Z2 invariant for 2D material (or a semi-infinite slab)

[koushik pal]

Hello All,

I was wondering if it's possible to calculate Z2 invariant
for a 2D material (or a semi-infinite slab) using the Z2Pack code.

Let's say I have  a slab model with (001) surface orientation
(i.e. vacuum is along the z-direction of the slab). To determine
the topological invariant of  this (001) slab,  shall I calculate the
Z_2 invariant for kz=0 and kz=0.5 planes, and take their difference
modulo 2?

The problem here is the following.  As this is a slab, kz=0.5 plane
does not have any physical meaning. So I don't know if Z2 invariant
on kz=0.5 plane has some significance.
Please correct me if I am missing something here, and suggest me
ways to calculate Z2 invariant for such a slab.

Thanks in advance.

Best regards,
Koushik

Graduate student
JNCASR
Bangalore, India
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