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## Probing Electron Interactions in a Two-Dimensional System by Quantum Magneto-Oscillations

We have experimentally studied the renormalized effective mass m* and Dingle temperature TD in two spin subbands with essentially different electron populations. Firstly, we found that the product m*T_D that determines the damping of quantum oscillations, to the first approximation, is the same in the majority and minority subbands even at a spin polarization degree as high as 66%. This result confirms the theoretical predictions that the interaction takes place at high energies ~EF rather than within a narrow strip of energies EF ± kBT . Secondly, to the next approximation, we revealed a difference in the damping factor of the two spin subbands, which causes skewness of the oscillation line shape. In the absence of the in-plane magnetic field , the damping factor m*T_D is systematically smaller in the spin-majority subband. The difference, quantified with the skew

factor γ = (TD↓ − TD↑)/2T_D0 can be as large as 20%. The skew factor tends to decrease as B or temperature grow, or B⊥ decreases; for low electron densities and high in-plane fields, the skew factor even changes sign. Finally, we compared the temperature and magnetic field dependencies of the magneto-oscillation amplitude with predictions of the interaction correction theory, and found, besides some qualitative similarities, several quantitative and qualitative differences. To explain qualitatively our results, we suggested an empirical model that assumes the existence of easily magnetized triplet scatterers on the Si/SiO2 interface.