  The low-temperature quasi-universal behavior of amorphous solids has been
attributed to the existence of spatially-localized tunneling defects found in
the low-energy regions of the potential energy landscape. Computational models
of glasses can be studied to elucidate the microscopic nature of these defects.
Recent simulation work has demonstrated the means of generating stable glassy
configurations for models that mimic metallic glasses using the swap Monte
Carlo algorithm. Building on these studies, we present an extensive exploration
of the glassy metabasins of the potential energy landscape of a variant of the
most widely used model of metallic glasses. We carefully identify tunneling
defects and reveal their depletion with increased glass stability. The density
of tunneling defects near the experimental glass transition temperature appears
to be in good agreement with experimental measurements.
