Novel Composite Medium Exhibits Reversed Electromagnetic Properties

According to Maxwell's equations, lossless propagation of electromagnetic waves requires the index of refraction n, given by $(εμ)1/2,$ to be real, where ε is the electrical permittivity or dielectric constant and μ is the magnetic permeability. All familiar materials have a positive μ and, for the most part, positive ε. But at the March Meeting of the American Physical Society, held in Minneapolis, a group of researchers from the University of California, San Diego, led by David Smith and Sheldon Schultz, reported having built a composite medium with an effective μ that is negative. By combining that medium with one that has a negative ε, they have created a composite material that allows transmission of microwaves that would be blocked by either medium alone. But the propagation inside the composite is predicted to have unusual properties, such as a negative index of refraction.