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

TL;DR

This study demonstrates that mirror-symmetric multiply connected armchair carbon nanotubes can selectively conduct specific electron orbitals, functioning as orbital valves with potential applications in probing superconducting pairing symmetry and orbital ordering.

Contribution

We introduce a tight-binding model showing orbital-selective conductance in symmetric nanotube structures, revealing a new orbital valve mechanism.

Findings

Selective conductance of $\pi$-bonding orbitals over antibonding ones.

Potential use as a scanning tunneling microscope probe.

Orbital valve behavior depends on energy range.

Abstract

Using the tight-binding method and the Landauer-B\"{u}ttiker conductance formalism, we demonstrate that a multiply connected armchair carbon nanotube with a mirror-reflection symmetry can sustain an electron current of the $\pi$-bonding orbital while suppress that of the $\pi$-antibonding orbital over a certain energy range. Accordingly, the system behaves like an electron orbital valve and may be used as a scanning tunneling 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.