Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Second-order magnetic responses in quantum magnets: Magnetization under
  ac magnetic fields   We investigate second-order magnetic responses of quantum magnets against ac
magnetic fields. We focus on the case where the $z$ component of the spin is
conserved in the unperturbed Hamiltonian and the driving field is applied in
the $xy$ plane. We find that linearly polarized driving fields induce a
second-harmonic response, while circularly polarized fields generate only a
zero frequency response, leading to a magnetization with a direction determined
by the helicity. Employing an unbiased numerical method, we demonstrate the
nonlinear magnetic effect driven by the circularly polarized field in the XXZ
model and show that the magnitude of the magnetization can be predicted by the
dynamical spin structure factor in the linear response regime.

21
The categories of this paper are: adap-org
30
The categories of this paper are: q-alg
11
The categories of this paper are: hep-lat
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
35
The categories of this paper are: mtrl-th
25
The categories of this paper are: patt-sol
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph
7
The categories of this paper are: hep-th
10
The categories of this paper are: q-bio
20
The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
8
The categories of this paper are: hep-ex