Confinement-induced quantum melting and polarization cooling for a 2D dipolar crystal

¹ Physics Department, University of Maryland - College Park, MD 20740, USA
² Physics Department, National Tsing-Hua University - Hsinchu 300, Taiwan, ROC
³ Physics Division, National Center for Theoretical Science - Hsinchu, Taiwan, ROC

^a dwwang@phys.nthu.edu.tw

Received: 3 October 2009
Accepted: 7 September 2010

Abstract

We investigate the confinement effects on a two-dimensional mesoscopic (particle number N>200) self-assembled dipolar crystal trapped in a harmonic potential. The ground-state wave function and energy are calculated by diagonalizing the position fluctuations to the quadratic order within the strong-interaction limit. We further investigate the crystal-liquid domain wall boundary as well as the system temperature by changing the confinement aspect ratio and/or dipole moment strength. We find that the entropy of a trapped dipolar crystal can be much larger than the entropy in the liquid state at zero dipole moment, indicating a polarization cooling mechanism during the formation of dipolar crystal when the external field is increased adiabatically. Our results therefore have significant application to the experimental preparation of a self-assembled dipolar crystal using ultracold polar molecules.