43 lines
2.7 KiB
XML
43 lines
2.7 KiB
XML
== Phonons in Perfect 4H-SiC
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不同方向入射光的声子位置不同。
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声子的性质与它们在倒空间中的位置（即波矢）有关，而参与拉曼散射的声子波矢则由激光波长和拉曼入射配置（正入射、掠入射、边入射）决定。
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在我们的实验（绿光）中，参与拉曼散射的声子都位于 Gamma 点附近（距离仅 xxx 埃），而与 Gamma 点的相对方向则根据入射配置而定。
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对于正入射，声子大致位于 Gamma-A 线上；对于边入射，声子大致位于 Gamma-K 线上。对于掠入射，声子不位于任何高对称线上。
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The properties of phonons depend on their positions in reciprocal space (i.e., their wavevectors),
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and the wavevectors of phonons participating in a Raman scattering process
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are determined by the Raman experiment configuration.
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In our experiments (back-scattering with 532 nm laser light),
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the phonons involved are located very close to the #sym.Gamma point (approximately $5.13 times 10^(-3) angstrom$),
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and direction relative to the #sym.Gamma point is determined by the incidence configurations.
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For normal and edge incidence,
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the relevant phonons lie approximately along the #sym.Gamma–A and #sym.Gamma–K lines, respectively,
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as illustrated in @figure-discont.
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For grazing incidence,
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the relevant phonons do not reside on any high-symmetry lines and are therefore not depicted in the figure.
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#include "figure-discont.typ"
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每个点都有 21 个声子模式。我们把它分成 18 个极性很小的和 3 个极性很强的两类。
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对于每一个 Gamma 附近的点，都有 21 个声子模式（简并模式按简并数计）。
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我们将这 21 个声子模式分为两类：18 个极性可以忽略的声子模式（即极性为零或非常弱的声子），在拉曼散射过程中它们的电极性造成的效应可以忽略；
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和 3 个强极性声子模式，在拉曼光谱中电极性效应是可观测的。
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At each such position near the #sym.Gamma point,
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there exist 21 phonon modes (with degeneracies counted accordingly).
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These modes were categorized into two groups according to their electrical polarities:
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18 negligible-polar phonons (i.e., zero or very weak electrical polarity),
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in which same species atoms vibrate in opposite directions and the electrical cancellated with each other,
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leading to negligible electrical polarity during Raman scattering process,
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shown as gray lines in @figure-discont;
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and three strong-polar phonons,
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in which all atoms of the same species vibrate in the same direction,
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resulting in a strong dipole moment and observable electrical polarity in Raman spectra,
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shown as colored lines in @figure-discont.
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#include "non-polar/default.typ"
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#include "polar/default.typ"
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