Crossing $w=-1$ by a single scalar field coupling with matter and the
  observational constraints
  Motivated by Yang-Mills dark energy model, we propose a new model by
introducing a logarithmic correction. we find that this model can avoid the
coincidence problem naturally and gives an equation of state $w$ smoothly
crossing -1 if an interaction between dark energy and dark matter exists. It
has a stable tracker solution as well. To confront with observations based on
the combined data of SNIa, BAO, CMB and Hubble parameter, we obtain the best
fit values of the parameters with $1\sigma, 2\sigma, 3\sigma$ errors for the
noncoupled model: $\Omega_m=0.276\pm0.008^{+0.016+0.024}_{-0.015-0.022}$,
$h=0.699\pm0.003\pm0.006\pm0.008$, and for the coupled model with a decaying
rate $\gamma=0.2$: $\Omega_m=0.291\pm0.004^{+0.008+0.012}_{-0.007-0.011}$,
$h=0.701\pm0.002\pm0.005\pm0.007$. In particular, it is found that the
non-coupled model has a dynamic evolution almost undistinguishable to
$\Lambda$CDM at the late-time Universe.
