Observing field-induced effects in scanning tunneling microscope junction through lifetimes of resonant electrons

Field emission resonance (FER) arises from the coupling of field-emitted electrons from the tip of scanning tunneling microscope (STM) with quantized states formed in the STM junction. The average lifetime of FER electrons, reflected in the linewidth according to the uncertainty principle, has been rarely explored. Here, we review our recent findings on using FER linewidth to probe field-induced effects within STM junction, including quantum trapping occurring on MoS₂and Ag(100) surfaces, as well as the attractive deformation on graphite surfaces. We demonstrate that the FER linewidth on MoS₂and Ag(100) surfaces can vary by up to tenfold, which is an outcome of the quantum trapping coupled with mechanisms such as correlated two-electron tunneling through exchange interaction, energy gap above the vacuum level, spin flip, light emission, and the Pauli exclusion principle. This substantial FER linewidth variation is absent on the Ag(111) surface due to the lack of an energy gap above the vacuum level. The finite lifetimes of resonant electrons signify that the FER wave function decays at a rate proportional to the FER linewidth. We find that this decay rate remains nearly unchanged with increasing FER electric field on Ag(111) surface, while it rises with field strength on graphite. This marked difference arises from the more pronounced attractive deformation of graphite, with the deformed top layer resembling monolayer graphene.