| Popis: |
Superfluidity is a well-characterized quantum phenomenon which entails frictionless-motion of mesoscopic particles through a superfluid, such as $^4$He or dilute atomic-gases at very low temperatures. As shown by Landau, the incompatibility between energy- and momentum-conservation, which ultimately stems from the spectrum of the elementary excitations of the superfluid, forbids quantum-scattering between the superfluid and the moving mesoscopic particle, below a critical speed-threshold. Here we predict that frictionless-motion can also occur in the absence of a standard superfluid, i.e. when a He atom travels through a narrow (5,5) carbon-nanotube (CNT). Due to the quasi-linear dispersion of the plasmon and phonon modes that could interact with He, the (5,5) CNT embodies a solid-state analog of the superfluid, thereby enabling straightforward transfer of Landau's criterion of superfluidity. As a result, Landau's equations acquire broader generality, and may be applicable to other nanoscale friction phenomena, whose description has been so far purely classical. |
