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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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