Extraordinary behavior of4He on hydrogen and deuterium surfaces

Using third sound resonance below 1 K, for⁴He on solid H₂ and D₂ surfaces, we have found new phenomena. On H₂ we find surface superfluidity for⁴He coverages less than one layer, with the zero temperature Kosterlitz-Thouless (KT) transition extrapolated to a coverage of 0.35±0.05 layers. On both H₂ and D₂ we find a new line of transitions below the KT transitions. On H₂, at zero temperature, the new line of transitions starts at zero temperature at a coverage of 0.6±0.1 layers of⁴He and has a slope of 0.58 (K/layer) of the universal KT slope. We also find, on H₂, two modes of surface wave propagation between the new transition and the KT transition. Below the new transition we also find anomalous third sound absorption which increases exponentially with temperature by five orders of magnitude.