The FFLO state in the one-dimensional attractive Hubbard model and its fingerprint in the spatial noise correlations

TL;DR

This paper investigates the FFLO state in a one-dimensional attractive Hubbard model with spin imbalance, demonstrating its dominance and stability through theoretical analysis and DMRG simulations, and suggesting experimental detection methods.

Contribution

It provides a detailed analysis of the FFLO phase in 1D Hubbard models, including correlation exponents and noise correlation signatures, with new insights into its stability and experimental observability.

Findings

FFLO pairing is always dominant in spin-imbalanced 1D systems.

No Chandrasekhar-Clogston limit exists for the FFLO phase.

Spatial noise correlations reveal nonzero momentum fermion pairs.

Abstract

We explore the pairing properties of the one-dimensional attractive Hubbard model in the presence of finite spin polarization. The correlation exponents for the most important fluctuations are determined as a function of the density and the polarization. We find that in a system with spin population imbalance, Fulde-Ferrell-Larkin-Ovchinnikov (FFLO)-type pairing at wavevector Q=|k_{F,\uparrow}-k_{F,\downarrow}| is always dominant and there is no Chandrasekhar-Clogston limit. We then investigate the case of weakly coupled 1D systems and determine the region of stability of the 1D FFLO phase. This picture is corroborated by density-matrix-renormalization-group (DMRG) simulations of the spatial noise correlations in uniform and trapped systems, unambiguously revealing the presence of fermion pairs with nonzero momentum Q. This opens up an interesting possibility for experimental studies of FFLO states.