Adjusting the left-handedness in a cold ${}^{87}$Rb atom via multiple parameter modulation

We demonstrate the adjusting left-handedness in the cold ${}^{87}$Rb atom by its number density, the strong coupling field and two incoherent pumping fields. The results show that more dense ${}^{87}$Rb atoms and more stronger coupling field can influence the left-handedness more greatly, while the increasing two incoherent pumping fields construct the negative magnetic response but depress the negative electric response. The left-handedness adjusted by multiple parameter in the cold ${}^{87}$Rb atomic system provides the flexibility and feasibility for the coming experiment.