Here we present a simple extension to the age-old Kronig-Penney model, which is made to be bipartite by varying either the scatterer separations or the potential heights. In doing so, chiral (sublattice) symmetry can be introduced. When such a symmetry is present, topological chiral symmetry protected edge states are seen to exist in correspondence with the standard quantised Zak phase bulk invariant. This quantisation behaviour may also be observed within a 'gauge'-invariant on-diagonal matrix element of a unit eigenvalue equation. The solution proceeds through the conventional scattering formalism used to study the Kronig-Penney model, which does not require further tight-binding approximations or mapping into a Su-Schrieffer-Heeger model. The cases in which chiral symmetry is absent are then seen to not host topologically protected edge states, as verified by zero bulk invariants.
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http://dx.doi.org/10.1088/1361-648X/ab4d67 | DOI Listing |
Materials (Basel)
September 2024
School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0250, USA.
The Gauss chain is a one-dimensional quasiperiodic lattice with sites at zj=jnd, where j∈{0, 1, 2, …, N-1}, n∈{2, 3, 4, …}, and is the underlying lattice constant. We numerically study the formation of a hierarchy of minibands and gaps as increases using a Kronig-Penney model. Increasing empirically results in a more fragmented miniband and gap structure due to the rapid increase in the number of minibands and gaps as increases, in agreement with previous studies.
View Article and Find Full Text PDFJ Phys Chem Lett
August 2023
University of Innsbruck, Theoretical Chemistry Division Institute of General Inorganic and Theoretical Chemistry, Center for Chemistry and Biomedicine, Innrain 80-82, A-6020 Innsbruck, Austria.
In this work, a generalized, adapted Numerov implementation capable of determining band structures of periodic quantum systems is outlined. Based on the input potential, the presented approach numerically solves the Schrödinger equation in position space at each momentum space point. Thus, in addition to the band structure, the method inherently provides information about the state functions and probability densities in position space at each momentum space point considered.
View Article and Find Full Text PDFACS Nano
August 2022
Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
A theoretical ideal two-dimensional electron gas (2DEG) was characterized by a flat density of states independent of energy. Compared with conventional two-dimensional free-electron systems in semiconductor heterojunctions and noble metal surfaces, we report here the achievement of ideal 2DEG with multiple quantized states in few-layer InSe films. The multiple quantum well states (QWSs) in few-layer InSe films are found, and the number of QWSs is strictly equal to the number of atomic layers.
View Article and Find Full Text PDFJ Phys Condens Matter
May 2021
Department of Physics and Astronomy, School of Natural Sciences, Faculty of Science and Engineering, University of Manchester, Oxford Road, Manchester, M13 9PY, United Kingdom.
We study topological surface-plasmon-polaritons at optical frequencies in tri-harmonic diffraction gratings formed at a metal-dielectric interface. The latter are shown to well approximate a bipartite Kronig-Penney model. Topologically protected localised modes are then predicted to occur at the edges of the grating and at defects formed by the combination of two mirror antisymmetric corrugations, whose bulk invariant is a step-wise varying Zak phase in both cases.
View Article and Find Full Text PDFMolecules
March 2021
Laboratoire de Chimie Théorique, CNRS and Sorbonne University, 4 Place Jussieu, CEDEX 05, 75252 Paris, France.
Pauling described metallic bonds using resonance. The maximum probability domains in the Kronig-Penney model can show a picture of it. When the walls are opaque (and the band gap is large) the maximum probability domain for an electron pair essentially corresponds to the region between the walls: the electron pairs are localized within two consecutive walls.
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