Electron and hole fermi surface-what does it mean?

[lavster]

hi i was reading the following paragraph and i do not understand what it means. can someone explain what it means to me please? i know what the individual concepts are eg fermi line, hall coefficeint extended zone schemes, but am not grasping the concept of the two types of fermi surface...


"For electron states contained within the fermi line in reduced or periodically extended zone schemes we have an electron fermi surface and a negative hall coefficient. For electron states contained outside the Fermi line in reduced or periodically extended zone schemes we have a hole fermi surface and a positive hall coefficient."


thanks

 

[BigJDubs]

!This paragraph is talking about the Fermi surface, which is a surface in momentum space that separates the states that are occupied by electrons from the states that are unoccupied. The Fermi line is the line in momentum space that marks the boundary between the occupied and unoccupied states. If the electron states are contained within the Fermi line, then this means that the electrons are occupying all of the states below the Fermi line in momentum space. This is known as an electron Fermi surface, and it has a negative Hall coefficient. If the electron states are contained outside of the Fermi line, then this means that the electrons are occupying all of the states above the Fermi line in momentum space. This is known as a hole Fermi surface, and it has a positive Hall coefficient.