Interplay between Relativistic Spin-Momentum Locking and Breaking of Inversion Symmetry: conditions for p-wave magnetism
Institute of Physics, Polish Academy of Sciences（波兰科学院物理研究所）；Consiglio Nazionale delle Ricerche (CNR-SPIN)（国家研究委员会（CNR-SPIN））；International Research Centre Magtop（Magtop国际研究中心）；Department of Materials Science, University Milan-Bicocca（米兰比可卡大学材料科学系）；SPIN-CNR, UOS Salerno（SPIN-CNR萨莱诺联合操作站）
Amar Fakhredine, Giuseppe Cuono, Jan Skolimowski, Silvia Picozzi, Carmine Autieri
We investigate the interplay between relativistic spin-momentum locking arising from altermagnetism and various forms of inversion symmetry breaking. Depending on the symmetry breaking, this can give rise to Rashba-type spin-orbit coupling (SOC), Weyl-type SOC, or the coexistence of two distinct spin-momentum lockings. We focus on the altermagnetic Ca2RuO4 as a testbed material. Our results reproduce the experimentally observed ground state, which is an A-centered magnetic order with the Neel vector along the b-axis, hosting spin cantings along the a- and c-axes but without weak ferromagnetism. Ca2RuO4 exhibits relativistic spin-momentum locking, with different even-parity wave orders for the three spin components. We interpret the experimental results on doped samples as evidence for a transition from a pure altermagnetic phase to a weak ferromagnetic phase. Under ferroelectric- and antiferroelectric-like distortions, there are no qualitative changes in the non-relativistic spin-momentum locking and in the weak ferromagnetism. However, we observe the rise of the Rashba or Weyl-type SOC. Using numerical and analytical models, we investigate which nodal planes persist when inversion symmetry is broken in the relativistic case. The spin-momentum locking of the other components adopt a p-wave character in the case of Rashba; in contrast, Weyl-type SOC disrupts all nodal planes, leaving only nodal lines. Finally, to simulate a stripe phase with structural distortions along the z-axis, we studied a modulated electric field inducing atomic displacements within one Ca2RuO4 layer. This produces a magnetic phase transition to an exotic altermagnetic state with two non-relativistic spin-momentum lockings hosting weak ferromagnetism. Our research presents a comprehensive analysis of various possible scenarios in altermagnets with breaking of inversion symmetries under relativistic effects
Momentum-inversion symmetry breaking on the Fermi surface of magnetic topological insulators
磁性拓扑绝缘体（MnBi $_2$ Te $_4$）（Bi $_2$ Te $_3$）$_n$被预期表现出磁能隙，而最近的光谱研究没有观察到它们。因此，地球表面的磁性仍在争论之中。在这项工作中，我们提出了另一个对称性标准来探测表面磁性。由于同时存在时间反演的自旋破缺和反转的自旋破缺，我们证明了表面能带结构违反了动量反转对称性，如果相应的表面态与表面磁性强耦合，则费米表面将出现三重而不是六重旋转对称性.对于（0001）面上的表面带，这种动量反转对称性破坏沿$Γ-K$方向是显著的。
Symmetry-protected nodal planes and accidental nodal surfaces in mixed odd-even wave spin-momentum locking of relativistic altermagnets
International Research Centre Magtop, Institute of Physics, Polish Academy of Sciences（波兰科学院物理研究所磁顶国际研究中心）；Institute of Physics, Polish Academy of Sciences（波兰科学院物理研究所）；School of Quantum Physics and Matter, Institute for Research in Fundamental Sciences (IPM)（基础科学研究所量子物质学院）；SPIN-CNR, UOS Salerno（萨莱诺大学自旋-意大利国家研究委员会中心）
Unconventional Magnetism: Symmetry Classification, Hybrid-parity and Unconstrained-parity Classes
Anhui Province Key Laboratory of Low-Energy Quantum Materials and Devices, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences（中国科学院合肥物质科学研究院）；School of Physical Science and Technology, Inner Mongolia University（内蒙古大学物理科学与技术学院）；Institute of Physical Science and Information Technology, Anhui University（安徽大学物理与材料科学学院）；Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences（中国科学院合肥物质科学研究院固体物理研究所）；Research Center for Quantum Physics and Technologies, Inner Mongolia University（内蒙古大学量子物理与技术研究中心）；Inner Mongolia Key Laboratory of Microscale Physics and Atomic Manufacturing, Inner Mongolia University（内蒙古微尺度物理与原子制造重点实验室）；Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology（北京理工大学物理学院）
Direct evidence of hidden local spin polarization in a centrosymmetric superconductor LaO$_{0.55}$F$_{0.45}$BiS$_2$
传统的Rashba自旋极化是由强自旋轨道相互作用（SOI）和空间反转不对称性的组合引起的。尽管LaOBiS $_2$系统具有中心对称的晶体结构，但最近的理论预测LaOBiS系统中存在Rashba和Dresselhaus型自旋分裂态，这是由于激活BiS $_2$层的局域反转不对称性造成的.利用高分辨自旋和角分辨光电子能谱研究了LaO $_{0.55}$ F $_{0.45}$ BiS $_2$的电子能带结构和自旋织构。我们的研究为价带和导带在X点附近的局域自旋极化提供了直接的光谱证据。特别是在导带中首次观察到了类Rashba和类Dresselhaus自旋织构的共存。这一发现对于双栅自旋场效应晶体管（SFET）的制备具有重要意义。此外，自旋分裂带导致自旋-动量锁定费米面，由此出现新的超导性。我们的实验不仅拓展了自旋电子材料的研究范围，而且加深了人们对SOI相关超导性的理解。
Strain-tunable multipiezo effects in Janus monolayer Cr2SSe: Selective reversal of valley polarization and single-spin-channel anomalous valley Hall effect
Multiferroicity induced by dislocated spin-density waves
我们发现了一个新的途径走向多铁性，显示如何磁性可以驱动铁电性，而不依赖于反转对称性破缺的磁序。我们的自由能分析表明，任何相称的自旋密度波有序的相位位错，即使它是共线的，引起电极化的强度。由于位错的存在，电子中心、磁性中心和反转中心不重合，这是多铁性耦合的充分条件。新的机制解释了形成的多铁性相的磁性可磁化性转变，如观察到的YMn $_{2}$ O $_{5}$和相关化合物。我们预测，在这些多铁性材料中，振荡的电极化是伴随着均匀极化。在此基础上，我们提出了具有铁电性的新型磁性材料。
Coupled Real- and Momentum-Space Topology in Symmetry-Locked Bilayer Altermagnet
Hebei University of Technology（河北工业大学）；Arizona College of Technology at Hebei University of Technology（河北工业大学亚利桑那科技学院）；Hebei Engineering Laboratory of Photoelectronic Functional Crystals, Hebei University of Technology（河北工业大学光电功能晶体河北省重点实验室）
Coupled spin-valley, Rashba effect and hidden persistent spin polarization in WSi$_2$N$_4$ family
实验成功地合成了新型二维材料MoSi $_2$ N $_4$和WSi $_2$ N $_4$，并从理论上预测了各种类似结构。在这里，我们报告的电子性质，特别关注的带分裂WA $_2$ Z $_4$（A=Si，Ge; Z=N，P，As），使用国家的最先进的密度泛函理论和多体微扰理论（在G $_0$ W $_0$和BSE的框架内）。由于反转对称性破缺和强的自旋轨道耦合效应，我们在第一布里渊区（BZ）的拐角处检测到耦合的自旋谷效应。此外，我们观察到立方和线性分裂带周围的$Γ$和M点，分别。有趣的是，面内镜像对称性（$σ_h$）和任意$k$点的约化对称性，强制持续自旋织构（PST）发生在整个BZ。我们诱导Rashba分裂通过打破$σ_h$通过一个面外电场（EEF）。W原子的反转非对称性在中心对称层状体材料中引入了隐藏的自旋极化。因此，自旋层锁定效应，即能量退化的相反自旋空间上分离的顶部和底部W层，已被确定。我们的低能$k.p$模型表明，沿M-K线的PST对EEF和层厚度是鲁棒的，使得它们适合于自旋电子学和谷电子学中的应用。
