Increasing Quantum Degeneracy by Heating a Superfluid

TL;DR

This paper demonstrates a novel thermomechanical effect in superfluids where heating one compartment causes atoms to flow from hot to cold, increasing quantum degeneracy in the colder region, applicable to superfluid helium and dilute gases.

Contribution

It introduces a new thermomechanical effect where heating induces atom flow from hot to cold, increasing degeneracy, differing from the fountain effect in superfluid helium.

Findings

Atoms flow from hot to cold under certain conditions.

Quantum degeneracy increases in the colder compartment.

Effect occurs at all temperatures below Tc in dilute gases.

Abstract

We consider a uniform superfluid confined in two compartments connected by a superleak and initially held at equal temperatures. If one of the two compartments is heated, a fraction of the superfluid will flow through the superleak. We show that, under certain thermodynamic conditions, the atoms flow from the hotter to the colder compartment, contrary to what happens in the fountain effect observed in superfluid Helium. This flow causes quantum degeneracy to increase in the colder compartment. In superfluid Helium, this novel thermomechanical effect takes place in the phonon regime of very low temperatures. In dilute quantum gases, it occurs at all temperatures below Tc . The increase in quantum degeneracy reachable through the adiabatic displacement of the wall separating the two compartments is also discussed.