Subgap tunneling through channels of polarons and bipolarons in chain conductors

TL;DR

This paper develops a theory for subgap tunneling in quasi-1D systems with a pseudogap, explaining how tunneling currents evolve from smearing the free electron gap to polaron and bipolaron tunneling.

Contribution

It introduces a theoretical framework for internal coherent tunneling in pseudogap regions of 1D conductors, including polarons and bipolarons, applicable to various materials.

Findings

Tunneling current-voltage characteristics evolve from gap smearing to polaron and bipolaron tunneling.

The theory applies to conjugated polymers, nanotubes, and quantum wires.

Potential extension to high-temperature superconductors in the undoped limit.

Abstract

We suggest a theory of internal coherent tunneling in the pseudogap region where the applied voltage is below the free electron gap. We consider quasi 1D systems where the gap is originated by a lattice dimerization like in polyacethylene, as well as low symmetry 1D semiconductors. Results may be applied to several types of conjugated polymers, to semiconducting nanotubes and to quantum wires of semiconductors. The approach may be generalized to tunneling in strongly correlated systems showing the pseudogap effect, like the family of High Tc materials in the undoped limit. We demonstrate the evolution of tunneling current-voltage characteristics from smearing the free electron gap down to threshold for tunneling of polarons and further down to the region of bi-electronic tunneling via bipolarons or kink pairs.