Influence of quadrupolar interaction on NMR spectroscopy

TL;DR

This paper investigates how nuclear quadrupolar interactions affect NMR spectroscopy signals in quantum dots, finding that these interactions do not explain the absence of expected spectral dips in experiments.

Contribution

The study demonstrates through simulations that quadrupolar interactions do not cause the disappearance of characteristic dips in NMR signals, challenging previous assumptions.

Findings

Quadrupolar interactions do not alter the width or relative depth of spectral dips.

The absolute depth of dips decreases with quadrupolar interactions.

Quadrupolar interactions alone cannot explain experimental discrepancies.

Abstract

Optically driven electronic spins coupled in quantum dots to nuclear spins show a pre-pulse signal (revival amplitude) after having been trained by long periodic sequences of pulses. The size of this revival amplitude depends on the external magnetic field in a specific way due to the varying commensurability of the nuclear Larmor precession period with the time $T_\text{rep}$ between two consecutive pulses. In theoretical simulations, sharp dips occur at fields when an integer number of precessions fits in $T_\text{rep}$; this feature could be used to identify nuclear isotopes spectroscopically. But these sharp and characteristic dips have not (yet) been detected in experiment. We study whether the nuclear quadrupolar interaction is the reason for this discrepancy because it perturbs the nuclear precessions. But our simulations show that the absolute width of the dips and their relative depth are not changed by quadrupolar interactions. Only the absolute depth decreases. We conclude that quadrupolar interaction alone cannot be the reason for the absence of the characteristic dips in experiment.