6533b7defe1ef96bd127656f

RESEARCH PRODUCT

Low-energy excitations from interacting tunneling units in the mean-field approximation

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Abstract The low-energy excitation spectrum of dilute concentrations of interacting tunneling quadrupoles randomly distributed in a non-polar medium was studied in the mean-field approximation. In particular the case of six-orientational tunneling quadrupoles (TQs) with a r−3 (elastic) interaction was considered. Because of the random position of the TQs, the internal field in a random variable and for relatively low concentrations has a Lorenzian probability distribution. The low-energy density of states is a constant and the low-energy excitations arise from the large internal fields, i.e. strongly interacting tunneling quadrupoles. The low-energy excitations were compared with those obtained from a virial expansion of the free energy for very dilute concentrations of interacting TQs. Contrary to the standard tunneling model for glasses, in both cases the low-energy excitations were found to arise from the strongly interacting tunneling quadrupoles.