Electron orbital valves made of multiply connected armchair carbon nanotubes with mirror-reflection symmetry: tight-binding study

Using the tight-binding method and the Landauer-Buettiker conductance formalism, we demonstrate that a multiply connected armchair carbon nanotube with mirror-reflection symmetry can sustain an electron current of the π-bonding orbital while suppressing that of the π-antibonding orbital over a certain energy range. Accordingly, the system behaves like an electron orbital valve and it may be used as a scanning tunnelling microscope to probe pairing symmetry in d-wave superconductors or even orbital ordering in solids which is believed to occur in some transition-metal oxides