Sergei Zherlitsyn, HLD Dresden.
By investigating the Shastry-Sutherland compound SrCu2(BO3)2 up to the saturation magnetic field of 140 T and beyond, researchers from Japan, the Netherlands, and Switzerland together with scientists from the HLD have succeeded in identifying several spin-supersolid phases (SSPs) between the 1/2 magnetization plateau and saturation (1/1 plateau). The SSPs simultaneously break translational symmetry and the U(1) symmetry associated with the total Sz conservation. They all exhibit a diagonal stripe pattern with a certain period. The spin-lattice coupling plays an important role for the high-field properties of SrCu2(BO3)2. In this study, the researchers performed ultrasound and magnetostriction experiments, combined with the advanced high-magnetic-field generation equipment at the HLD-EMFL and at the ISSP of the University of Tokyo. They further supported their experimental data by extensive tensor-network calculations. They detected multiple anomalies in their experiments (Figure 1). Quite remarkably, the sound velocity of the 1/2 plateau exhibits a drastic decrease of -50 % (Figure 1a), related to a tetragonal-to-orthorhombic instability of the checkerboard-type magnon crystal. The magnetostriction results exhibit features similar to those of the magnetization; both start to increase when the spin gap closes (~ 25 T) and stay approximately constant in the plateau phases (Figures 1b and 1c). The unveiled nature of this paradigmatic quantum system is a new milestone for exploring exotic quantum states of matter emerging under extreme conditions. The very good agreement between theory and experiment regarding the saturation field and other critical fields demonstrates how these cutting-edge studies contribute to our better understanding of complex quantum systems. This establishes the combination of ultrasound and magnetostriction measurements with pulsed fields up to 150 T as a rather unique source of information in a field range scarcely explored so far. This opens very interesting perspectives for the study of other quantum magnets and, more generally, of other strongly correlated materials with exotic magnetic properties at ultrahigh magnetic fields.
Figure: Ultrahigh-field data (H // c) obtained in SrCu2(BO3)2: (a) sound velocity, (b) magnetostriction, and (c) magnetization. (d) Crystal structure in the ab plane with the dimer configuration built by Cu2+ ions with spin S = 1/2. (e) Spin pattern of the spinsupersolid state between Hc8 and Hc9, just below saturation. The bars represent the regions of magnetization plateaus.
Unveiling new quantum phases in the Shastry-Sutherland compound SrCu2(BO3) 2 up to the saturation magnetic field, T. Nomura, P. Corboz, A. Miyata, S. Zherlitsyn, Y. Ishii, Y. Kohama, Y. H. Matsuda, A. Ikeda, C. Zhong, H. Kageyama, and F. Mila,
Nat. Commun. 14, 3769 (2023).
https://www.nature.com/articles/s41467-023-39502-5
Contact: s.zherlitsyn@hzdr.de
