Dynamic melting of driven vortex matter below 1Â K

We report on measurements of a mode-locking resonance in amorphous MoxGe1−x films at different temperatures T down to 0.8 K, which is well below the superconducting transition (6 K). We observe dynamic ordering of driven vortex matter for all the temperatures studied. As the field exceeds a certain critical field Bc,dyn at fixed T, moving vortices do not exhibit dynamic ordering. At high T, this field Bc,dyn(T), so-called dynamic melting, nearly coincides with a characteristic field Bc(T) where the linear resistivity vanishes. At low T, however, Bc,dyn(T) is significantly suppressed compared to Bc(T), suggesting intrinsic quantum melting in the absence of pinning.