  Using one-dimensional spin-1/2 systems as prototypes of quantum many-body
systems, we study the emergence of quantum chaos. The main purpose of this work
is to answer the following question: how does the spin-orbit interaction, as a
pure quantum interaction, may lead to the onset of quantum chaos? We consider
three integrable spin-1/2 systems: the Ising, the XX, and the XXZ limits, and
analyze whether quantum chaos develops or not after the addition of the
Dzyaloshinskii-Moriya interaction. We find that, depending on the strength of
the anisotropy parameter, the answer is positive for the XXZ and Ising models,
while no such evidence is observed for the XX model. We also discuss the
relationship between quantum chaos and thermalization.
