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oe1(光电查) - 科学论文

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  • Anharmonicity of Bi <sub/>2</sub> Se <sub/>3</sub> revealed by fs transient optical spectroscopy

    摘要： We investigate the anharmonic effects in Bi2Se3 crystals using femtosecond transient optical spectroscopy at 5–280 K. The re?ectivity time series consist of exponential decay due to hot carriers and decaying oscillations due to the A1 1g 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.

    关键词： Bi2Se3,femtosecond transient optical spectroscopy,phonon dynamics,anharmonicity,thermal expansion,phonon-phonon coupling

    更新于2025-09-11 14:15:04

  • Stability of the light-induced hidden charge density wave state within the phase diagram of

    摘要： The femtosecond transient optical spectroscopy is employed to study the relaxation dynamics of the equilibrium and hidden metastable charge-density-wave states in single crystals of 1T-TaS2?xSex as a function of the Se doping x. Similar to pristine 1T-TaS2, the transition to a hidden phase is observed at low temperature after a quench with a single 50 fs laser pulse, in the commensurate Mott phase up to x = 0.6. The photo-induced hidden-phase formation is accompanied by a notable change in the coherent phonon spectra, and particularly the collective amplitude mode. While the temperature stability of the hidden phase is only slightly dependent on the Se content, the creation-threshold ?uence strongly increases with Se content from 1 to ～4 mJ/cm2, which is attributed predominantly to the change in optical absorption coef?cient at the laser excitation wavelength, and not an increased barrier of the hidden state with increasing Se.

    关键词： hidden phase,charge-density-wave states,1T-TaS2?xSex,coherent phonon spectra,femtosecond transient optical spectroscopy

    更新于2025-09-10 09:29:36