Electrical Detection of Polarized Electronic Spins in Semiconductors at Room Temperature Using a Radio Frequency Coil

Abstract

This experiment shows the measurement of electronic spin polarization in bulk semiconductors using a sensitive rf coil. The basic idea is to excite the electrons from the valence band to the conduction band using a circularly polarized laser. Due to the strong spin orbit coupling in the valence band, a part of the angular momentum of the light is transferred to the electron which allows them to be spin polarized to certain degree of efficiency, for e.g. 50% for GaAs. The spins decay with a lifetime of about 50ps at 300K. In steady state, for a pump power of 100mW at 850nm, total number of spin polarized electrons ∼107 can be achieved in GaAs. These polarized electrons produce a weak magnetization which was modulated at a frequency of ∼2MHz. The time varying magnetic field generated was then detected by a sensitive tuned rf coil of Q‐factor ∼36.