Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Semiclassical conservation of spin and large transverse spin current in
  Dirac systems   In Dirac materials, the low energy excitations obey the relativistic Dirac
equation. This dependence implies that the electrons are exposed to strong
spin-orbit coupling. Hence, real spin conservation is believed to be violated
in Dirac materials. We show that this point of view needs to be refined in the
semiclassical picture which applies to the case of doped Dirac materials (away
from the nodal point in the spectrum). We derive a novel type of Boltzmann
equation for these systems if they are brought slightly out-of-equilibrium.
Remarkably, spin-momentum locking is softened and a generalized spin
conservation law can be formulated. The most striking observable consequence of
our theory is a large transverse spin current in a nearly ballistic transport
regime.

9
The categories of this paper are: nlin
11
The categories of this paper are: hep-lat
3
The categories of this paper are: physics
5
The categories of this paper are: gr-qc
22
The categories of this paper are: chao-dyn
32
The categories of this paper are: atom-ph
0
The categories of this paper are: hep-ph
34
The categories of this paper are: chem-ph
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
24
The categories of this paper are: dg-ga
6
The categories of this paper are: astro-ph
19
The categories of this paper are: eess
31
The categories of this paper are: ao-sci
17
The categories of this paper are: q-fin