9 research outputs found
Magnon gap excitations and spin-entangled optical transition in van der Waals antiferromagnet NiPS3
Optical magneto-spectroscopy methods (Raman scattering, far-infrared
transmission, and photoluminescence) have been applied to investigate the
properties of the NiPS3 semiconducting antiferromagnet. The fundamental magnon
gap excitation in this van der Waals material has been found to be split into
two components, in support of the biaxial character of the NiPS3
antiferromagnet. Photoluminescence measurements in the near-infrared spectral
range show that the intriguing 1.475 eV-excitation unique to the NiPS3
antiferromagnetic phase splits upon the application of the in-plane magnetic
field. The observed splitting patterns are correlated with properties of magnon
excitations and reproduced with the simple model proposed. Possible routes
toward a firm identification of the spin-entangled 1.475 eV-optical excitation
in NiPS3, which can hardly be recognized as a coherent Zhang-Rice exciton, are
discussed.Comment: 8 pages, 8 figure
Exchange gap in GdPtBi probed by magneto-optics
We measured the magneto-reflectivity spectra (4 - 90 meV, 0 - 16 T) of the
triple-point semimetal GdPtBi and found them to demonstrate two unusual broad
features emerging in field. The electronic bands of GdPtBi are expected to
experience large exchange-mediated shifts, which lends itself to a description
via effective Zeeman splittings with a large g factor. Based on this approach,
along with an ab initio band structure analysis, we propose a model Hamiltonian
that describes our observations well and allows us to estimate the effective g
factor, g* = 95. We conclude that we directly observe the exchange-induced
band inversion in GdPtBi by means of infrared spectroscopy.Comment: 9 pages, SM include
Magnon gap excitations in van der Waals antiferromagnet MnPSe
Magneto-spectroscopy methods have been employed to study the zero-wavevector
magnon excitations in MnPSe. Experiments carried out as a function of
temperature and the applied magnetic field show that two low-energy magnon
branches of MnPSe in its antiferromagnetic phase are gapped. The
observation of two low-energy magnon gaps (at 14 and 0.7 cm) implies
that MnPSe is a biaxial antiferromagnet. A relatively strong out-of-plane
anisotropy imposes the spin alignment to be in-plane whereas the spin
directionality within the plane is governed by a factor of 2.5
10 weaker in-plane anisotropy.Comment: 9 pages, 3 figure
Landau level spectroscopy of BiTe
Here we report on Landau level spectroscopy in magnetic fields up to 34 T
performed on a thin film of topological insulator BiTe epitaxially
grown on a BaF substrate. The observed response is consistent with the
picture of a direct-gap semiconductor in which charge carriers closely resemble
massive Dirac particles. The fundamental band gap reaches ~meV
at low temperatures and it is not located on the trigonal axis, thus displaying
either six or twelvefold valley degeneracy. Notably, our magneto-optical data
do not indicate any band inversion. This suggests that the fundamental band gap
is relatively distant from the point where profound inversion exists
andgives rise to relativistic-like surface states of BiTe.Comment: 12 pages, 11 figures, to be published in Phys. Rev.
Magnon gap excitations and spin-entangled optical transition in the van der Waals antiferromagnet NiPS 3
International audienceOptical magneto-spectroscopy methods (Raman scattering, far-infrared transmission, and photoluminescence) have been applied to investigate the properties of the NiPS 3 semiconducting antiferromagnet. The fundamental magnon gap excitation in this van der Waals material has been found to be split into two components, in support of the biaxial character of the NiPS 3 antiferromagnet. Photoluminescence measurements in the near-infrared spectral range show that the intriguing 1.475 eV excitation unique to the NiPS 3 antiferromagnetic phase splits upon the application of the in-plane magnetic field. The observed splitting patterns are correlated with properties of magnon excitations and reproduced with the simple model proposed. Possible routes towards a firm identification of the spin-entangled 1.475 eV optical excitation in NiPS 3 , which can hardly be recognized as a coherent Zhang-Rice exciton, are discussed
Temperature dependence of the energy band gap in ZrTe 5 : Implications for the topological phase
International audienceUsing Landau-level spectroscopy, we determine the temperature dependence of the energy band gap in zirconium pentatelluride (ZrTe 5). We find that the band gap reaches E g = (5 ± 1) meV at low temperatures and increases monotonically when the temperature is raised. This implies that ZrTe 5 is a weak topological insulator, with noninverted ordering of electronic bands in the center of the Brillouin zone. Our magnetotransport experiments performed in parallel show that the resistivity anomaly in ZrTe 5 is not connected with the temperature dependence of the band gap
Transverse and longitudinal magnons in the strongly anisotropic antiferromagnet FePSe 3
International audienc
Polaronic interaction in a single modulation-doped GaAs quantum well with the Feynman-Hellwarth-Iddings-Platzman approximation
International audienceAbsolute far-infrared magnetotransmission experiments have been performed in magnetic fields up to 33.5 T on a series of single GaAs quantum wells doped with different electron concentrations. The transmission spectra have been simulated with a multilayer dielectric model. The imaginary part of the optical response function, which reveals singular features related to the electron-phonon interactions, has been extracted. In addition to the expected polaronic effects due to the longitudinal-optical phonon of GaAs, additional interactions with interface phonons are observed. The main interaction is analyzed quantitatively with the Feynman-Hellwarth-Iddings-Platzman model, which is shown to predict correctly the concentration of carriers beyond which the Fröhlich interaction is completely screened
Evidence for three-dimensional Dirac conical bands in TlBiSSe by optical and magneto-optical spectroscopy
TlBiSSe is a rare realization of a three-dimensional semimetal with a conically dispersing band that has an optical response which is well isolated from other contributions in a broad range of photon energies. We report optical and magneto-optical spectroscopy on this material. When the compound is chemically tuned into a state of the lowest carrier concentration, we find a nearly linear frequency dependence of the optical conductivity below 0.5 eV. Landau level spectroscopy allows us to describe the system with a massive Dirac model, giving a gap 2Δ=32 meV and an in-plane velocity parameter vxy=4.0×105 m/s