# Explanation of the Diagram of the Rashba Effect

## Main Question or Discussion Point

Hello,

I find something about the Rashba Spin Orbit coupling but im not sure how to understand it. Hope you can help me. Consider the following picture of the Rashba effect i found:

Well i dont really know whats about the arrows here. They should showing the spin direction i guess but i dont see there meaning.
Can somebody help how to interprete this diagram??

## Answers and Replies

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TeethWhitener
Gold Member
The $k_x$ vs. $k_y$ plot is just a slice through the $E(\mathbf{k})$ vs. $\mathbf{k}$ plot at constant $|\mathbf{k}|$. Basically, imagine rotating the right-hand diagram about the $E(k)$ axis and slicing through $E = 0$. The arrows simply show that the spins become momentum-dependent. The inner ring has opposite spins from the outer ring, but the spin projections are going to depend on where along those rings you are in momentum space.

At the risk of casting more confusion on the topic, I found this picture, https://www.physics.harvard.edu/node/549, which seems to contradict your picture. Harvard's picture make more sense to me:-)

TeethWhitener