Supermassive black hole binaries ( SMBHBs ) are products of galaxy mergers , and are important in testing \Lambda cold dark matter cosmology and locating gravitational-wave-radiation sources .
A unique electromagnetic signature of SMBHBs in galactic nuclei is essential in identifying the binaries in observations from the IR band through optical to X-ray .
Recently , the flares in optical , UV , and X-ray caused by supermassive black holes ( SMBHs ) tidally disrupting nearby stars have been successfully used to observationally probe single SMBHs in normal galaxies .
In this Letter , we investigate the accretion of the gaseous debris of a tidally disrupted star by a SMBHB .
Using both stability analysis of three-body systems and numerical scattering experiments , we show that the accretion of stellar debris gas , which initially decays with time \propto t ^ { -5 / 3 } , would stop at a time T _ { tr } \simeq \eta T _ { b } .
Here , \eta \sim 0.25 and T _ { b } is the orbital period of the SMBHB .
After a period of interruption , the accretion recurs discretely at time T _ { r } \simeq \xi T _ { b } , where \xi \sim 1 .
Both \eta and \xi sensitively depend on the orbital parameters of the tidally disrupted star at the tidal radius and the orbit eccentricity of SMBHB .
The interrupted accretion of the stellar debris gas gives rise to an interrupted tidal flare , which could be used to identify SMBHBs in non-active galaxies in the upcoming transient surveys .