A Single Scalar Field Model of Dark Energy with Equation of State   Crossing -1
  In this paper we study the possibility of building models of dark energy with equation of state across -1 and propose explicitly a model with a single scalar field which gives rise to an equation of state larger than -1 in the past and less than -1 at the present time, consistent with the current observations. 
Mingzhe Li, Bo Feng, and Xinmin Zhang