NMR in a point contact device

Resistively-detected and ultra-sensitive nuclear magnetic resonance (NMR), which is suitable for high-mobility semiconductor hetero and nanostructures, has been developed. Fractional quantum hall physics enables us to dynamically polarize nuclear spins in a two-and one-dimensional channel and to detect the nuclear spin polarization by measuring the channel resistance. When an alternating magnetic field is applied to the channel, the coherent oscillation occurs for the nuclear spins that resonate with this magnetic field, resulting in the channel resistance oscillation. For a point contact device, all possible coherent oscillations have been successfully detected between two levels from four nuclear spin states of I=3/2 nuclei for both Ga and As. The number of nuclei in the point contact region is under 10⁸, witch is 3 to 5 orders of magnitude smaller than the sensitivity limit of standard NMR technology. Furthermore, a relaxation of nuclear spins has been used as a sensitive detector of electron spin states.