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Abstract The surface magnetization of Fe3GeTe2was examined by low-energy electron microscopy (LEEM) using an off-normal incidence electron beam. We found that the 180° domain walls are of Bloch type. Temperature-dependent LEEM measurements yield a surface magnetization with a surface critical exponentβ1 = 0.79 ± 0.02. This result is consistent with surface magnetism in the 3D semi-infinite Heisenberg (β1 = 0.84 ± 0.01) or Ising (β1 = 0.78 ± 0.02) models, which is distinctly different from the bulk exponent (β= 0.34 ± 0.07). The measurements reveal the power of LEEM with a tilted beam to determine magnetic domain structure in quantum materials without the need for the use of spin-polarized electrons. Single crystal diffraction measurements reveal inversion symmetry-breaking weak peaks and yield space group P-6m2. This Fe site defect-derived loss of inversion symmetry enables the formation of skyrmions in this Fe3GeTe2crystal.
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Directing valley-polarized emission of 3 L WS 2 by photonic crystal with directional circular dichroism
The valley degree of freedom that results from broken inversion symmetry in two-dimensional (2D) transition-metal dichalcogenides (TMDCs) has sparked a lot of interest due to its huge potential in information processing. In this experimental work, to optically address the valley-polarized emission from three-layer (3 L) thick WS2at room temperature, we employ a SiN photonic crystal slab that has two sets of holes in a square lattice that supports directional circular dichroism engendered by delocalized guided mode resonances. By perturbatively breaking the inversion symmetry of the photonic crystal slab, we can simultaneously manipulate s and p components of the radiating field so that these resonances correspond to circularly polarized emission. The emission of excitons from distinct valleys is coupled into different radiative channels and hence separated in the farfield. This directional exciton emission from selective valleys provides a potential route for valley-polarized light emitters, which lays the groundwork for future valleytronic devices.
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- Award ID(s):
- 2139416
- PAR ID:
- 10489714
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Express
- Volume:
- 32
- Issue:
- 4
- ISSN:
- 1094-4087; OPEXFF
- Format(s):
- Medium: X Size: Article No. 6076
- Size(s):
- Article No. 6076
- Sponsoring Org:
- National Science Foundation
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