电子和声子对金热反射光谱的贡献
Differentiating Contributions of Electrons and Phonons to the Thermoreflectance Spectra of Gold
摘要：
为了更好地理解温度对金属光学性质的许多影响，我们从实验和理论上量化了电子与声子对金的热反射光谱的贡献。我们进行了一系列的泵浦/探测测量纳米Pt/Au双层膜在400和1000 nm之间的波长。在所有波长下，我们发现声子温度的变化，而不是电子温度，是金的热反射率的主要贡献者。由于d-态和费米能级之间的带间跃迁，热反射率对~480 nm波长处的电子温度最敏感。在近红外区，电子温度只占总热反射率的2%。我们还从第一性原理计算了Au的热反射光谱。我们的计算进一步证实了声子温度主导Au的热反射率。Au的热反射率大部分是由于声子数对电子寿命的影响。
英文摘要：
To better understand the many effects of temperature on the optical properties of metals, we experimentally and theoretically quantify the electron vs. phonon contributions to the thermoreflectance spectra of gold. We perform a series of pump/probe measurements on nanoscale Pt/Au bilayers at wavelengths between 400 and 1000 nm. At all wavelengths, we find that changes in phonon temperature, not electron temperature, are the primary contributor to the thermoreflectance of Au. The thermoreflectance is most sensitive to the electron temperature at wavelength of ~480 nm due to interband transitions between d-states and the Fermi-level. In the near infrared, the electron temperature is responsible for only ~2% of the total thermoreflectance. We also compute the thermoreflectance spectra of Au from first principles. Our calculations further confirm that phonon temperature dominates thermoreflectance of Au. Most of Au's thermoreflectance is due to the effect of the phonon population on electron lifetime.
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