Experimental Observation of a Self-Heating Effect of Helium-4 Superflow

Abstract: We report a counter-intuitive self-heating effect of helium-4 superflow. This fundamentally unusual heating effect bears a phenomenological resemblance to the Peltier effect of electric current across two different conductors. It reveals that helium-4 superflow carries thermal energy and entropy, which is in contrast to the two-fluid model of superfluid helium-4. A natural understanding of this heating effect is provided by a recently developed microscopic quantum theory of superfluid helium-4.