Parity violation in metals

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Abstract
In this paper we study parity violation in metals, induced by the electroweak interaction of the conduction electrons with the nuclei of the lattice. The effects discussed here involve the same electroweak parameter — the weak charge Qw — as in atomic parity violation and the variation with the atomic number also obeys a Z3 law. The mechanisms which provide the enhancement necessary to bring the left-right asymmetry to the level of 10-5-10 -6 are however very different from the ones which are operating in atomic experiments. They can be viewed as long-range cooperative phenomena associated with the delocalization of the conduction electrons. The p.v. effects, not involving interband transitions, only appear when the metal is perturbed by an inhomogeneous magnetic field. An interesting example is the modification of the RKKY interaction between magnetic impurities. The actual observation of this effect, which is one of the very few cases of static manifestation of parity violation, appears unfortunately as a very difficult enterprise. More favourable experimental conditions could be achieved in magnetic electron spin resonance. The oscillating magnetization transmitted through a metallic slab is subjected to small rotation around the normal to the slab of about one milliradian per centimeter. Under these circumstances where the Landau levels are well separated, the spin resonance transition probability exhibits a left-right asymmetry of the order of 2 x 10-6 cotg θ, where θ is the angle between the a.c. and d.c. magnetic fields. Although our analysis is of general character, all the numerical estimates have been performed for the case of metallic caesium