Localized plasmons in topological insulators
Source abstract
Abstract
We investigate in a fully quantum-mechanical manner how the many-body excitation spectrum of topological insulators is affected by the presence of long-range Coulomb interactions. In the one-dimensional Su-Schrieffer-Heeger model and its mirror-symmetric variant strongly localized plasmonic excitations are observed which originate from topologically nontrivial single-particle states. These ``topological plasmons'' inherit some of the characteristics of their constituent topological single-particle states, but they are not equally well protected against disorder due to the admixture of nontopological bulk single-particle states in the polarization function. The strength of the effective Coulomb interactions is also shown to have strong effects on the plasmonic modes. Furthermore, we show how external modifications via dielectric screening and applied electric fields with distinct symmetries can be used to study topological plasmons, thus allowing for experimental verification of our atomistic predictions.
Source: openalex_inverted_index · Quality: baseline
Research context
OpenAlex topics: Topological Materials and Phenomena · Graphene research and applications · Quantum and electron transport phenomena
SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.
Affiliations
Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089-0484, USA
Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, Netherlands
Funding
U.S. Department of Energy · Alexander von Humboldt-Stiftung
References (32)
Show source-provided references
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24. The number of edge and interface states can also be understood in terms of valence-bond decorations corresponding to the different states. For the simple SSH model in the topologically trivial state [blue in Fig. 1], the resulting valence bond solid connects every site with a neighbor, resulting in a perfect product state of valence bonds. In contrast, in the valence-bond decoration corresponding to the topological phase [red in Fig. 1], the two outer bonds remain uncoupled, i.e., dangling bonds, leading to the observed s1 and s2 mid-gap zero-energy states. For the m-SSH model with two neighboring strong bonds at the central mirror interface [blue in Fig. 1], the resulting three-site strongly coupled object is a nonbonding state, whereas the remaining states are valence bonds. This results in a localized state at the interface. Finally, in the opposite decoration of the m-SSH chain [red in Fig. 1], there are dangling bonds at each end of the chain as well as at the mirror interface, resulting in localized zero-energy states at each of these positions.
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30. In deriving Eq. (13), we assume that the tight-binding wave functions are real and all topological states have zero energy and occupation number 1/2.
31. The IPR of a normalized N-dimensional vector ψ is calculated via IPR=∑iN|ψi|4, where i is the index of the components. An increased IPR indicates a stronger localized distribution. We calculate the electronic IPR (e-IPR) from the eigenvector of the Hamiltonian and the plasmonic IPR (p-IPR) from the eigenvector of the dielectric matrix derived from χ0full/topo (p-IPRfull/topo).
32. The R-STD is defined by the square root of the second central moment of the averaged EELS, divided by the unperturbed excitation energy.