## Path Integral Monte Carlo study of ultra cold atoms with dipolar moment in a harmonic trap    [PDF]

Michele Ruggeri
In this work we study a system of Bose particles with finite dipole moment in a harmonic trap; in particular we consider a system in which the direction of the dipoles is fixed by an external field. Our computations are performed using Path Integral Monte Carlo, an exact, finite temperature Quantum Monte Carlo technique. The samplings are performed in the Grand Canonical ensemble, using the Worm algorithm. We evaluate the density of the dipoles inside the trap and the radial pair correlation function, as functions of the tilt angle \Theta\ between the dipoles and the x axis. We compare the behaviour of the quantum system and the classical one. We also show the energy per particle and the superfluid fraction. We explore the region between \Theta=55{\deg} and \Theta=90{\deg}, where the system is stable. Systems of different size are studied. We observe that a small \Theta\ hinders the superfluidity and favours the formation of stripes, while for large \Theta\ concentric shells can be observed. Analogue structures can be observed in the classical system at finite temperature.
View original: http://arxiv.org/abs/1305.6007