A mechanism for cutting carbon nanotubes with a scanning tunneling microscope

We discuss the local cutting of single-walled carbon nanotubes by a voltage pulse to the tip of a scanning tunneling microscope. The tip voltage (\ V \ greater than or equal to 3.8 V) is the key physical quantity in the cutti ng process. After reviewing several possible physical mechanisms we conclud e that the cutting process relies on the weakening of the carbon-carbon bon ds through a combination of localized particle-hole excitations induced by inelastically tunneling electrons and elastic deformation due to the electr ic field between tip and sample. The carbon network releases part of the in duced mechanical stress by forming topological defects that act as nucleati on centers fur the formation of dislocations that dynamically propagate tow ards bond-breaking.