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2025-05-26 18:19:05 +08:00
parent 8f0a6d32ef
commit 7d9a7723a6
3 changed files with 8 additions and 19 deletions

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@@ -41,12 +41,12 @@ We propose a method to estimate the magnitudes of the Raman tensors of these pho
This approach is founded on the assumption that the change in polarizability induced by atomic displacements in 4H-SiC
is primarily determined by the first- and second-nearest neighbors of the atom and the sign of the atomic charge,
while other factors (mass, bond length, etc.) only have small contributions.
As a result,
the phonon modes with the strongest Raman intensities can be predicted
prior to first-principles calculations and experiments (appendix),
and the Raman tensors of the calculated phonon modes can be estimated
before additional first-principles computations.
Further details are provided in the appendix.
Consequently, the Raman tensors of the calculated phonon modes can be estimated
before additional first-principles computations (see appendix for details),
and the results are summarized in @table-nopol.
The parameters $a_i$ exhibit significantly larger absolute values compared to $epsilon_i$, $eta_i$, and $zeta_i$,
indicating the E#sub[2] mode at 756.25 cm#super[-1] in simulation (mode 8)
possess a much higher Raman intensity than the others.
The Raman tensors and frequencies of the negligible-polar phonons were calculated using first-principles methods,
and the results are compared with both experimental data and theoretical predictions (@table-nopol).
@@ -78,24 +78,13 @@ The peek at 796 and 980 are caused by strong-polar phonons which will be discuss
Besides, there are small peeks at xxx,
which could not be explained in perfect 4H-SiC and will be discussed in the next section.
The method only takes the vibration directions of each atom in each phonon mode,
leaving the amplitudes unconsidered (see appendix for details),
and the result was summarized in @table-predmode.
In the Raman tensors in @table-predmode,
$a_i$ corresponding to the change of polarizability caused by movement of the Si atoms in A and C layers,
$epsilon_i$, $eta_i$ and $eta_i$ corresponding to the difference between different bilayers and different atoms.
Due to the similarity of environment in different bilayers and around different atoms,
the absolute values of $epsilon_i$, $eta_i$ and $zeta_i$ are expected to be much smaller than that of $a_i$,
thus the Raman tensors containing $a_i$ are expected to be much larger than those not containing $a_i$.
// TODO: 将一部分 phonons 改为 phonon modes
// 在论文中我们这样来称呼phonon 对应某一个特征向量,而 modes 对应于一个子空间。
// 也就是说,简并的里面有两个或者无数个 phonon但只有一个 mode
#include "table-nopol.typ"
#include "raman.typ"
#include "figure-raman.typ"
// 实验与计算基本相符。对于声子频率,计算总是低估大约 3%。
// 此外,一些较强的模式在预测无法看到的偏振中也可以看到。例如,一些在 xy 偏振中不应该看到的模式可以被看到了。

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@@ -63,5 +63,5 @@
// E2 E2 E1 2B1 A1 E1 E2 E2 A1 2B1
m2[*Polarity*], m(4)[None], m2[Weak], m2[None], m(4)[Weak], m(4)[None], m2[Weak], m2[None],
)},
caption: [Negaligible-polarized Phonons at $Gamma$ Point],
caption: [Negaligible-polarized Phonons at $Gamma$ Point.],
)<table-nopol>]