Quantum-mechanical water-flow enhancement through a sub-nanometer carbon nanotube

Experimental observations unambiguously reveal quasi-frictionless water flow through nanometer-scale carbon nanotubes (CNTs). Classical fluid mechanics is deemed unfit to describe this enhanced flow, and recent investigations indicated that quantum mechanics is required to interpret the extremely weak water-CNT friction. In fact, by quantum scattering, water can only release discrete energy upon excitation of electronic and phononic modes in the CNT. Here, we analyze in detail how a traveling water molecule couples to both plasmon and phonon excitations within a sub-nanometer, periodic CNT. We find that the water molecule needs to exceed a minimum speed threshold of similar to 50 m/s in order to scatter against CNT electronic and vibrational modes. Below this threshold, scattering is suppressed, as in standard superfluidity mechanisms. The scattering rates, relevant for faster water molecules, are also estimated.

Automated summary

Experimental observations show the existence of quasi-frictionless water flow through nanometer-scale carbon nanotubes. Quantum mechanics is necessary to explain this phenomenon. This study analyzes the coupling between water molecules and plasmon and phonon excitations in carbon nanotubes, and finds that a certain speed threshold is required for scattering against the electronic and vibrational modes.