Working together, Professors Mitrovic and Marston and their graduate student have developed a technique called resistively detected nuclear magnetic resonance (RDNMR) that can be used to investigate the behavior of electron spins in topological insulators (TIs) with strong spin-orbit coupling. In these TIs, electron spins are locked to their momentum, making direct manipulation with microwaves impossible. However, RDNMR can be employed to probe the helical nature of surface conducting states in TIs. In this technique, a radio frequency (RF) field is applied to reorient nuclear spins, which then interact with electronic spins through the hyperfine interaction. This modulation of the electron spin affects the conductance, leading to changes at nuclear resonance frequencies. The direction of the applied magnetic field with respect to the helicity of the electrons influences the conductivity and provides insight into the nature of the conductive edge or surface states. Furthermore, their findings suggest that RDNMR can not only probe TI states but also enable the coherent manipulation of topologically protected states using RF control of nuclear spins, which could be valuable for future device applications.
This work has been published in Physical Review B. The article can be found here.