Is zigzag graphene nanoribbon metallic or semiconducting?

[simsCity]

Hi,

* There is no bandgap for zigzag GNRs if the spin is neglected. In some of the studies in the literature, spin is neglected and analyses are done considering zigzag GNRs as metallic.

* In another group of works however, it is argued that spin-polarized bandstructure of zGNRs have small direct bandgap when they consider the spin-resolved calculations.

* Moreover in some studies such as

http://www.researchgate.net/publication/224541474_Magnetic_states_of_zigzag_graphene_nanoribbons_from_first_principles/file/d912f507c01965b8e4.pdf

say that antiferromagnetic spin state (AFM) is the ground state of zGNRs and ferromagnetic state (FM) has a bit higher energy. And they continue their analyses using spin-resolved calculations with AFM.

Hence, do I have to use AFM spin-resolved state in calculations as it is said to be the ground state? Then are the studies considering zGNRs as metallic fail?


Thanks in advance...

 

[TeethWhitener]

Neglecting spin, zigzag GNRs have no band gap. However, there is a (very) small spin orbit coupling which gives the material a band gap on the order of tens of meV, if I recall correctly.