Temperature-dependent coherent phonon dynamics in Bi₂Te₃

In this work, temperature-dependent(78K~290K) coherent phonon dynamics in topological insulator Bi₂Te₃ are investigated. Four coherent phonon types(A_1g¹, A_1g², E_g, coherent acoustic phonon) with strong temperature dependency are observed in transmission pump-probe spectroscopy at low temperature(78K, 90K).These could be attributed to temperature dependent gradient force which resulting in the coherent phonons generation. Especially, lifetime of around 2.87ps for E_g phonon mode is observed for the first time.The depressing signal of reflective pump probe due to the enhancing absorption of surface state for thin film topological insulator will be accordingly increasing as temperature cooling is proposed.