Classical trajectories in quantum transport at the band center of bipartite lattices with or without vacancies

TL;DR

This paper investigates quantum transport anomalies at the band center of bipartite lattices with vacancies, highlighting the role of chiral symmetry and eigenstate structure in phenomena like absence of weak localization and binary transmission.

Contribution

It reveals how chiral symmetry and state degeneracy lead to classical-like trajectories and unusual transport properties in bipartite lattices with vacancies.

Findings

No weak localization effect observed.

Transmission is either one or zero with single-channel leads.

Eigenstates form classical trajectories unaffected by vacancies.

Abstract

Here we report on several anomalies in quantum transport at the band center of a bipartite lattice with vacancies that are surely due to its chiral symmetry, namely: no weak localization effect shows up, and, when leads have a single channel the transmission is either one or zero. We propose that these are a consequence of both the chiral symmetry and the large number of states at the band center. The probability amplitude associated to the eigenstate that gives unit transmission ressembles a classical trajectory both with or without vacancies. The large number of states allows to build up trajectories that elude the blocking vacancies explaining the absence of weak localization.