Dual bands of negative refraction with low absorption in a quasi-Λ four-level left-handed atomic system

Dual bands of left-handedness are obtained in a quasi-K four-level atomic system. In our system, multichannel quantum interference plays a very important role on the realization of dual bands. It is shown that the permeability can realize negative values in dual bands of this four-level atomic system. Moreover, the permittivity and permeability can simultaneously realize negative values in the same frequency band. It can be found that the atomic system exhibits negative refraction with low absorption in each left-handed frequency band. At some certain frequencies, this left-handed atomic system can obtain zero absorption.