Single-shot readout and coherent driving of nuclear spins in a single on-surface atom

Nuclear spins of individual on-surface atoms provide a promising platform for investigating how microscopic interactions determine effective spin Hamiltonians. In these systems, broken inversion symmetry at the surface, strong crystal fields, and spin-orbit coupling can substantially modify the hyperfine interaction between electronic and nuclear spins. Combined with scanning tunneling microscopy (STM), this sensitivity offers the possibility of tuning the hyperfine coupling through atom manipulation, enabling direct studies of nuclear-spin relaxation and decoherence at the single-atom level. While recent works have identified nuclear spins in individual atoms on surfaces using STM with electron spin resonance (ESR), their time- resolved dynamics and coherent control remain unexplored. In this talk, I will present our recent work on the nuclear spins of 47Ti and 49Ti isotopes (S = 1/2; I = 5/2 and 7/2, respectively) adsorbed on MgO/Ag(100) using ESR-STM.

We first achieve single-shot readout of the nuclear spin by applying radio-frequency pulses that drive ESR only for a selected nuclear-spin state and probing the presence or absence of an ESR response. This scheme enables time-resolved measurements of the nuclear spin state, revealing its lifetime on the order of seconds. We further demonstrate that the nuclear spin can be pumped and relaxed by DC spin-polarized tunneling current and by ESR driving, mediated by flip-flop interactions between the nuclear and electronic spins. In addition, we perform electron-nuclear double resonance by driving nuclear magnetic resonance transitions and probing them via the ESR signal at magnetic fields up to 1.4 T. These results establish ESR-STM as a powerful approach for probing and controlling individual nuclear spins on surfaces, offering new opportunities to explore how local symmetry, crystal fields, and spin-orbit coupling shape nuclear-spin dynamics at the single-atom level.