【摘 要】
：
The ultrafast dynamics ofphotoexcited carriers and coherent phonons in ultrathin Bi2Te3 thermoelectric films are studied through transient differential transmission spectroscopy.An ultralow frequency coherent optical phonon at 0.16 THz emerges,especially
【机 构】
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State Key Laboratory of Optoelectronic Materials and Technologies,School of Physics,Sun Yat-sen Univ
【出 处】
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中国科学：物理学 力学 天文学（英文版）
论文部分内容阅读
The ultrafast dynamics ofphotoexcited carriers and coherent phonons in ultrathin Bi2Te3 thermoelectric films are studied through transient differential transmission spectroscopy.An ultralow frequency coherent optical phonon at 0.16 THz emerges,especially in ultrathin films,and it is ascribed to interlayer breathing modes.It can divide the ultrathin films into two groups which have out-of-phase vibration along the normal of a film plane,causing a destructive interference between in-plane propagating thermal waves in the two groups of quintuple layers,and thus possibly reducing the thermal conductivity of the ultrathin films.The excitation power dependence ofultrafast dynamics reveals carrier-carrier scattering dominating thermalization,which provides a microscopic understanding of the reported high electrical conductivity and anomalously high power factor of ultrathin Bi2Te3 films at room temperature.
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