In this study, sub-angstrom spatial resolution is achieved in mapping and
spectroscopy of atoms and bonds within polygonal grain boundaries (GBs) of
graphite using Scanning Tunneling Microscopy (STM). Robust van Hove
singularities (VHS) are observed in addition to edge states under ambient
conditions. The bias-dependent nature of these states reveals metallic traits
of GB, through the charge accumulation and dissipation of localized electronic
states. Utilizing a surface elastic deformation technique induced by STM tip
allows pico-pinching of the GB, providing insights into its mechanical strength
as well as in-situ strain-induced modification of their unique spectroscopy,
revealing a tendency toward flattening of the electronic energy band
dispersion. An initial atomic-level experimental technique of probing
spin-polarized magnetic states is demonstrated, suggesting different densities
for spin-up and spin-down states within a spin-degenerate band structure
potentially applicable in spin transport or quantum spin sensing.Comment: Submitte