Structure of metastable 2D liquid heliumV. Apaja1 and M. Saarela2
1 Department of Physics, University of Jyväskylä - P.O. Box 35, FIN-40014, Finland, EU
2 Department of Physical Sciences, University of Oulu - P.O. Box 3000, FIN-90014, Finland, EU
received 15 July 2008; accepted in final form 3 October 2008; published November 2008
published online 30 October 2008
We present diffusion Monte Carlo (DMC) results on a novel, superfluid phase in two-dimensional 4He at densities higher than 0.065 Å-2, which is very close to the freezing density. The new phase has anisotropic, hexatic orbital order, but the single-particle density remains constant. By increasing density the hexatic superfluid forms a metastable state, which lies above the crystal ground state in energy. This implies that the liquid-solid phase transition takes place in two stages: a second-order phase transition from the isotropic superfluid to the hexatic superfluid, followed by a first-order transition that localizes atoms into the triangular crystal order.
02.70.Ss - Quantum Monte Carlo methods.
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