Plasmon excitations in nuclear magnetic resonance

A theory is presented to account for the recently observed anomalous peak in the nuclear magnetic relaxation rate $(1/T_1)$ in n-doped InSb. The magnitude of the magnetic field at the peak has been found to satisfy the equation ${\mathrm{\omega }}_s={\mathrm{\omega }}_p$, where ${\mathrm{\omega }}_s$ and ${\mathrm{\omega }}_p$ is the spin-flip energy and plasma frequency of the electrons, respectively. Furthermore, the peak occurs at a field such that only the spin-up, lowest Landau level is occupied (at $T=\mathit{0}°K$). Our theory discusses the anomalous peak as being due to plasmon absorption and emission by electrons as an intermediate step in the mutual electron-nucleus spin-flip process and predicts a logarithmic singularity in $(\mathit{1}/T_1)$ at ${\mathrm{\omega }}_s={\mathrm{\omega }}_p$.