| Description |
When a Dirac semimetal is subject to a circularly polarized laser, it is
predicted that the Dirac cone splits into two Weyl nodes and a non-equilibrium
transient state called the Floquet Weyl semimetal is realized. We focus on the
previously unexplored low frequency regime, where the upper and lower Dirac
bands resonantly couples with each other through multi-photon processes, which
is a realistic situation in solid state ultrafast pump-probe experiments. We
find a series of new Weyl nodes emerging in pairs when the Floquet replica bands
hybridize with each other. The nature of the Floquet Weyl semimetal with regard
to the number, locations, and monopole charges of these Weyl nodes is highly
tunable with the amplitude and frequency of the light. We derive an effective
low energy theory using Brillouin-Wigner expansion and further regularise the
theory on a cubic lattice. The monopole charges obtained from the low-energy
Hamiltonian can be reconciled with the number of Fermi arcs on the lattice which
we find numerically.
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