Abstract
Title: "Relativistic analysis of magnetoelectric crystals: extracting a new 4-dimensional P odd and T odd pseudoscalar from Cr_2 O_3 data"
Abstract:
Earlier, the magnetoelectric effect of chromium sesquioxide
Cr_2 O_3 has been determined experimentally as a function of
temperature. One put Cr_2 O_3 crystals in a static electric field
and measured its magnetization or put it in a static magnetic field
and measured its electric polarization. From the magnetoelectric
moduli of Cr_2 O_3 we extract a 4-dimensional relativistic
invariant pseudoscalar tilde{alpha}. It is temperature dependent
and of the order of ~ 10^{-4}/Omega_0, with Omega_0 as
vacuum impedance. We show that the new pseudoscalar is odd under
parity transformation and odd under time inversion. Moreover,
tilde{alpha} is for Cr_2 O_3 what Tellegen's {\it gyrator} is
for two port theory, the {\it axion} field for axion electrodynamics,
and the PEMC (perfect electromagnetic conductor) for electrical
engineering.