Identifying Klein tunneling signatures in bearded Su-Schrieffer-Heeger lattices from bent flat bands

Su-Schrieffer-Heeger (SSH) lattices have helped to understand key concepts of topological insulators. In this paper, we study the transmission properties of $pn$ junctions of bearded SSH lattices forming a bipartite structure. From a tight-binding approach, we found the condition on the hopping parameters of the Bloch Hamiltonian to depict the electron behavior as a massive pseudospin-one particle in quasi-one-dimensional systems. It is possible to design the band structure of these lattices by tuning the on-site energy and hopping parameters. The characteristic flat band of pseudospin-one systems can be bent by the staggered potential of the bottom atom in the bearded edge. Transmissions in bipartite bearded SSH lattices are obtained from exact matching conditions by considering the full Bloch Hamiltonian of tight-binding to nearest neighbors. We explore interband transmissions from the bent flat band to the valence one of a bipartite structure, where Klein tunneling can be obtained depending on the hopping parameter associated with the bearded edge. Identifying Klein tunneling signatures is feasible in artificial lattices such as photonic lattices, elastic resonators, topolectric circuits, or quantum dot arrangements. On the other hand, the study of Klein tunneling in polyatomic molecules may contribute to advance in one-dimensional transistors.