Feedback from Past Papers

Question 1

Use the Einstein relation to explain why electrons near Dirac points can be seen as massless.

Answer 1

Einstein: E = pc = ħkc
Dirac: E = ħkv
so Fermi electrons at Dirac points behave as massless photons with Fermi v instead of c.

Question 2

Condition for Conductivity in zig-zag CNT.

Answer 2

n/3 = integer

Question 3

State the spectroscopy modes and what they can be used to determine.

Answer 3

I vs z -> avg tip-sample work function
I vs V (bias voltage) -> local density of states