金属玻璃剪切带中的等离子体激元能量损失
Plasmon energy losses in shear bands of metallic glass
摘要：
观察到冷轧Al $_{88}$ Y $_{7}$ Fe $_{5}$金属玻璃中塑性形变产生的剪切带沿其传播方向呈现交替的密度变化。电子能量损失谱（EELS）被用来研究剪切带内和周围的体积等离子体能量损失。使用开源Python模块（Hyperspy）以洛伦兹函数拟合等离子体激元和零损耗峰的形状，在几meV的精度内精确确定了峰中心的能量偏移和反映阻尼的峰宽（FWHM）变化。最大体等离子体激元能量位移计算为明亮和黑暗的剪切带段相对于矩阵为约38和14毫电子伏，分别。阻尼被观察到是更大的密集的区域。这里提出的分析表明，在等离子体激元的变化是由两个贡献：（i）由于在中程序（MRO）的变化在剪切带段的可变阻尼。这会影响静态结构系数S（k），进而根据Ziman-Baym公式导致阻尼减小或增大。(ii)出现在零动量等离子体频率公式$E_p(q=0)$中的离子密度和有效电子质量是耦合的，并且引起等离子体能量的微小变化。该模型预测的等离子体激元能量转移的顺序meV。
英文摘要：
Shear bands resulting from plastic deformation in cold-rolled Al$_{88}$Y$_{7}$Fe$_{5}$ metallic glass were observed to display alternating density changes along their propagation direction. Electron-energy loss spectroscopy (EELS) was used to investigate the volume plasmon energy losses in and around shear bands. Energy shifts of the peak centre and changes in the peak width (FWHM) reflecting the damping were precisely determined within an accuracy of a few meV using an open source python module (Hyperspy) to fit the shapes of the plasmon and zero-loss peaks with Lorentzian functions. The maximum bulk plasmon energy shifts were calculated for the bright and dark shear band segments relative to the matrix to be about 38 and 14 meV, respectively. The damping was observed to be larger for the denser regions. The analysis presented here suggests that the changes in the plasmons are caused by two contributions: (i) Variable damping in the shear band segments due to changes in the medium-range order (MRO). This affects the static structure factor S(k), which, in turn, leads to either reduced or increased damping according to the Ziman-Baym formula. (ii) The ionic density and the effective electron mass appearing in the zero-momentum plasmon frequency formula $E_p(q=0)$ are coupled and give rise to small variations in the plasmon energy. The model predicts plasmon energy shifts in the order of meV.
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