Invited Speaker
Prof. Aristides D. Zdetsis

Prof. Aristides D. Zdetsis

Head Molecular Engineering Laboratory
Division of Theoretical and Mathematical Physics,Astronomy and Astrophysics.
Department of Physics, University of Patras
26500, Patra, Greece
Speech Title: Topological edge/end states in narrow and wider armchair graphene nanoribbons: New and Novel Effects.

Abstract: It is illustrated that in atomically precise armchair graphene nanoribbons (AGNRs) of finite length L, synthesized using molecular precursors, n pairs (occupied/unoccupied) of topological end-states can develop, comprising their frontier molecular orbitals (MOs), which are localized at their zigzag ends. These states appear at critical length(s) Lc at which a metal-insulator-like transition takes place, associated with a peak in the density of states (DOS) at the fermi level Ef, and a rather abrupt change in conductivity and energy gap. As a result, we can have various types of “bulk” and “surface” gaps. The number n of the pairs of topological states depends on the width W of the AGNRs, measured by the number of end zigzag rings Z (W=2Z=1) where Z, depending on the AGNRs’ type, is given by Z= 3n, 3n±1 n=1, 2, 3, … Thus, wider AGNRs (n>1) are expected to have a larger number of end-states. However, the corresponding “transitions” are not expected to be so abrupt as for the thinnest n=1, W=5 AGNRs, due to quantum confinement. Yet, surprisingly enough, we have recently found that in wider n=2 AGNRs (W=13, 15) at large enough lengths, abrupt (and intense) jumps in conductivity and band gaps can be developed, due to (mainly) MO interactions of the multiple end-states localized in the same region around the zigzag ends. As a result, (constructive) quantum interference effects can result (CQI) with profound possibilities for applications related with transport (conductivity) and electronic properties (bandgap) functionalization in nanoelectronics and nanoscience.

Keywords: Atomically precise AGNRs, Topological end/edge states, Energy gaps of AGNRs, Quantum Interference.

Biography: Aristides Zdetsis is professor emeritus at the Department of Physics University of Patras Greece, where he also serves as head of the local molecular engineering laboratory. Prof Zdetsis is a fellow of IAAM and a Vebleo fellow. He is currently involved with theoretical and Computational work in graphene and graphene-based 2D materials and structures. He has written more than 155 scientific articles, from which almost half are monographies. He has written 4 books (in Greek for the Greek open university and university of Patras) and 1 under preparation (in English on graphene). He has performed more than 160 verified reviews (publons) and has given more than 50 invited (and keynote) presentations in international and topical conferences.