Theoretical analysis of single electron spin surface detections

The ultimate spintronic devices based on electron spins will utilize a single electron as one quantum bit, thus spatial detections of a single electron become essential. This paper presents a theoretical analysis of the unpaired single electron spin detection with considerations of spin noises and coherent spontaneous emissions. The classic electron spin resonance spectrometer uses a high Q-factor tuned microwave cavity, which is capable of detecting the free electron spin density in the range from 10⁶ to 10¹¹ spins. The key for single electron spin detection relies on the detections of the energy exchange between the electron and microwave virtual photons. Furthermore, for such a tiny energy, the free induction decay signal will be overwhelmed by the surrounding noises. The possibility of increasing the sensitivity of the ESR spectrometer to one single spin using magnetic field modulation is presented.