Band mapping in higher-energy x-ray photoemission: Phonon effects and comparison to one-step theory
Band mapping in higher-energy x-ray photoemission: Phonon effects and comparison to one-step theory
复制标题
高能 X 射线光电发射中的能带映射：声子效应以及与一步理论的比较
DOI：
10.1103/physrevb.78.035108
复制
发表时间：
2008
影响因子：
3.7
通讯作者：
C. Fadley
中科院分区：
文献类型：
--
作者：
L. Plucinski;J. Minár;B. Sell;J. Braun;H. Ebert;C. Schneider;C. Fadley
We have studied the temperature dependence of W(110) soft x-ray angle-resolved photoemission spectra excited at photon energies of 260 and 870 eV and between 300 and 780 K. The experimental results have been compared to both a free-electron final-state model and theoretical one-step model calculations of the photocurrent. At 300 K, clear band dispersions can be observed in the data. The temperature dependence of the data can be analyzed qualitatively in terms of a direct-transition band-dispersion regime (``UPS'' limit) versus a nondirect-transition density-of-states regime (``XPS'' limit). The ratio between direct and nondirect transitions is estimated from a Debye-Waller factor, which for example at $h\ensuremath{\nu}=870\text{ }\text{eV}$ predicts 70% direct transitions at 300 K, and 41% at 780 K, and these values qualitatively describe our data. Beyond this, the state-of-the-art one-step theoretical calculations reproduce well the band dispersions and matrix element effects in the measured spectra at room temperature. However, simulating the temperature dependence is more complicated, and including phonon effects via complex phase shifts accounts for the suppression of existing direct-transition features, but does not reproduce new, density-of-states-related background intensity which shows up in higher-temperature experimental spectra. Finally, we also discuss the implications of this work for future experiments on other materials and at even higher photon energies up to 10 keV.
