NMR evidence of strong-correlated superconductivity in LiFeAs: tuning toward an SDW ordering

TL;DR

This study uses NMR to investigate LiFeAs, revealing strong spin fluctuations and tunability toward SDW order, indicating that superconductivity arises from these correlated magnetic fluctuations.

Contribution

It provides evidence that LiFeAs is a strongly correlated system where superconductivity is linked to SDW fluctuations and demonstrates how sample conditions influence magnetic ordering.

Findings

Strong low-temperature spin fluctuations detected

Sample tuning can induce SDW quantum-critical point

Off-stoichiometry may suppress SDW order

Abstract

In this letter, we reported the results of NMR study on LiFeAs single crystals. We find a strong evidence of the low temperature spin fluctuations; by changing sample preparation conditions, the system can be tuned toward an spin-density-wave (SDW) quantum-critical point. The detection of an interstitial Li(2) ion, possibly locating in the tetrahedral hole, suggests that the off-stoichiometry and/or lattice defect can probably account for the absence of the SDW ordering in LiFeAs. These facts show that LiFeAs is a strongly correlated system and the superconductivity is likely originated from the SDW fluctuations.