Nuclear spin-lattice relaxation in superlattices

The nuclear spin-lattice relaxation rate in a superlattice subjected to a strong magnetic field H parallel to its axis is studied theoretically. The energy conservation law allows flip-flop spin-reversal processes due to the hyperfine interaction between the nuclear and electron spins only in some intervals of H. In particular, the width of the highest occupied superlattice subband /spl Delta/ must exceed the spin splitting of Landau levels, which results in the relaxation offset at some critical magnetic field H/sub 2/. At H