Emergent bound states and impurity pairs in chemically doped Shastry-Sutherland system.

Shi, Zhenzhong; Steinhardt, William; Graf, David; Corboz, Philippe; Weickert, Franziska; Harrison, Neil; Jaime, Marcelo; Marjerrison, Casey et al. · Nat Commun · 2019

basic_science · Level V

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Abstract

Impurities often play a defining role in the ground states of frustrated quantum magnets. Studies of their effects are crucial in understanding of the phase diagram in these materials. SrCu<sub>2</sub>(BO<sub>3</sub>)<sub>2</sub>, an experimental realization of the Shastry-Sutherland (SS) lattice, provides a unique model system for such studies using both experimental and numerical approaches. Here we report effects of impurities on the crystals of bound states, and doping-induced emergent ground states in Mg-doped SrCu<sub>2</sub>(BO<sub>3</sub>)<sub>2</sub>, which remain stable in high magnetic fields. Using four complementary magnetometry techniques and theoretical simulations, a rich impurity-induced phenomenology at high fields is discovered. The results demonstrate a rare example in which even a small doping concentration interacts strongly with both triplets and bound states of triplets, and thus plays a significant role in the magnetization process even at high magnetic fields. Our findings provide insights into the study of impurity effects in geometrically frustrated quantum magnets.