Generally we say that the density of states (DOS) at Fermi level contribute to many phenomenon. However in the Dirac cone DOS is zero at Fermi level. What does it mean and what are its consequences? Why it is important in topological insulators to have Dirac point at the Fermi level. is it not good if Dirac point is in the gap of bulk band structure instead of Fermi level?
Dear Vk Singh,
The main consequence of having only one point in the Fermi level is that they are semimetals, i.e. with very bad electronic and thermal conductivities. But they can be easily transformed in semiconductors. Notice that besides the new topological materials there are other semimetals as Si or Ge very important for the technology because they can act as semiconductors. The As, Te or Sb are semimetals which play a fundamental role in the topological insulators, therefore this property of their electronic bands is a very important feature for explaining their transport properties.
See [1], in particular Sec. 6.4, p. 184, herein.
[1] H Aoki, and MS Dresselhaus, Editors, Physics of Graphene (Springer, Heidelberg, 2014).
It can be a positive or negative. In case of standing alone graphene, there are no density of states at Ef = 0, which leads to a zero transmission coefficient and high resistance. However, this low density of states can be beneficial when when bringing graphene with other materials, i. e. hybrid structures. As the conductance can be enhanced.
Vk Singh
this is due to the erroneous proof of fermi energy level by Dirac, with correct mathematics on the chemical potential fermi level is no more a straight line instead it is a oblique line connecting VB to CB. and this line is the line of transition, so any point chosen on this have meaning...later more on this.
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