Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Inducing and controlling rotation on small objects using photonic
  topological materials   Photonic topological insulator plates violate Lorentz reciprocity which leads
to a directionality of surface-guided modes. This in-plane directionality can
be imprinted via an applied magnetic field. On the basis of macroscopic quantum
electrodynamics in nonreciprocal media, we show that two photonic topological
insulator surfaces are subject to a tuneable, magnetic-field dependent Casimir
torque. Due to the directionality, this torque exhibits a unique $2\pi$
periodicity, in contradistinction to the Casimir torques encountered for
reciprocal uniaxial birefringent media or corrugated surfaces which are
$\pi$-periodic. Remarkably, the torque direction and strength can be externally
driven in situ by simply applying a magnetic field on the system, and we show
that this can be exploited to induce a control the rotation of small objects.
Our predictions can be relevant for nano-opto-mechanical experiments and
devices.

15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin
34
The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys
25
The categories of this paper are: patt-sol
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
21
The categories of this paper are: adap-org
29
The categories of this paper are: funct-an
26
The categories of this paper are: bayes-an
10
The categories of this paper are: q-bio
2
The categories of this paper are: math
22
The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
7
The categories of this paper are: hep-th