# Negative group velocity and Kelvin-like wake in superfluid $^{4}He$

@inproceedings{Kolomeisky2021NegativeGV, title={Negative group velocity and Kelvin-like wake in superfluid \$^\{4\}He\$}, author={E. B. Kolomeisky and Jonathan Colen and J. Straley}, year={2021} }

The dispersion law Ω(k) of elementary excitations in superfluid He is a non-monotonic function of the wave number k. After an initial increase, the function Ω(k) reaches a maximum followed by a ”roton” minimum at finite k. As a result, there is a range of k between these extrema where the elementary excitations have negative group velocity. These excitations are generated when a fast heavy impurity travels through the superfluid or the latter flows past an obstacle with the speed exceeding 60 m… Expand

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