Molecular Control of Floquet Topological Phase in Non-adiabatic Thouless Pumping

TL;DR

This paper explores how molecular modifications in trans-polyacetylene influence the nonadiabatic Floquet topological phase, using real-time density functional theory and Wannier functions to connect topological invariants with chemical concepts.

Contribution

It demonstrates molecular-level control of Floquet topological phases through chemical substitutions, linking topological invariants to valence bond descriptions.

Findings

Molecular substitutions affect the winding number and topological phase.

Wannier functions relate topological invariants to chemical bonding.

Topological pumping can be described as cyclic orbital transitions.

Abstract

Nonadiabatic Thouless pumping of electrons is studied in the framework of topological Floquet engineering, particularly focused on how changes to chemical moieties can control the emergence of the Floquet topological phase. We employ real-time time-dependent density functional theory to investigate the extent to which the topological invariant, the winding number, is impacted by molecular-level changes to trans-polyacetylene. In particular, several substitutions to trans-polyacetylene are studied to examine different effects on the electronic structure including mesomeric effect, inductive effect, and electron conjugation effect. Maximally-localized Wannier functions are employed to relate the winding number to the valence bond description by expressing the topological pumping as the transport dynamics of the localized Wannier functions. By further exploiting the gauge invariance of the quantum dynamics in terms of the minimal particle-hole excitations, the topological pumping of electrons can be also represented as a cyclic transition among the bonding and antibonding orbitals. Having connected the topological invariant to chemically intuitive concepts, we show the molecular-level control on the emergence of the Floquet topological phase, presenting us with a great opportunity for the intuitive engineering of molecular systems for such an exotic topological phase.