Fig. 1: Vibrational quantum coherence in Bi2Se3 driven by an intense single-cycle THz pulse above a threshold electric field.
From: Light control of surface–bulk coupling by terahertz vibrational coherence in a topological insulator
a Experimental schematics of the THz pump process in Bi2Se3 film. Intense THz pulses drive coherent phonon oscillations of the \({E}_{u}^{1}\) mode that strongly influence surface state transport. b THz electric field profile in the time domain, with peak field as large as 500 kV cm−1 and c broadband spectrum from 1 to 10 meV (pink shade). The static conductivity σ1(ω), shown together in c, exhibits Drude transport behavior superimposed to a bulk \({E}_{u}^{1}\) phonon mode resonance at ~8 meV (black solid circle). d The post-pump THz emission for various driving THz electric fields demonstrates a threshold-like behavior clearly observed above Eth ~180 kV cm−1. e Pump electric field dependence of the coherent phonon integrated spectral weight shows a significant increase above threshold Eth. Inset: Corresponding Fourier spectrum of time-domain THz emission driven by single-cycle THz pump with E-field of 500 kV cm−1.
