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arXiv · 1804.09308

Coherent Dirac plasmons in topological insulators

Richarj Mondal·Akira Arai·Yuta Saito·Paul Fons·Alexander V. Kolobov·Junji Tominaga·Muneaki Hase
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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 $A^2_{1g}$ 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 $\leq$200 fs. The asymmetry parameter could be well described by the TTM for $\geq$200 fs, therefore suggesting the coherence time of the Dirac plasmon is $\approx$200 fs.

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Richarj Mondal, Akira Arai, Yuta Saito, Paul Fons, Alexander V. Kolobov, Junji Tominaga, Muneaki Hase. 2018-04-25. Coherent Dirac plasmons in topological insulators. https://doi.org/10.1103/physrevb.97.144306

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