Abstract
Ultrafast dynamics of carriers and phonons in topological insulators Cu<sub><i>x</i></sub>Bi<sub>2</sub>Se<sub>3-<i>y</i></sub> (<i>x</i>=0, 0.1, 0.125, <i>y</i>=0, 1) was studied using femtosecond optical pump-probe spectroscopy. One damped oscillation was clearly observed in the transient reflectivity changes (Δ<i>R/R</i>), which is assigned to the coherent optical phonon (A<sub>1g</sub> <sup>1</sup>). According to the red shift of A<sub>1g</sub><sup>1</sup> phonon frequency, the Cu atoms in Cu<sub>x</sub>Bi<sub>2</sub>Se<sub>3</sub> crystals may predominantly intercalated between pair of the quintuple layers. Moreover, the carrier dynamics in the Dirac-cone surface state is significantly different from that in bulk state, which was investigated using optical pump mid-infrared (mid-IR) probe spectroscopy. The rising time and decay time of the negative component in Δ<i>R/R</i>, which is assigned to carrier relaxation in Dirac cone, is 1.62 ps and 20.5 ps, respectively.
Highlights
Topological insulators (TIs) [1,2,3,4,5,6,7,8] and two-dimensional (2D) materials such as graphene [9], MoS2, WS2, and MoSe2 [10] are of great interests because of their unique physical properties and applications
We report the ultrafast dynamics of carriers and phonons in topological insulator Bi2Se3, CuxBi2Se3 (x = 0, 0.1, 0.125) single crystals
By time-resolved pump-probe spectroscopy, one damped fast oscillation was clearly observed in the transient reflectivity changes (∆R/R) for
Summary
Topological insulators (TIs) [1,2,3,4,5,6,7,8] and two-dimensional (2D) materials such as graphene [9], MoS2, WS2, and MoSe2 [10] are of great interests because of their unique physical properties and applications. TIs have a spin degenerate and fully gapped bulk state but exhibit a spin polarized and gapless electronic state on the surface [8]. The issues associated with electron–phonon interaction, carrier lifetime, carrier dynamics, energy loss rate, and low-energy electronic responses are very important for optimizing device performance These ultrafast dynamic properties of the materials can be resolved by pump-probe spectroscopy. We provide a brief introduction to the materials, time-resolved pump-probe spectroscopy, and some ultrafast dynamic properties of Bi-based topological insulators
Sign-in/Register to view highlights & summary 
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call