Sr $_3$ Ru $_2$ O $_7$的超净晶体在低温下经历变磁转变。该转变在所施加的场方向上显示出强的各向异性，其中临界场$H_c$的范围从$H\perp c$的$\sim 5.1$ T到$H\parallel c$的$\sim 8$ T。此外，对超纯样品的研究揭示了在$c$方向上的场的变磁力线的分叉，并且有人认为在磁化跳跃之间出现了一个反相。本研究的目的是解释这些现象的场方向各向异性。基于微观紧束缚模型，我们通过范霍夫奇异性方案引入了变磁跃迁。我们表明，O-八面体围绕c轴的旋转预期这种材料在平面内引入了交错的自旋轨道耦合，自然导致磁响应的各向异性。我们将低温相描述为前向散射过程所青睐的非稳态。自旋-轨道耦合对临界场$H_c$和相变的发生都有影响。
英文摘要：
Ultra-clean crystals of Sr$_3$Ru$_2$O$_7$ undergo a metamagnetic transition at low temperatures. This transition shows a strong anisotropy in the applied field direction with the critical field $H_c$ ranging from $\sim 5.1$T for $H\perp c$ to $\sim 8$T for $H\parallel c$. In addition, studies on ultra-pure samples revealed a bifurcation of the metamagnetic line for fields in $c$-direction and it is argued that a nematic phase emerges between the magnetization jumps. The aim of this study is to explain the field-direction anisotropy of these phenomena. Based on a microscopic tight-binding model, we introduce the metamagnetic transition by means of a van Hove singularity scenario. We show that the rotation of the O-octahedra around the c-axis expected for this material introduces a staggered spin-orbit coupling within the planes and naturally leads to an anisotropy of the magnetic response. We describe the low-temperature phase as a nematic state favored by forward scattering processes. The spin-orbit coupling shows an influence on both, the critical field $H_c$ and the occurrence of the nematic phase.
Elastic properties of hidden order in URu$_{\text2}$Si$_{\text2}$ are reproduced by a staggered nematic
我们发展了一个唯象平均场论，描述了在URu $_{\text2}$ Si $_{\text2}$中的隐藏顺序相位，作为沿$c$轴交错的$\text B_{\text{1g}}$表示的一个分支。几个实验功能再现由这个理论：拓扑结构的温度-压力相图，弹性模量$(C_{11}-C_{12})/2$以上的过渡在环境压力下的响应，和正交对称性破缺的高压反铁磁相。在这种情况下，隐序的特征在于沿$c$轴调制的旋转对称性破缺，高压相的主序是未调制的顺磁相，而将这两个相与高温顺磁相连接的三相点是Lifshitz点。
Tuning the magnetic properties of Kitaev materials via the antiferromagnetic proximity effect: Novel phases and application to an $α$-RuCl$_3$/MnPS$_3$ bilayer
Arizona State University（亚利桑那州立大学）；Munich Center for Quantum Science and Technology（慕尼黑量子科学与技术中心）
Chirality and quasi-long-range order in finite-flux Gutzwiller states for magnetized frustrated magnets
Kavli Institute for Theoretical Physics, University of California, Santa Barbara（加州大学圣塔芭芭拉分校卡弗里理论物理研究所）；Institute for Theoretical Physics, University of Cologne（科隆大学理论物理研究所）；Department of Physics and Astronomy, University of Utah（犹他大学物理与天文系）；Canadian Institute for Advanced Research（加拿大高级研究院）；French American Center for Theoretical Science, CNRS, KITP（法国美国理论科学中心，法国国家科学研究中心，KITP）
