LAUSR

We investigate the anharmonic effects in Bi2Se3 crystals using femtosecond transient optical spectroscopy at 5–280 K. The reflectivity time series consist of exponential decay due to hot carriers and decaying oscillations due to the A 1 g 1 phonon vibration. Vibration frequency and dephasing time of this optical phonon mode are obtained as a function of temperature, decreasing with increasing temperature; both the red shift in frequency and the increased dephasing rate induced by heating can be well described using the anharmonicity model including lattice thermal expansion and phonon-phonon coupling.We investigate the anharmonic effects in Bi2Se3 crystals using femtosecond transient optical spectroscopy at 5–280 K. The reflectivity time series consist of exponential decay due to hot carriers and decaying oscillations due to the A 1 g 1 phonon vibration. Vibration frequency and dephasing time of this optical phonon mode are obtained as a function of temperature, decreasing with increasing temperature; both the red shift in frequency and the increased dephasing rate induced by heating can be well described using the anharmonicity model including lattice thermal expansion and phonon-phonon coupling.