Ultrafast transport-mediated homogenization of photoexcited electrons governs the softening of the A(1g) phonon in bismuth

Article

关键词: PARTIALLY COHERENT;    DYNAMICS;    CARRIERS;   

DOI  :  10.1103/PhysRevB.106.014315

来源: SCIE

【 摘 要 】

In order to determine the role of nonthermal 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-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(1g) phonon mode as a function of the incident fluence, film thickness, and probe wavelength in the range 580-700 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(1g) phonons in Bi. For Bi films up to 50 nm thickness a homogeneous excitation due to the ultrafast transport of hot charge carriers is observed, limited by a carrier penetration depth of 60 nm independent of the totally deposited laser energy.

【 授权许可】

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