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

TL;DR

This study visualizes the spatial structure of spin polarons in Zn-doped SrCu2(BO3)2 using NMR and theoretical calculations, revealing extended magnetic disturbances caused by impurities.

Contribution

First direct real-space imaging of spin polarons in a frustrated quantum magnet using combined NMR and exact diagonalization techniques.

Findings

Identification of 15 boron sites affected by Zn impurities

Mapping of local magnetization distribution around impurities

Evidence of extended spin polaron structure

Abstract

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 11B nuclear magnetic resonance spectrum exhibits 15 additional boron sites near non-magnetic 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.