Signature of Faraday effect in Raman spectra of MoS₂

We perform Raman microscopy of a MoS₂ flake at 2K and in varying magnetic field (B), and for both parallel (VV) and perpendicular (VH) polarization configuration of polarizer and analyzer. We observe suppression of the A₁' Raman signal of MoS₂ in B=9T in the VH configuration. Raman maps were recorded in different B for both VV and VH configurations, and the intensity ratio of Raman signals A₁' and E' was inferred from them. The observed changes in suppression of A₁' are in good agreement with [1]. However, in [2] this change could only be detected at significantly higher B. Beside the influence of B on the oscillation modes of a crystal, one must also consider the impact of the Faraday effect. For this purpose, we recorded in addition a series of Raman spectra of the Si substrate as the function of B and polarization. The MoS₂ and Si peak ratios show approximately the same dependence on B, which indicates the dominant cause for the changes in the detected Raman signals being the Faraday effect. As the Faraday rotation angle is linear with B, it is straightforward to compensate it, which can even be automated in the cryogenic Raman microscope that we developed.