Diluted magnetic semiconductors are materials well known to exhibit strong correlations which typically manifest in carrier-mediated magnetic ordering. In this Rapid Communication, we show that the interaction between excitons and magnetic impurities in these materials is even strong enough to cause a significant deviation from the bare exciton picture in linear absorption spectra of quantum well nanostructures. It is found that exciton-impurity correlations induce a characteristic fingerprint in the form of an additional side structure close to the exciton resonance in combination with a shift of the main exciton line of up to a few meV. We trace back these structures to the form of the self-energy and demonstrate that reliable values of the average correlation energy per exciton can be extracted directly from the spectra. Since the only requirement for our findings is sufficiently strong correlations, the results can be generalized to other strongly correlated systems.Many-body correlations are an important and extensively studied phenomenon in many areas of physics [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15], the impact of which is typically investigated using nonlinear response such as four-wave mixing [16][17][18][19][20][21]. An interesting subclass of materials that are known for strong correlation effects are diluted magnetic semiconductors (DMSs), i.e., II-VI or III-V semiconductor alloys with a small percentage of magnetic dopants, typically manganese [22][23][24][25][26]. Most notably in these materials, correlations have been found to cause carrier-mediated ferromagnetic ordering [27], a topic which is still actively investigated [6]. DMSs are also known for possible applications in the field of spintronics [28][29][30][31][32], either as a spin aligner [33] or in terms of data storage applications [34].The physics in DMSs is typically dominated by the strong exchange interaction between carriers and magnetic dopants which is usually modeled by a Kondo-type Hamiltonian for electrons and holes with well-established coupling constants [25]. Since typical experiments on DMS nanostructures are performed close to the exciton resonance [35][36][37][38][39][40][41][42], it is evident that effects due to the Coulomb interaction cannot be neglected. In addition, it was already pointed out in the literature that a meanfield treatment of the electron-impurity exchange interaction is often insufficient for an accurate description of ultrafast spin dynamics [43,44] as well as order parameters [6,45].In this Rapid Communication we explore the impact of exciton-impurity correlations on linear absorption spectra of DMS nanostructures close to the exciton resonance. Considering that carrier-impurity correlations typically manifest themselves in the dynamical properties of DMSs such as spin overshoots on picosecond time scales [43,46] or modifications of spin-transfer rates [47], it is often challenging to pinpoint these features in experiments since they can be extremely dependent on the particular sample. Thi...
