Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Laser-induced terahertz spin transport in magnetic nanostructures arises
  from the same force as ultrafast demagnetization   Laser-induced terahertz spin transport (TST) and ultrafast demagnetization
(UDM) are central but so far disconnected phenomena in femtomagnetism and
terahertz spintronics. Here, we use broadband terahertz emission spectroscopy
to reliably measure both processes in one setup. We find that the rate of UDM
of a single ferromagnetic metal film F has the same time evolution as the flux
of TST from F into an adjacent normal-metal layer N. This remarkable agreement
shows that UDM and TST are driven by the same force, which is fully determined
by the state of the ferromagnet. An analytical model consistently and
quantitatively explains our observations. It reveals that both UDM in F and TST
in the F|N stack arise from a generalized spin voltage, which is defined for
arbitrary, nonthermal electron distributions. We also conclude that
contributions due to a possible temperature difference between F and N are
minor and that the spin-current amplitude can, in principle, be increased by
one order of magnitude. In general, our findings allow one to apply the vast
knowledge of UDM to TST, thereby opening up new pathways toward large-amplitude
terahertz spin currents and, thus, energy-efficient ultrafast spintronic
devices.

22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph
28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
17
The categories of this paper are: q-fin
27
The categories of this paper are: comp-gas
15
The categories of this paper are: nucl-ex
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
32
The categories of this paper are: atom-ph
11
The categories of this paper are: hep-lat
29
The categories of this paper are: funct-an
9
The categories of this paper are: nlin