⁷⁷Se Nuclear Magnetic Resonance Study of the Surface Effect in Topological Insulator Bi₂Se₃ Nanoparticles

We have carried out ⁷⁷Se nuclear magnetic resonance (NMR) measurements in order to probe the surface state of topological insulator Bi₂Se₃ nanoparticles physically mixed with insulating Al₂O₃ nanoparticles. Two distinct peaks in the NMR spectra were separately assigned to the surface and the bulk regions in the samples with different mixing ratios, manifesting an increase in the surface effect.