Dipolar bosons in one dimension: the case of longitudinal dipole alignment

We study by quantum Monte Carlo simulations the low-temperature phase diagram of dipolar bosons confined to one dimension, with dipole moments aligned along the direction of particle motion. A hard core repulsive potential of varying range ($\sigma$) is added to the dipolar interaction, in order to ensure stability of the system against collapse. In the $\sigma\to 0$ limit the physics of the system is dominated by the potential energy and the ground state is quasi-crystalline; as $\sigma$ is increased the attractive part of the interaction weakens and the equilibrium phase evolves from quasi-crystalline to a non-superfluid liquid. At a critical value $\sigma_c$, the kinetic energy becomes dominant and the system undergoes a quantum phase transition from a self-bound liquid to a gas. In the gaseous phase with $\sigma\to\sigma_c$, at low density attractive interactions bring the system into a "weak" superfluid regime. However, gas-liquid coexistence also occurs, as a result of which the topologically protected superfluid regime is not approached.