Theory of motional inhibition of interlayer quantum tunneling in thin 3He films

Publication Date


Journal or Book Title

Journal of Low Temperature Physics


An attempt is made to interpret NMR data on 3He films for coverages just over one monolayer in terms of motion due to the quantum exchange of particles between layers. A summary of the relevant data and of various possible relaxation mechanisms is given and it is found that a portion of the data seems amenable to an interlayer exchange interpretation. The detailed theory of this process requires the use of the exchange operator concept and a Kubo-theory treatment of the effect of second-layer motion on the exchange process. It is shown that the ldquobarerdquo interlayer exchange process characterized by constant J 12 is slowed by second-layer translational motion so that the effective exchange parameter becomes \~J 12 ap J 12 2/epsiv2, where epsiv2 is a second-layer single-particle translational energy. In order to fit the NMR data it is found that epsiv2 must be evaluated in the classical limit rather than the degenerate Fermi limit, and that \~J 12 ap J 11, the exchange energy within the first-layer solid. These conditions require a helium second-layer effective mass of m * > 5m and J 12>600J 11, which are anomously large values for these