NMR of a single nuclear spin detected by a scanning tunnelling microscope

Abstract

We detect a single spin nuclear magnetic resonance (NMR) by monitoring the intensity modulations of a selected hyperfine line in the electron spin resonance (ESR) spectrum. We analyse the power spectrum of the corresponding hyperfine intensity and obtain the nuclear magnetic resonance (NMR) spectrum. Our process also demonstrates ionization of a molecule with the bias voltage of a Scanning Tunnelling Microscope (STM), allowing detection of NMR even in molecules that are non-radical in their neutral state. We have observed this phenomenon in four types of molecules: toluene, triphenylphosphine, TEMPO and adenosine triphosphate (ATP) showing NMR of ${}^1$H, ¹³C, ³¹P and ¹⁴N nuclei. The spectra are detailed and show signatures of the chemical environment, i.e. chemical shifts. A theoretical model to account for these data is outlined.