Oscillons and propagating solitary waves in a vertically vibrated colloidal suspension

The observation of localized stationary structures, coined oscillons, in gr anular media has evoked much interest. By parametric excitation of clay sus pensions, we demonstrate a hysteretic transition to oscillon-type states in a nongranular medium. When the symmetry of up-down reflection + time trans lation is lost, these states undergo a transition to propagating localized states previously seen in Newtonian fluids. These observations are in accor d with recent theoretical predictions of sufficient conditions for oscillon formation. In addition, a novel measurement technique fur the effective su spension viscosity demonstrates their sheer-thinning properties.