75 research outputs found
Tunable Intrinsic Plasmons due to Band Inversion in Topological Materials
The band inversion has led to rich physical effects in both topological
insulators and topological semimetals. It has been found that the inverted band
structure with the Mexican-hat dispersion could enhance the interband
correlation leading to a strong intrinsic plasmon excitation. Its frequency
ranges from several to tens of and can be
effectively tuned by the external fields. The electron-hole asymmetric term
splits the peak of the plasmon excitation into double peaks. The fate and
properties of this plasmon excitation can also act as a probe to characterize
the topological phases even in the lightly doped systems. We numerically
demonstrate the impact of the band inversion on plasmon excitations in
magnetically doped thin films of three-dimensional strong topological
insulators, V- or Cr-doped (Bi, Sb)Te, which support the quantum
anomalous Hall states. Our work thus sheds some new light on the potential
applications of topological materials in plasmonics.Comment: 6 pages, 5 figures, Accepted in PR
Large magneto-optical Kerr effect in noncollinear antiferromagnets Mn ( = Rh, Ir, or Pt)
Magneto-optical Kerr effect, normally found in magnetic materials with
nonzero magnetization such as ferromagnets and ferrimagnets, has been known for
more than a century. Here, using first-principles density functional theory, we
demonstrate large magneto-optical Kerr effect in high temperature noncollinear
antiferromagnets Mn ( = Rh, Ir, or Pt), in contrast to usual wisdom.
The calculated Kerr rotation angles are large, being comparable to that of
transition metal magnets such as bcc Fe. The large Kerr rotation angles and
ellipticities are found to originate from the lifting of the band
double-degeneracy due to the absence of spatial symmetry in the Mn
noncollinear antiferromagnets which together with the time-reversal symmetry
would preserve the Kramers theorem. Our results indicate that Mn would
provide a rare material platform for exploration of subtle magneto-optical
phenomena in noncollinear magnetic materials without net magnetization
Intrinsic spin Hall effect in monolayers of group-VI dichalcogenides: A first-principles study
Using first-principles calculations within density functional theory, we
investigate the intrinsic spin Hall effect in monolayers of group-VI
transition-metal dichalcogenides MX2 (M = Mo, W and X = S, Se). MX2 monolayers
are direct band-gap semiconductors with two degenerate valleys located at the
corners of the hexagonal Brillouin zone. Because of the inversion symmetry
breaking and the strong spin-orbit coupling, charge carriers in opposite
valleys carry opposite Berry curvature and spin moment, giving rise to both a
valley- and a spin-Hall effect. The intrinsic spin Hall conductivity (ISHC) in
p-doped samples is found to be much larger than the ISHC in n-doped samples due
to the large spin-splitting at the valence band maximum. We also show that the
ISHC in inversion-symmetric bulk dichalcogenides is an order of magnitude
smaller compared to monolayers. Our result demonstrates monolayer
dichalcogenides as an ideal platform for the integration of valleytronics and
spintronics.Comment: published version (7 pages, 6 figures
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