Recent experimental and theoretical results show that weakly interacting
atomic Bose-Bose mixtures with attractive interspecies interaction are
stabilized by beyond-mean-field effects. Here we consider the peculiar
properties of these systems in a strictly one-dimensional configuration, taking
also into account the nontrivial role of spin-orbit and Rabi couplings. We show
that when the value of inter- and intraspecies interaction strengths are such
that mean-field contributions to the energy cancel, a self-bound bright soliton
fully governed by quantum fluctuations exists. We derive the phase diagram of
the phase transition between a single-peak soliton and a multipeak (striped)
soliton, produced by the interplay between spin-orbit, Rabi couplings and
beyond-mean-field effects, which also affect the breathing mode frequency of
the atomic cloud. Finally, we prove that a phase imprinting of the single-peak
soliton leads to a self-confined propagating solitary wave even in the presence
of spin-orbit coupling.Comment: 6 pages, 4 figures, published in Phys. Rev.
