Abstract
We report upon observation of a transient Fano resonance, a quantum interference between coherent phonon and Dirac plasmons, that persisted for up to 1 picosecond in the topological insulator Sb2Te3 investigated using coherent phonon spectroscopy.
Highlights
Fano resonances in optical spectra are one of the most intriguing quantum mechanical processes in solid state physics [1]
These peaks are assigned to the A1g1 and A1g2 optical phonon modes, respectively, as indicated in Fig. 1(b), which is in good agreement with those observed by Raman measurements [5]
At near zero time delay, the wave function of the continuum, i.e., Dirac plasmons in SS2 band, and the bulk coherent phonon (A1g2 mode) are strongly coupled to each other leading quantum interference, resulting in a Fano-like line shape. The coupling between these two states decreases with increasing time delay, as the photogenerated coherent Dirac plasmons dephase within ≈1 ps through the energy distribution within the SS2 band [11]
Summary
Fano resonances in optical spectra are one of the most intriguing quantum mechanical processes in solid state physics [1]. They occur when a discrete optical transition overlaps with continuum states and interference occurs. The phonon properties in TIs have been extensively studied using Raman scattering measurements [5], the electronphonon interaction in the time-domain is less well understood in TIs. In this work, we report on the dynamics of coherent phonons [6], generated by ultrashort laser pulses in a prototypical TI, Sb2Te3, and discuss quantum interference between discrete (phonons) and continuum states (Dirac-plasmons)
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