Observation of p-wave Threshold Law Using Evaporatively Cooled Fermionic Atoms

TL;DR

This study measures s-wave and p-wave collision rates in ultracold fermionic potassium-40 atoms, confirming the p-wave threshold law and its suppression effects, and reports initial cooling results toward quantum degeneracy.

Contribution

It provides the first direct observation of the p-wave threshold law in ultracold fermionic atoms and details the collision dynamics relevant for quantum degeneracy.

Findings

Large positive s-wave scattering length identified

Direct observation of p-wave threshold law confirmed

Initial evaporative cooling results achieved

Abstract

We have measured independently both s-wave and p-wave cross-dimensional thermalization rates for ultracold potassium-40 atoms held in a magnetic trap. These measurements reveal that this fermionic isotope has a large positive s-wave triplet scattering length in addition to a low temperature p-wave shape resonance. We have observed directly the p-wave threshold law which, combined with the Fermi statistics, dramatically suppresses elastic collision rates at low temperatures. In addition, we present initial evaporative cooling results that make possible these collision measurements and are a precursor to achieving quantum degeneracy in this neutral, low-density Fermi system.