  We analyze different factors which influence the negative refraction in
solids and multi-atom molecules. We find that this negative refraction is
significantly influenced by simultaneous multi-electron transitions with the
same transition frequency and dipole redistribution over different eigenstates.
We show that these simultaneous multi-electron transitions and enhanced
transition dipole broaden the bandwidth of the negative refraction by at least
one order of magnitude. This work provides additional connection between
metamaterials and Mobius strips.
