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arXiv · 2609.06472

NMR evidence of pressure-induced structural transition and enhanced spin fluctuations up to 14~GPa in SrCu$_2$(BO$_3$)$_2$

Zhanlong Wu·Kefan Du·Shuo Li·Tong Shi·Ying Chen·Qingxin Dong·Rui Zhou·Rong Yu·Juanjuan Liu·Bosen Wang·Jinguang Cheng·Weiqiang Yu·Yi Cui
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Abstract

The Shastry-Sutherland compound SrCu$_2$(BO$_3$)$_2$ has attracted considerable interest as a platform for exploring quantum phases and quantum phase transitions driven by magnetic frustration. The pressure-induced structural and magnetic phase transitions in SrCu$_2$(BO$_3$)$_2$, however, remain controversial. To address this issue, we performed high-pressure $^{11}$B nuclear magnetic resonance (NMR) measurements on SrCu$_2$(BO$_3$)$_2$ up to 14~GPa. The NMR spectra reveal two pressure-induced monoclinic phases. With pressure above 4~GPa and with temperature below 10~K, the rapid broadening of the NMR spectrum and the power-law behavior in the spin-lattice relaxation rate $1/T_1$ provide clear evidence for a gapless 3D antiferromagnetic (AFM) phase in the monoclinic phase. At an intermediate temperature range around 20~K, the emergence of the field-dependent NMR line splits resolves a two-dimensional, short-range ordered AFM phase; at temperature above 30~K, the sublinear power-law behavior of $1/T_1$ identifies an extended correlated paramagnetic regime.

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Zhanlong Wu, Kefan Du, Shuo Li, Tong Shi, Ying Chen, Qingxin Dong, Rui Zhou, Rong Yu, Juanjuan Liu, Bosen Wang, Jinguang Cheng, Weiqiang Yu, Yi Cui. 2026-09-06. NMR evidence of pressure-induced structural transition and enhanced spin fluctuations up to 14~GPa in SrCu$_2$(BO$_3$)$_2$. https://arxiv.org/abs/2609.06472

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