  Magneto-electronic properties of buckled monolayer GaAs is studied by the
developed generalized tight-binding model, considering the buckled structure,
multi-orbital chemical bondings, spin-orbit coupling, electric field, and
magnetic field simultaneously. Three group of spin-polarized Landau levels
(LLs) near the Fermi level are induced by the magnetic quantization, whose
initial energies, LL degeneracy, energy spacings, magnetic-field-dependence,
and spin polarization are investigated. The Landau state probabilities
describing the oscillation patterns, localization centers, and node
regularities of the dominated/minor orbitals are analyzed, and their
energy-dependent variations are discussed. The given density of states directly
reflects the main features of the LL energy spectra in the structure, height,
number, and frequency of the spin-polarized LL peaks. The electric field causes
the monotonous/nonmonotonous LL energy dispersions, LL crossing, gap
modulation, phase transition and spin splitting enhancement. The complex gap
modulations and phase transitions based on the competition between magnetic and
electric fields are explored in detail by the phase diagram. The
field-controlled gap modulations and phase transitions are helpful in designing
the top-gated and phase-change electronic devices. These predicted
magneto-electronic properties could be verified by scanning tunneling
spectroscopy measurements.
