金属光电发射的等离子体辅助通道
Plasmonically assisted channels of photoemission from metals
摘要：
我们分析最近测量的非线性光电子能谱从银表面，揭示共振的能量不与所施加的光子能量的比例，但保持固定到多个体等离子体能量$\hbarω_p$以上的费米能级。为了阐明这些意想不到的和奇特的功能，我们调查的光谱产生的等离子体激元在固体中的光泵电子极化和它们的光电效应。通过结合二次响应形式主义计算的光电发射产额，非弹性电子散射的非微扰方法，和第一性原理计算的电子结构，我们证明了依赖于概率振幅的单和多等离子体激元激发的基本参数表征的光子脉冲和系统。由此产生的多激发光谱演变向截断等离子体相干态。用类似的概念解释了多光子激发电子极化产生等离子体激元。在此基础上，我们阐述了这样创建的真实等离子体激元作为补充锁频泵浦场的非爱因斯坦等离子体辅助通道的金属光电发射的情况。所建立的范例，使分配和评估所观察到的线性$\hbarω_p$ -和非线性$2\hbarω_p$ -电子产率从银。这种效应可以用于电子系统中光能转换的选择性滤波。
英文摘要：
We analyse recently measured nonlinear photoemission spectra from Ag surfaces that reveal resonances whose energies do not scale with the applied photon energy but stay pinned to multiples of bulk plasmon energy $\hbarω_p$ above the Fermi level. To elucidate these unexpected and peculiar features we investigate the spectra of plasmons generated in a solid by the optically pumped electronic polarization and their effect on photoemission. By combining quadratic response formalism for calculations of photoemission yield, a nonperturbative approach to inelastic electron scattering, and first-principles calculations for the electronic structure, we demonstrate the dependence of probability amplitude for single- and multiplasmon excitations on the basic parameters characterizing the photon pulse and the system. The resulting multiexcitation spectrum evolves towards a truncated plasmonic coherent state. Analogous concept is extrapolated to interpret plasmon generation by multiphoton excited electronic polarization. Based on this we elaborate a scenario that the thus created real plasmons act as supplementary frequency-locked pump field for non-Einsteinian plasmonically assisted channels of photoemission from metals. The established paradigm enables assignment and assessment of the observed linear $\hbarω_p$- and nonlinear $2\hbarω_p$-electron yields from Ag. Such effects may be exploited for selective filtering of optical energy conversion in electronic systems.
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