Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spin transport in a tunable Heisenberg model realized with ultracold
  atoms   Simple models of interacting spins play an important role in physics. They
capture the properties of many magnetic materials, but also extend to other
systems, such as bosons and fermions in a lattice, systems with gauge fields,
high-Tc superconductors, and systems with exotic particles such as anyons and
Majorana fermions. In order to study and compare these models, a versatile
platform is needed. Realizing such a system has been a long-standing goal in
the field of ultracold atoms. So far, spin transport has only been studied in
the isotropic Heisenberg model. Here we implement the Heisenberg XXZ model with
adjustable anisotropy and use this system to study spin transport far from
equilibrium after quantum quenches from imprinted spin helix patterns. In the
non-interacting XX model, we find ballistic behavior of spin dynamics, while in
the isotropic XXX model, we find diffusive behavior. For positive anisotropies,
the dynamics ranges from anomalous super-diffusion to sub-diffusion depending
on anisotropy, whereas for negative anisotropies, we observe a crossover in the
time domain from ballistic to diffusive transport. This behavior contrasts with
expectations for the linear response regime and raises new questions in
understanding quantum many-body dynamics far away from equilibrium.

9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
35
The categories of this paper are: mtrl-th
29
The categories of this paper are: funct-an
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
25
The categories of this paper are: patt-sol
24
The categories of this paper are: dg-ga
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The categories of this paper are: math-ph
30
The categories of this paper are: q-alg
6
The categories of this paper are: astro-ph
20
The categories of this paper are: acc-phys