Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Wannier-Stark states in double-periodic lattices II: two-dimensional
  lattices   We analyze the Wannier-Stark spectrum of a quantum particle in tilted
two-dimensional lattices with the Bloch spectrum consisting of two subbands,
which could be either separated by a finite gap or connected at the Dirac
points. For rational orientations of the static field given by an arbitrary
superposition of the translation vectors the spectrum is a ladder of energy
bands. We obtain asymptotic expressions for the energy bands in the limit of
large and weak static fields and study them numerically for intermediate field
strength. We show that the structure of energy bands determines the rate of
spreading of a localized wave packets which is the quantity measured in
laboratory experiments. It is shown that wave-packet dispersion becomes a
fractal function of the field orientation in the long-time regime of ballistic
spreading.

28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
15
The categories of this paper are: nucl-ex
26
The categories of this paper are: bayes-an
30
The categories of this paper are: q-alg
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
2
The categories of this paper are: math
14
The categories of this paper are: math-ph
21
The categories of this paper are: adap-org
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
12
The categories of this paper are: nucl-th