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/T₁) in n-doped InSb. The magnitude of the magnetic field at the peak has been found to satisfy the equation ωₛ=ωₚ, where ωₛ and ωₚ 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=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 (1/T₁) at ωₛ=ωₚ.