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16 votes

How to understand the spin of exciton?

As you mentioned in the question, excitons are indeed bound electron-hole pairs. They are often considered to be the signature of optical spectra in insulating solids. Adding onto the comment by tmph, ...
  • 2,212
9 votes

How to understand the spin of exciton?

First I mention this very similar question on Physics SE and the related answer. Then, a couple of points which are not well addressed in the previous answer in my opinion. First of all we are here ...
9 votes
Accepted

Why can't we change the spin angular momentum of electrons with an external optical field?

This has already been asked in several forms in Physics Stack Exchange. Within the semi-classical 'electric dipole' approximation, only the electric field of light interacts with the electron. The ...
  • 2,212
7 votes

How to evaluate the exciton velocity?

Not a direct answer to your proposed approximation to the exciton group velocity as $\mathbf{Q}\to0$, but just wanted to point out that the latest version of Yambo supports the calculation of exciton ...
  • 10.4k
7 votes
Accepted

How can I find the binding energy for exciton (optical gap) with VASP?

The model you are describing corresponds to a Wannier-Mott exciton and the binding energy is approximated by: $$ \tag{1} E_{\mathrm{B}}=\frac{\mu}{\epsilon^2_{\infty}}R, $$ where $\mu$ is the reduced ...
  • 10.4k
6 votes

Why can't we change the spin angular momentum of electrons with an external optical field?

well, you certainly can change the spin of an electron through acting on its orbital motion with the electric field. It is called "spin-orbit coupling" (SOC) and a lot of magneto-optical and ...
  • 291
5 votes

Why can't we change the spin angular momentum of electrons with an external optical field?

I think the claim assumes linear polarization of the light which has zero angular momentum. For circularly polarized light, the spin of the electron should be flipped. (e.g. Appl. Phys. Lett. 114, ...

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