Materials with a negative index of refraction are substances in which either one or both of the permittivity and the permeability of the medium is negative. Whereas the permittivity of the medium is well defined and related to the frequency-dependent polarizability, the dispersion behaviour of the permeability is not as well defined. The relation between the macroscopic permeability and the microscopic quantity describing the interaction with the magnetic component of the electromagnetic field, the frequency-dependent magnetizability, is in contrast poorly understood. Indeed, even the definition of the frequency-dependent magnetizability appear unsatisfactory.
A theory for the frequency-dependent magnetizability has been presented by Raab and de Lange [1], and these authors have also considered the frequency-dependent permeability [2]. However, the expression derived for the frequency-dependent magnetizability is based on a number of assumptions, making the theory somewhat unsatisfactory.
In this talk, we will discuss our recent analysis of the frequency-dependent magnetizability, and propose a new way of deriving the frequency-dependent permittivity, inverse permeability and magnetizability starting from an analysis of the current-current response function.
[1] R.E.Raab and O.L.de Lange. * Mol.Phys.* ** 104**, 1925 (2006).
[2] R.E.Raab and O.L.de Lange. * Proc.~Royal Soc.* ** 461**, 595 (2005). |