Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, Japan.
Tokyo Denki University, Adachi, Tokyo, Japan.
Nat Commun. 2023 Jun 24;14(1):3769. doi: 10.1038/s41467-023-39502-5.
Under magnetic fields, quantum magnets often undergo exotic phase transitions with various kinds of order. The discovery of a sequence of fractional magnetization plateaus in the Shastry-Sutherland compound SrCu(BO) has played a central role in the high-field research on quantum materials, but so far this system could only be probed up to half the saturation value of the magnetization. Here, we report the first experimental and theoretical investigation of this compound up to the saturation magnetic field of 140 T and beyond. Using ultrasound and magnetostriction techniques combined with extensive tensor-network calculations (iPEPS), several spin-supersolid phases are revealed between the 1/2 plateau and saturation (1/1 plateau). Quite remarkably, the sound velocity of the 1/2 plateau exhibits a drastic decrease of -50%, related to the tetragonal-to-orthorhombic instability of the checkerboard-type magnon crystal. The unveiled nature of this paradigmatic quantum system is a new milestone for exploring exotic quantum states of matter emerging in extreme conditions.
在磁场下，量子磁体经常经历具有各种有序的奇特相变。在 Shastry-Sutherland 化合物 SrCu(BO)中发现的分数磁化平台序列在量子材料的高场研究中发挥了核心作用，但到目前为止，该系统只能在磁化强度的饱和值的一半进行探测。在这里，我们报告了对该化合物的首次实验和理论研究，直至 140 T 及以上的饱和磁场。我们使用超声和磁致伸缩技术结合广泛的张量网络计算（iPEPS），在 1/2 平台和饱和（1/1 平台）之间揭示了几个自旋超固体相。非常显著的是，1/2 平台的声速急剧下降了-50%，这与棋盘型磁子晶体的四方到正交的不稳定性有关。这个典型量子系统的揭示性质是探索在极端条件下出现的奇异物质量子态的一个新的里程碑。
