Optical cooling of a nuclear spin system of a conductor in a weak oscillating magnetic field
Fleisher V.G., Dzhioev R.I., Zakharchenya B.P.
The spin temperature Θ of an η-type semiconductor was lowered to the range 10~4-10~3 °K with synchronous modulation of the circular polarization of the exciting laser beam and of the longitudinal magnetic field (which was lower than the local fields) at a frequency 30 kHz. The cooling was detected by the increase of the equilibrium nuclear polarization along the weak transverse field at positive and negative.