Detection of electron paramagnetic resonance spectra of optically induced carriers with the properties of the effective mass in the WS$_2$ transition metal dichalcogenide

The spin properties of transition metal dichalcogenides are of interest for applications in spintronics. Anisotropic electron paramagnetic resonance spectra in a WS$_2$ single crystal under optical excitation have been detected. These spectra assumingly belong to localized carriers near the valence band and reflect features of the $5d$ shell of the crystal. It has been shown that the $g$-factor for the magnetic field perpendicular to the $c$-axis of the crystal (in-plane magnetic field) is larger than that for the magnetic field parallel to the $c$-axis (perpendicular to the layer plane), which can provide information on the type of the $5d$-function. The discussed center is most likely described by the $5d(z^2-r^2)$ wavefunction, which can be associated with the valence band of the crystal.