Adjusting the left-handedness in a cold 87Rb atomic system via multiple parameter modulation

We demonstrate adjusting the left-handedness in a cold 87Rb atomic system by its number density, the strong coupling field and two incoherent pumping fields. The results show that a higher density of 87Rb atoms and a stronger coupling field can influence the left-handedness more, while increasing the two incoherent pumping fields enhances the negative magnetic response but depresses the negative electric response. The left-handedness adjusted by multiple parameter in a cold 87Rb atomic system provides the flexibility and feasibility for the coming experiments.