Resistively-Detected NMR in a Two-Dimensional Electron System near $\nu = 1$: Clues to the Origin of the Dispersive Lineshape

TL;DR

This study investigates resistively-detected NMR in a 2D electron system near the $ u=1$ quantum Hall state, revealing a persistent dispersive lineshape and Korringa relaxation, with implications for understanding the underlying physics.

Contribution

It reports the first observation of a consistent dispersive lineshape and Korringa relaxation in this regime, challenging previous findings and suggesting combined Zeeman and thermal effects.

Findings

Dispersive lineshape observed at all RF powers

Korringa-like nuclear spin-lattice relaxation detected

Lineshape inverts with sign change in temperature derivative of resistance

Abstract

Resistively-detected NMR measurements on 2D electron systems near the $\nu = 1$ quantum Hall state are reported. In contrast to recent results of Gervais \emph{et al.} [Phys. Rev. Lett. $\bf 94$, 196803 (2005)], a dispersive lineshape is found at all RF powers studied and Korringa-like nuclear spin-lattice relaxation is observed. The shape of the unexplained dispersive lineshape is found to invert when the temperature derivative of the longitudinal resistance changes sign. This suggests that both Zeeman and thermal effects are important to resistively-detected NMR in this regime.