Signatures of unconventional pairing in spin-imbalanced one-dimensional few-fermion systems

Daniel Pęcak,Tomasz Sowiński

doi:10.1103/physrevresearch.2.012077

Daniel Pęcak, Tomasz Sowiński

Open Access

https://doi.org/10.1103/physrevresearch.2.012077

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Abstract

A system of a few attractively interacting fermionic $^6$Li atoms in one-dimensional harmonic confinement is investigated. Non-trivial inter-particle correlations induced by interactions in a particle-imbalanced system are studied in the framework of the noise correlation. In this way, it is shown that evident signatures of strongly correlated fermionic pairs in the Fulde-Ferrell-Larkin-Ovchinnikov state are present in the system and they can be detected by measurements directly accessible within state-of-the-art techniques. The results convincingly show that the exotic pairing mechanism is a very universal phenomenon and can be captured in systems being essentially non-uniform and far from the many-body limit.

Highlights

One of the cornerstones of our understanding of strongly correlated states of quantum matter is based on the theory of superconductivity by Bardeen, Cooper, and Schrieffer [1]
It is shown that evident signatures of strongly correlated fermionic pairs in the Fulde-Ferrell-Larkin-Ovchinnikov state are present in the system and they can be detected by measurements directly accessible within state-of-the-art techniques
The results convincingly show that the exotic pairing mechanism is a very universal phenomenon and can be captured in systems being essentially nonuniform and far from the many-body limit

Summary

Introduction

One of the cornerstones of our understanding of strongly correlated states of quantum matter is based on the theory of superconductivity by Bardeen, Cooper, and Schrieffer [1]. One of the most influential extensions of the Cooper’s idea comes from the observation that in the case of imbalanced systems, due to the mismatch of Fermi spheres of different components, the formation of correlated pairs forced by attractive mutual interactions is inseparably connected with a resulting nonzero net momentum of the pair [6,7] This unconventional pairing mechanism named after Fulde, Ferrell, Larkin, and Ovchinnikov (FFLO) has been extensively examined theoretically, mostly in the case of various solid-state systems such as iron-based superconductors [8,9,10,11,12], heavy-fermion compounds [11,13,14,15,16], or organic conductors [17,18,19]. Alternative theoretical approaches are proposed to capture the correlations, including the usage of bosons [26], and dynamical processes [27]

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