Single Impurity In Ultracold Fermi Superfluids

TL;DR

This paper investigates how a single magnetic impurity affects ultracold Fermi superfluids, revealing it can induce mid-gap states and an FFLO phase, and proposes a spectroscopic detection method.

Contribution

It demonstrates that a magnetic impurity can controllably induce an FFLO state in ultracold Fermi superfluids under current experimental conditions.

Findings

Magnetic impurities induce mid-gap bound states.

Impurities can trigger FFLO phases.

Proposed RF spectroscopy for detection.

Abstract

The role of impurities as experimental probes in the detection of quantum material properties is well appreciated. Here we study the effect of a single classical magnetic impurity in trapped ultracold Fermi superfluids. Depending on its shape and strength, a magnetic impurity can induce single or multiple mid-gap bound states in a superfluid Fermi gas. The multiple mid-gap states could coincide with the development of a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase within the superfluid. As an analog of the Scanning Tunneling Microscope, we propose a modified RF spectroscopic method to measure the local density of states which can be employed to detect these states and other quantum phases of cold atoms. A key result of our self consistent Bogoliubov-de Gennes calculations is that a magnetic impurity can controllably induce an FFLO state at currently accessible experimental parameters.