Interface-sensitive nuclear magnetic resonance at a semiconductor heterojunction using hyperpolarization
We demonstrate an interface-sensitive NMR in a semiconducting nanostructure, where an NMR signal from the minute heterojunction region of a model heterojunction structure (In$_{0.48}$Ga$_{0.52}$P/GaAs) is detected by using nuclear hyperpolarization created by optical pumping. The key to the detection is the use of minute lattice distortions occurring at the heterojunction due to the lattice mismatch, which enables us to create and localize hyperpolarization at the heterojunction and distinguish it from the other parts. In particular, the suppression of nuclear spin diffusion by the spatial variation in the strain and the resultant unexpectedly stable hyperpolarization at the heterojunction are the keys to successful detection.