  2-D(Two-dimensional) isotropic negative refractive index (NRI) is explicitly
realized via the orthogonal signal and coupling standing-wave fields coupling
the N-type four-level atomic system. Under some key parameters of the dense
vapor media, the atomic system exhibits isotropic NRI with simultaneous
negative permittivity and permeability (i.e. Left-handedness) in the 2-D x-y
plane. Compared with other 2-D NRI schemes, the coherent atomic vapor media in
our scheme may be an ideal 2-D isotropic NRI candidate and has some potential
advantages, significance or applications in the further investigation.
