In this paper we put forward a running coupling scenario for describing the interaction between dark energy and dark matter .
The dark sector interaction in our scenario is free of the assumption that the interaction term Q is proportional to the Hubble expansion rate and the energy densities of dark sectors .
We only use a time-variable coupling b ( a ) ( with a the scale factor of the universe ) to characterize the interaction Q .
We propose a parametrization form for the running coupling b ( a ) = b _ { 0 } a + b _ { e } ( 1 - a ) in which the early-time coupling is given by a constant b _ { e } , while today the coupling is given by another constant , b _ { 0 } .
For investigating the feature of the running coupling , we employ three dark energy models , namely , the cosmological constant model ( w = -1 ) , the constant w model ( w = w _ { 0 } ) , and the time-dependent w model ( w ( a ) = w _ { 0 } + w _ { 1 } ( 1 - a ) ) .
We constrain the models with the current observational data , including the type Ia supernova , the baryon acoustic oscillation , the cosmic microwave background , the Hubble expansion rate , and the X-ray gas mass fraction data .
The fitting results indicate that a time-varying vacuum scenario is favored , in which the coupling b ( z ) crosses the noninteracting line ( b = 0 ) during the cosmological evolution and the sign changes from negative to positive .
The crossing of the noninteracting line happens at around z = 0.2 - 0.3 , and the crossing behavior is favored at about 1 \sigma confidence level .
Our work implies that we should pay more attention to the time-varying vacuum model and seriously consider the phenomenological construction of a sign-changeable or oscillatory interaction between dark sectors .