is highly twist-angle dependent. As a
consequence of the abrupt change of the Fermi velocity as a function of wave
vector, the screened interaction in real space exhibits attractive regions for
certain twist angles near the magic angle. Attractive interactions can induce
charge density waves and superconductivity and therefore our findings could be
relevant to understand the microscopic origins of the recently observed strong
correlation phenomena in undoped tBLG. The resulting screened Hubbard
parameters are strongly reduced and exhibit a non-linear dependence on the
twist angle. We also carry out calculations with the constrained random phase
approximation and parametrize a twist-angle dependent Keldysh model for the
resulting effective interaction.

17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
36
The categories of this paper are: cmp-lg
34
The categories of this paper are: chem-ph
18
The categories of this paper are: econ
14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol
32
The categories of this paper are: atom-ph
11
The categories of this paper are: hep-lat
19
The categories of this paper are: eess
7
The categories of this paper are: hep-th
21
The categories of this paper are: adap-org
10
The categories of this paper are: q-bio
26
The categories of this paper are: bayes-an
2
The categories of this paper are: math
16
The categories of this paper are: stat