Magneto photoluminescence measurements of tungsten disulphide monolayers

Abstract

Layered transition-metal dichalcogenides have attracted great interest in the last few years. Thinned down to the monolayer limit they change from an indirect band structure to a direct band gap in the visible region. Due to the monolayer thickness the inversion symmetry of the crystal is broken and spin and valley are coupled to each other. The degeneracy between the two equivalent valleys, K and K', respectively, can be lifted by applying an external magnetic field. Here, we present photoluminescence measurements of CVDgrown tungsten disulphide (WS 2 ) monolayers at temperatures of 2 K. By applying magnetic fields up to 7 T in Faraday geometry, a splitting of the photoluminescence peaks can be observed. The magnetic field dependence of the A-exciton, the trion and three bound exciton states is discussed and the corresponding g-factors are determined.

Zeeman Splitting and Inverted Polarization of Biexciton Emission in Monolayer WS2

“…where µ B ≈ 58 µeV/T is the Bohr magneton, B is the magnetic field, and g S is the spectroscopic g factor of the emitting state, we obtain g XX S = −3.89 for the biexciton. The deduced spectroscopic g factor of the neutral exciton amounts to g X S = −3.82, in very close agreement to previous measurements on WS 2 [24,25,41] and almost identical to that of the biexciton. The red line in 2(c) marks a linear dependence with a g factor of −4 and serves as a guide to the eye.…”

Micro-Defects in Monolayer MoS2 Studied by Low-Temperature Magneto-Raman Mapping

“…In recent years, magneto-optical effects in 2D TMDs, such as valley Zeeman splitting, , valley- and spin-polarized Landau levels, magnetic field-modulated valley polarization, and valley coherence, − have been studied to further extend the application of TMDs in spintronics and valleytronics. Optical spectroscopic methods, such as circular polarized photoluminescence and magnetic circular dichroism, have been employed in the study of the magneto-optical effects in TMDs. − Recently, Raman spectroscopy has been demonstrated to be a feasible tool for investigating the magneto-optical effects in 2D TMDs. − A giant magneto-optical Raman effect was detected in MoS 2 by Ji et al, which was associated with magnetic field-induced symmetry breaking . However, these previous studies were carried out at 77 K and room temperature.…”

Plasmonic Effect on the Magneto-Optical Property of Monolayer WS2 Studied by Polarized-Raman Spectroscopy

“…In recent years, due to the potential device applications in spintronics and valleytronics, increasing research on the magneto-optical properties of 2D TMDs, such as valley Zeeman splitting [12,13], valley-and spin-polarized Landau levels [14], magnetic-field modulated valley polarization and valley coherence [15][16][17], has been carried out. Optical spectroscopic methods, such as circular polarized photoluminescence (PL) and magnetic circular dichroism (MCD) have been employed to study the magneto-optical properties of 2D TMDs [18][19][20][21]. Applying a magnetic field up to 7 T, a splitting for the PL peaks was observed in WS 2 [19].…”

“…Optical spectroscopic methods, such as circular polarized photoluminescence (PL) and magnetic circular dichroism (MCD) have been employed to study the magneto-optical properties of 2D TMDs [18][19][20][21]. Applying a magnetic field up to 7 T, a splitting for the PL peaks was observed in WS 2 [19]. Raman spectroscopy has been demonstrated to be a feasible tool to investigate the magneto-optical effect in 2D TMDs [22][23][24].…”