论文标题
超快传输介导的光激发电子的均质化控制bismuth中$ a_ \ mathrm {1g} $ phonon的软化
Ultrafast transport mediated homogenization of photoexcited electrons governs the softening of the $A_\mathrm{1g}$ phonon in bismuth
论文作者
论文摘要
为了确定热载体非热运输的作用，这对于凝结物中的能量耗散是决定性的，我们在$ 7-197 \ Mathrm {nm} $厚Bi（111）胶片上表达在Si（111）上表达生长（111）。我们监视了傅立叶振幅的行为和相干$ a_ \ mathrm {1G} $声子模式的中心频率，作为入射通量，膜厚度和探测波长的函数，范围为$ 580 -700 \ Mathrm {nm} $。遵循光激发后的频率红移用作强大数量，以确定bi中相干$ a_ \ mathrm {1g} $ phonons的相干激发机理的激发载体的有效分布。对于BI胶片最高$ 50 \ MATHRM {nm} $厚度，厚度是由于热电载体的超快传输而引起的同质激发，受到载体渗透深度为$ 60 \ MATHRM {nm} $独立于完全沉积的激光能量。
In order to determine the role of non-thermal transport of hot carriers which is decisive for the dissipation of energy in condensed matter we performed time-resolved broadband femtosecond transient reflectivity measurements on $7-197 \mathrm{nm}$ thick Bi(111) films epitaxially grown on Si(111). We monitored the behavior of the Fourier amplitude and the central frequency of the coherent $A_\mathrm{1g}$ phonon mode as function of the incident fluence, film thickness, and probe wavelength in the range of $580 -700 \mathrm{nm}$. The frequency redshift that follows photoexcitation was used as a robust quantity to determine the effective distribution of excited carriers that governs the displacive excitation mechanism of coherent $A_\mathrm{1g}$ phonons in Bi. For Bi films up to $50 \mathrm{nm}$ thickness a homogeneous excitation due to the ultrafast transport of hot charge carriers is observed, limited by a carrier penetration depth of $60 \mathrm{nm}$ independent of the totally deposited laser energy.
