Surface collective modes in the topological insulators Bi${}_2$Se${}_3$ and Bi${}_{0.5}$Sb${}_{1.5}$Te${}_{3-x}$Se${}_x$

Abstract

We used low-energy, momentum-resolved inelastic electron scattering to study surface collective modes of the three-dimensional topological insulators Bi${}_2$Se${}_3$ and Bi${}_{0.5}$Sb${}_{1.5}$Te${}_{3-x}$Se${}_x$. Our goal was to identify the "spin plasmon" predicted by Raghu and co-workers [S. Raghu, et al., Phys. Rev. Lett. 104, 116401 (2010)]. Instead, we found that the primary collective mode is a surface plasmon arising from the bulk, free carrers in these materials. This excitation dominates the spectral weight in the bosonic function of the surface, $\chi "(\text{q},\omega )$, at THz energy scales, and is the most likely origin of a quasiparticle dispersion kink observed in previous photoemission experiments. Our study suggests that the spin plasmon may mix with this other surface mode, calling for a more nuanced understanding of optical experiments in which the spin plasmon is reported to play a role.

5 pages, 4 figures

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• Three dimensional topological invariants for time reversal invariant Hamiltonians and the three dimensional quantum spin Hall effect
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Cited by in corpus (17)

• Surface vibrational modes of the topological insulator Bi${}_2$Se${}_3$ observed by Raman spectroscopy
• Finite momentum Cooper pairing in 3D topological insulator Josephson junctions
• Anomalous Acoustic Plasmon Mode from Topologically Protected States
• Chiral Spin Mode on the Surface of a Topological Insulator
• Crossover of Charge Fluctuations across the Strange Metal Phase Diagram
• Optimization of the growth of the van der Waals materials Bi2Se3 and (Bi0.5In0.5)2Se3 by molecular beam epitaxy
• Tunable Intrinsic Plasmons due to Band Inversion in Topological Materials
• Effective hydrodynamic field theory and condensation picture of topological insulators
• Topologically Nontrivial Interband Plasmons in Type-II Weyl Semimetal MoTe${}_2$
• Controlling surface charge and spin density oscillations by Dirac plasmon interaction in thin topological insulators
• Plasmons in topological insulator cylindrical nanowires
• Strong coupling between a topological insulator and a III-V heterostructure at terahertz frequency
• Geometric Effect of High-Resolution Electron Energy Loss Spectroscopy on the Identification of Plasmons: An Example of Graphene
• Vibrational Properties of the Bi2Se3 Orthorhombic Metastable Phase
• The anomalous spin texture as the probe for interactions in $B{i}_{2-y}S{b}_{y}S{e}_{x}T{e}_{3-x}$
• Chiral edge plasmons in quantum anomalous Hall insulators
• In-Plane Plasmon Coupling in Topological Insulator Bi${}_2$Se${}_3$ Thin Films