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Jun20-09, 02:36 PM
P: 32
Thank you for the answer

very interesting this "valley isotropic" representation...

what you say gives me a little suggestion that what I previously intended for "helicity" is relabled by these authors with the term "chirality", which term I used to call something else (what I used to call chirality here becomes simply the valley index if I understood well, I mean the one distinguishing the two dirac points)....

can you tell me something that could help me clarify better the situation?... in this preprint

you see picture two part 1 at page 4... I wanted to ask you is this picture is referred to states around the K point... and if it is correct that, considering also electrons in K' point I should reverse the direction of all the pseudospin vectors ...

if it is this way, I wonder: why doesn't the book specify that? Is it because processes between the two valleys do not happen and so I can fix one valley and work only with that? Furthermore, pseudospin is always conserved if two valleys interact?