19 lines
1.1 KiB
XML
19 lines
1.1 KiB
XML
== Symmetry Analysis of Phonons in 4H-SiC
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The phonons at the #sym.Gamma point in 4H-SiC (space group P6#sub[3]mc)
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corresponds to four irreducible representations of C#sub[6v] point group
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(4A#sub[1] + 4B#sub[1] + 4E#sub[1] + 4E#sub[2]),
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including translational movement (1A#sub[1] + 1E#sub[1]), strong polar modes (1A#sub[1] + 1E#sub[1]),
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and negligible-polar modes (2A#sub[1] + 4B#sub[1] + 2E#sub[1] + 4E#sub[2]).
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// The form of the Raman tensors for each representation is well known and summarized in @table-rep.
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// #include "table-rep.typ"
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By further decomposing the doubly degenerate modes (E#sub[1] and E#sub[2] of C#sub[6v] group)
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into the C#sub[2v] point group,
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the raman scattering corresponding to vibration along x and y directions could be distinguished.
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For example, the E#sub[2] peeks observed in the Raman experiment of z(yy)#overline[z]
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correspond to phonons vibrating along the y direction,
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while the E#sub[2] peeks observed in z(yx)#overline[z] correspond to phonons vibrating along the x direction.
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This is important when the x and y directions become inequivalent and the double degeneracies are slightly lifted.
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