$\beta$-Detected NMR of $^8$Li in the Normal State of 2H-NbSe$_2$

TL;DR

This study uses $eta$-NMR to investigate $^8$Li in the normal state of 2H-NbSe$_2$, revealing insights into its local environment, magnetic properties, and lithium positioning within the crystal structure.

Contribution

It provides the first $eta$-NMR measurements of $^8$Li in 2H-NbSe$_2$, showing weak electric field gradients and Korringa relaxation, indicating interstitial lithium placement.

Findings

Single resonance observed with 3.5 kHz Gaussian line width

Line shape weakly varies with magnetic field and temperature, strongly depends on orientation

Nuclear spin relaxation rate is small and linearly temperature-dependent

Abstract

$\beta$-NMR of isolated $^8$Li has been investigated in the normal state of 2H-NbSe$_2$. In a high magnetic field of 3T a single resonance is observed with a Gaussian line width of 3.5 kHz. The line shape varies weakly as function of magnetic field and temperature but has a strong orientation dependence. The nuclear electric quadrupole splitting is unresolved implying that the electric field gradients are 10-100 times smaller than in other non-cubic crystals. The nuclear spin relaxation rate is also anomalously small but varies linearly with temperature as expected for Korringa relaxation in a metal. These results suggest that Li adopts an interstitial position between the weakly coupled NbSe$_2$ layers and away from the conduction band.