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Breaking the roton barrier: an experimental study of motion faster than the Landau critical velocity for roton creation in He II.

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<mark>Journal publication date</mark>16/12/1974
<mark>Journal</mark>Physical review letters
Issue number25
Number of pages4
Pages (from-to)1468-1471
Publication StatusPublished
<mark>Original language</mark>English


We report the first observation of objects moving through He II with equilibrium drift velocities v beyond the Landau critical velocity vc,for roton creation. With T about 0.4 K, P = 25 bar, F =2 kV/cm, (v - vc) for negative ions is larger than a theoretical prediction by a factor of about 10^5. The vortex-ring nucleation rate is found to decrease with F above 300 V/cm, thus resolving apparent inconsistencies between earlier experiments.