An adapted strong coupling calculation in disordered solids yielding acoustic bistability

We consider single well anharmonic oscillator like defects coupled to a perfect elastic medium, the coupling term being bilinear in the strain field and in the defect variables. The elastostatic self-interaction energy of the defects is negative and can turn efficiently the single well into a double well, giving a natural explanation for the existence of two level systems in glasses. (C) 1997 Elsevier Science B.V.