Kirby Robert J, Ferrenti Austin, Weinberg Caroline, Klemenz Sebastian, Oudah Mohamed, Lei Shiming, Weber Chris P, Fausti Daniele, Scholes Gregory D, Schoop Leslie M
Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States.
Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.
J Phys Chem Lett. 2020 Aug 6;11(15):6105-6111. doi: 10.1021/acs.jpclett.0c01377. Epub 2020 Jul 16.
The ultrafast optical response of nodal-line semimetals ZrSiS and ZrSiSe was studied in the near-infrared using transient reflectivity. The materials exhibit similar responses, characterized by two features, well-resolved in time and energy; the first decays after hundreds of femtoseconds, and the second lasts for nanoseconds. Using Drude-Lorentz fits of the materials' equilibrium reflectance, we show that these are well-represented by a sudden change of the electronic properties (increase of screening or reduction of the plasma frequency) followed by an increase of the Drude scattering rate. This directly connects the transient data to a physical picture in which carriers, after excitation into the conduction band, return to the valence band by sharing excess energy with the phonon bath, resulting in a hot lattice that relaxes through slow diffusive processes. The emerging picture reveals that the sudden electronic reorganization instantaneously modifies the materials' electronic properties on a time scale not compatible with electron-phonon thermalization.
利用瞬态反射率在近红外波段研究了节线半金属ZrSiS和ZrSiSe的超快光学响应。这些材料表现出相似的响应，其特征在于在时间和能量上都能很好分辨的两个特征；第一个特征在数百飞秒后衰减，第二个特征持续数纳秒。通过对材料平衡反射率进行德鲁德-洛伦兹拟合，我们表明这些特征可以很好地用电子性质的突然变化（屏蔽增加或等离子体频率降低）以及随后德鲁德散射率的增加来表示。这直接将瞬态数据与一种物理图像联系起来，在该图像中，载流子在被激发到导带后，通过与声子库共享多余能量回到价带，导致热晶格通过缓慢的扩散过程弛豫。新出现的图像表明，这种突然的电子重组在与电子-声子热化不兼容的时间尺度上瞬间改变了材料的电子性质。
