Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Half-metallic graphene nanodots   A comprehensive first-principles theoretical study of the electronic
properties and half-metallic nature of finite rectangular graphene nanoribbons
is presented. We identify the bisanthrene isomer of the C28H14 molecule to be
the smallest polycyclic aromatic hydrocarbon to present a spin polarized ground
state. Even at this quantum dot level, the spins are predicted to be aligned
antiferromagnetically at the two zigzag edges of the molecule. As a rule of
thumb, we find that zigzag edges that are at least three consecutive units
long, will present spin polarization if the width of the system is 1 nm or
wider. Room temperature detectability of the magnetic ordering is predicted for
molecules with zigzag edges 1 nm and longer. For the longer systems studied,
spin wave structures appear in some high spin multiplicity states. Energy gap
oscillations with the length of the zigzag edge are observed. The amplitude of
these oscillations is found to be smaller than that predicted for infinite
ribbons. The half-metallic nature of the ribbons under an external in-plane
electric field is found to be preserved even for finite and extremely short
systems.

26
The categories of this paper are: bayes-an
36
The categories of this paper are: cmp-lg
17
The categories of this paper are: q-fin
6
The categories of this paper are: astro-ph
3
The categories of this paper are: physics
25
The categories of this paper are: patt-sol
20
The categories of this paper are: acc-phys
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
29
The categories of this paper are: funct-an
5
The categories of this paper are: gr-qc
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th