Resistively detected-NMR in triple-gate quantum point contact: magnetic field dependence

Here we show RD-NMR signal dependency on magnetic field in a GaAs based quantum point contact (QPC) in quantum Hall breakdown regime. For this purposes we employ triple gate QPC to control the confinement of 2DEG and locally generate nuclear spin polarization. We focused on the detection of 75As RD-NMR signal at different perpendicular magnetic field in the presence of electrons occupying the lowest Landau level. We manage to detect RD-NMR signal down to
$\mathrm{B}=1.25\mathrm{T}$
(3.5T) in high-mobility (low-mobility) device. All RD-NMR signals exhibit threefold spectra attributed to electric quadrupole interaction. We observe that the separation between central transition and its satellite at
$\Delta \mathrm{f}\approx 20\mathrm{kHz}$
remains unaffected by the magnetic variation, while the NMR linewidths decreases proportional to the applied magnetic field. Gaussian fitting of the central transition shows the NMR linewidth approaching the lowest limit of 1kHz correspond to GaAs nuclear dipole interaction as the magnetic field decrease to
$\mathrm{B}=1.25\mathrm{T}$
.