Does the unit cell size affect the wave function of graphene?

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SUMMARY

The wave function of graphene is influenced by its unit cell size, which consists of two carbon atoms (A and B). In the tight binding approximation, the wave function has two components corresponding to the p_z orbitals of each carbon atom. For each k value, the Bloch states are linear combinations of these two orbitals, leading to a number of Bloch states equal to the number of basis functions. Including additional orbitals such as p_x, p_y, and s will create more bands, but these are typically unoccupied and do not significantly affect the electronic properties of graphene.

PREREQUISITES
  • Tight binding approximation
  • Bloch states in solid-state physics
  • Orbital hybridization in carbon atoms
  • Graphene's electronic band structure
NEXT STEPS
  • Study the tight binding model for different materials
  • Explore the concept of Bloch's theorem in solid-state physics
  • Investigate the role of p_x and p_y orbitals in electronic properties
  • Learn about the band structure calculations using density functional theory (DFT)
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This discussion is beneficial for theoretical physicists, materials scientists, and anyone studying the electronic properties of graphene and other two-dimensional materials.

Newstein
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I have read many papers stating that the wave function of graphene has two components due to the fact that the unit cell of graphene consists of two carbon atoms (A and B atoms). However, I was confused about that. If the unit cell consist of more atoms, what will the wave function be? Does it has more component?
Do not deride me for my stupied question for I'm not majored in theory. Expecting someone's instruction.
 
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The point is more that there are two basis functions (a p_z orbital on each carbon atom) in the tight binding approximation. For each k value, the Bloch states are linear combinations of these two orbitals, or, to be more precise, they are obtained by a unitary transformation from these two orbitals. Hence there will be as many Bloch states as there are basis functions. Inclusion of the p_x, p_y and s orbitals will lead to the appearance of more bands which are however either completely occupied or unoccupied and lie below or above the pi orbitals. Hence they are of little interest as far as the electronic properties are concerned (however they are important to explain e.g. the bond strength in graphene).
 

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