Simultaneous negative permittivity and permeability in a coherent atomic vapour

A new quantum optical mechanism to realize simultaneously negativeelectric permittivity and magnetic permeability is suggested. Inorder to obtain a negative permeability, we choose a proper atomicconfiguration that can dramatically enhance the contribution of themagnetic-dipole allowed transition via the atomic phase coherence. Itis shown that the atomic system chosen with proper optical parameterscan give rise to striking electromagnetic responses (leading to anegative refractive index) and that the atomic vapour becomes aleft-handed medium in an optical frequency band. Differing from theprevious schemes of artificial composite metamaterials (based onclassical electromagnetic theory) to achieve the left-handedmaterials, which consist of anisotropic millimetre-scale compositestructure units, the left-handed atomic vapour presented here isisotropic and homogeneous at the atomic-scale level. Such anadvantage may be valuable in realizing the superlens (and henceperfect image) with left-handed atomic vapour.