Observation of Roton Mode Population in a Dipolar Quantum Gas

Understand

The concept of a roton, a special kind of elementary excitation, forming a minimum of energy at finite momentum, has been essential to understand the properties of superfluid $^4$He.

• In quantum liquids, rotons arise from the strong interparticle interactions, whose microscopic description remains debated.
• In the realm of highly-controllable quantum gases, a roton mode has been predicted to emerge due to magnetic dipole-dipole interactions despite of their weakly-interacting character.
• This prospect has raised considerable interest; yet roton modes in dipolar quantum gases have remained elusive to observations.