Origin of coherent phonons in Bi2Te3 excited by ultrafast laser pulses
Date of this Version8-26-2013
Wang, Yaguo; Guo, Liang; Xu, Xianfan; Pierce, Jonathan; and Venkatasubramanian, Rama, "Origin of coherent phonons in Bi2Te3 excited by ultrafast laser pulses" (2013).
Femtosecond laser pulses are used to excite coherent optical phonons in single crystal Bi2Te3 thin films. Oscillations from low-and high-frequency A(1g) phonon modes are observed. A perturbation model based on molecular dynamics reveals various possibilities of phonon generation due to complex interactions among different phonon modes. In order to elucidate the process of phonon generation, measurements on thin films with thicknesses below the optical absorption depth are carried out, showing that a gradient force is necessary to excite the observed A(1g) phonon modes, which provides a refined picture of displacive excitation of coherent phonon.