High Sensitivity RF Spectroscopy of a Strongly-Interacting Fermi Gas

TL;DR

This paper introduces a highly sensitive rf spectroscopy method for ultracold fermionic gases, enabling detection of weak signals, extending energy measurement range, and verifying universal fermion properties with precise Feshbach molecule binding energy measurements.

Contribution

The study presents a novel rf spectroscopy scheme that detects extremely weak signals and extends the energy measurement range, allowing direct verification of universal fermion properties and precise Feshbach resonance calibration.

Findings

Detected signals of only a few atoms.

Extended photon-energy range by an order of magnitude.

Verified power-law scaling of rf spectrum tail.

Abstract

Rf spectroscopy is one of the most powerful probing techniques in the field of ultracold gases. We report on a novel rf spectroscopy scheme with which we can detect very weak signals of only a few atoms. Using this method, we extended the experimentally accessible photon-energies range by an order of magnitude compared to previous studies. We verify directly a universal property of fermions with short-range interactions which is a power-law scaling of the rf spectrum tail all the way up to the interaction scale. We also employ our technique to precisely measure the binding energy of Feshbach molecules in an extended range of magnetic fields. This data is used to extract a new calibration of the Feshbach resonance between the two lowest energy levels of 40K