181 research outputs found
Laser induced surface magnetization in Floquet-Weyl semimetals
We investigate optically induced magnetization in Floquet-Weyl semimetals
generated by irradiation of a circularly-polarized continuous-wave laser from
the group II-V narrow gap semiconductor ZnAs in a theoretical manner.
Here, this trivial and nonmagnetic crystal is driven by the laser with a nearly
resonant frequency with a band gap to generate two types of Floquet-Weyl
semimetal phases composed of different spin states. These two phases host
nontrivial two-dimensional surface states pinned to the respective pairs of the
Weyl points. By numerically evaluating the laser-induced transient
carrier-dynamics, it is found that both spins are distributed in an uneven
manner on the corresponding surface states, respectively, due to significantly
different excitation probabilities caused by the circularly-polarized laser
with the nearly resonant frequency. It is likely that such spin-polarized
surface states produce surface magnetization, and furthermore the inverse
Faraday effect also contributes almost as much as the spin magnetization. To be
more specific, excited carries with high density of the order of are generated by the laser with electric field strength of a few
MV/cm to result in the surface magnetization that becomes asymptotically
constant with respect to time, around 1 mT. The magnitude and the direction of
it depend sharply on both of the intensity and frequency of the driving laser,
which would be detected by virtue of the magneto-optic Kerr effect.Comment: 18 pages, 7 figure
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