Real Space Imaging of Spin Polarons in Zn-Doped SrCu2(BO3)(2)

We report on the real space profile of spin polarons in the quasi-two-dimensional frustrated dimer spin system SrCu2(BO3)(2) doped with 0.16% of Zn. The B-11 nuclear magnetic resonance spectrum exhibits 15 additional boron sites near nonmagnetic Zn impurities. With the help of exact diagonalizations of finite clusters, we have deduced from the boron spectrum, the distribution of local magnetizations at the Cu sites with fine spatial resolution, providing direct evidence for an extended spin polaron. The results are confronted with those of other experiments performed on doped and undoped samples of SrCu2(BO3)(2).