Violation of Fundamental Symmetries in Solid State Physics
 
There have been several very interesting developments in 2001, but the most exciting, in my opinion, is the one related to studies of CP-violation in solid state physics.

Violation of the combined symmetry of charge conjugation (C) and parity (P) was discovered in the decay of the K0 meson about 40 years ago. The exact origin of this symmetry violation remains an enigma, although the so called standard model of electroweak interactions can describe these processes phenomenologically. It has been also proposed by Sakharov that the matter-antimatter asymmetry observed in our Universe could have arisen from a CP-violating interaction active at an early stage of the Big Bang. The CP-violation implies a time-reversal (T) asymmetry and hence violation of the combined TP-symmetry, because there are strong reasons to believe that the combined CPT-symmetry should not be violated. An electric dipole moment (EDM) of a system in a stationary quantum state indicates violation of the TP-symmetry; this is why searches of EDM of elementary particles, atoms and molecules is a very important direction for studies of violations of fundamental symmetries. We concentrate on the EDM of the electron de.

The present best limitation on de comes from the Berkeley experiment with an atomic Thallium beam, which gives de < 1.6x 10-27 e cm. There are some ideas for improvement of the sensitivity. The most promising “conventional” way of improvement is an experiment with metastable levels of the PbO molecule. However a real breakthrough can be achieved in solid state experiments. This is a recent suggestion of two experimental groups: S.K. Lamoreaux (Los Alamos) and L. R. Hunter (Amherst). According to their estimates based on our preliminary theoretical analysis, improvement of the present sensitivity of up to six orders of magnitude is feasible in experiments with the compounds Gadolinium Iron Garnet and Gadolinium Gallium Garnet. This improvement is based on a) High density of Gd3+ ions in the compounds, b) A novel way to detect magnetization, c) A relatively high EDM enhancement in the Gd3+ ion.

We will continue studies of the problem. If initial theoretical and experimental estimates are confirmed this direction will provide a real breakthrough in studies of fundamantal symmetries.

Oleg Sushkov

 
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