Dynamic nuclear self-polarization with circularly polarized light.

Lattice nuclei of III-V type semiconductors can be self-polarized through the contact hyperfine interaction with artificially excited conduction electrons at extremely low temperatures. In the self-polarization process, a positive feedback between the nuclear magnetization and the expansion of the energy splitting of the conduction electron states due to this nuclear magnetization takes an essential role. Extending the original theoretical work on the self-polarization with linearly polarized (LP) light by Dyakonov and Perel,1 we examined the effect of the circularly polarized (CP) light on the phenomenon of the nuclear self-polarization. While no polarization is obtained with LP light above the critical temperature, the nuclear polarization is enhanced also above the critical temperatures with CP light. More important finding in the application of CP light is that the direction of the nuclear polarization can be controlled by the orientation of the excited conduction-electron polarization, which is easily manipulated by changing the degree of polarization of the excitation light. Related to this polarization change, it is also remarked that the nuclear polarization shows a hysteresis phenomenon below the critical temperature when the degree of the electron polarization is swept up and down. [ABSTRACT FROM AUTHOR]