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  • Why is the in-plane dielectric constant of transition metal dichalcogenides larger than the out-of-plane dielectric constant? Is this because of the spacing between monolayers of the TMD?
  • Why do these dielectric constants depend on the thickness and increase with increasing thickness?
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The dielectric constant, or more appropriately, the dielectric function, can be thought of as a measure of screening. A simple relation for which to picture this is:

$V_{eff} = V_{ext}/\epsilon$

Therefore, in TMDs, since the electrons are more mobile in the planes, they tend to screen potentials with a greater efficiency. This gives a higher dielectric constant.

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  • $\begingroup$ If it is about screening, why it changes with thickness? $\endgroup$
    – Roy
    Mar 26, 2015 at 6:54
  • $\begingroup$ One would expect that the screening would change due to the presence of other layers. I think that this should be intuitively plausible. $\endgroup$
    – Xcheckr
    Mar 26, 2015 at 12:48

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