Coherent Dirac plasmons in topological insulators

Abstract

We explore the ultrafast reflectivity response from photo-generated coupled phonon-surface Dirac plasmons in Sb${}_2$Te${}_3$ topological insulators several quintuple layers thick. The transient coherent phonon spectra obtained at different time frames exhibit a Fano-like asymmetric line shape of the $A_{1g}^2$ mode, which is attributed to quantum interference between continuum-like coherent Dirac-plasmons and phonons. By analyzing the time-dependent asymmetric line shape using the two-temperature model (TTM), it was determined that a Fano-like resonance persisted up to $\approx$1 ps after photo-excitation with a relaxation profile dominated by Gaussian decay at $\le$200 fs. The asymmetry parameter could be well described by the TTM for $\ge$200 fs, therefore suggesting the coherence time of the Dirac plasmon is $\approx$200 fs.

arXiv comment7 pages, 5 figures

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Cited by in corpus (5)

• Localized Plasmons in Topological Insulators
• Role of matrix elements in the time-resolved photoemission signal
• Photon Energy Dependence of Kerr Rotation in Chalcogenide Superlattices
• Ultrafast scattering dynamics of coherent phonons in Bi${}_{1-x}$Sb${}_x$ in the Weyl semimetal phase
• Role of interlayer shear phonons on lattice symmetry switching in the transition metal dichalcogenide WTe${}_2$