Observation of anomalous Hanle spin precession lineshapes resulting from interaction with localized states

TL;DR

This paper demonstrates that localized states can alter Hanle spin precession lineshapes in graphene, revealing new insights into spin interactions that are not accessible through charge transport measurements.

Contribution

It shows that localized states can modify Hanle curves, providing a new method to analyze spin interactions in materials with localized states.

Findings

Localized states change Hanle lineshapes at low temperatures.

The effect varies with different growth methods.

Analysis yields localized state density and coupling information.

Abstract

It has been shown recently that in spin precession experiments, the interaction of spins with localized states can change the response to a magnetic field, leading to a modified, effective spin relaxation time and precession frequency. Here, we show that also the shape of the Hanle curve can change, so that it cannot be fitted with the solutions of the conventional Bloch equation. We present experimental data that shows such an effect arising at low temperatures in epitaxial graphene on silicon carbide with localized states in the carbon buffer layer. We compare the strength of the effect between materials with different growth methods, epitaxial growth by sublimation and by chemical vapor deposition. The presented analysis gives information about the density of localized states and their coupling to the graphene states, which is inaccessible by charge transport measurements and can be applied to any spin transport channel that is coupled to localized states.