CrSBr, a van der Waals material, stands out as an air-stable magneticsemiconductor with appealing intrinsic properties such as crystallineanisotropy, quasi-1D electronic characteristics, layer-dependentantiferromagnetism, and non-linear optical effects. In this study, weinvestigate the differences between the absorption and emission spectra,focusing on the origin of the emission peak near 1.7 eV observed in thephotoluminescence spectrum of CrSBr. Our findings are corroborated byexcitation-dependent Raman experiments. Additionally, we explore theanti-Stokes Raman spectra and observe an anomalously high anti-Stokes to Stokesintensity ratio of up to 0.8, which varies significantly with excitation laserpower and crystallographic orientation relative to the polarization of thescattered light. This ratio is notably higher than that observed in graphene($\approx$ 0.1) and MoS$_2$ ($\approx$ 0.4), highlighting the uniquevibrational and electronic interactions in CrSBr. Lastly, we examine stimulatedRaman scattering and calculate the Raman gain in CrSBr, which attains a valueof 1 $\times$ 10$^{8}$ cm/GW, nearly four orders of magnitude higher than thatof previously studied three-dimensional systems.
We present photometric and spectroscopic observations of SN 2020xga and SN2022xgc, two hydrogen-poor superluminous supernovae (SLSNe-I) at $z = 0.4296$and $z = 0.3103$, respectively, which show an additional set of broad Mg IIabsorption lines, blueshifted by a few thousands kilometer second$^{-1}$ withrespect to the host galaxy absorption system. Previous work interpreted this asdue to resonance line scattering of the SLSN continuum by rapidly expandingcircumstellar material (CSM) expelled shortly before the explosion. The peakrest-frame $g$-band magnitude of SN 2020xga is $-22.30 \pm 0.04$ mag and of SN2022xgc is $-21.97 \pm 0.05$ mag, placing them among the brightest SLSNe-I. Weused high-quality spectra from ultraviolet to near-infrared wavelengths tomodel the Mg II line profiles and infer the properties of the CSM shells. Wefind that the CSM shell of SN 2020xga resides at $\sim 1.3 \times 10^{16}~\rmcm$, moving with a maximum velocity of $4275~\rm km~s^{-1}$, and the shell ofSN 2022xgc is located at $\sim 0.8 \times 10^{16}~\rm cm$, reaching up to$4400~\rm km~s^{-1}$. These shells were expelled $\sim 11$ and $\sim 5$ monthsbefore the explosions of SN 2020xga and SN 2022xgc, respectively, possibly as aresult of luminous-blue-variable-like eruptions or pulsational pair instability(PPI) mass loss. We also analyzed optical photometric data and modeled thelight curves, considering powering from the magnetar spin-down mechanism. Theresults support very energetic magnetars, approaching the mass-shedding limit,powering these SNe with ejecta masses of $\sim 7-9~\rm M_\odot$. The ejectamasses inferred from the magnetar modeling are not consistent with the PPIscenario pointing toward stars $> 50~\rm M_\odot$ He-core; hence, alternativescenarios such as fallback accretion and CSM interaction are discussed.