近日，美国加州大学圣巴巴拉分校的Andrea F. Young及其研究团队取得一项新进展。经过不懈努力，他们对菱形三层石墨烯中的谷间相干和本征自旋轨道耦合进行了研究。相关研究成果已于2024年7月1日在国际知名学术期刊《自然—物理学》上发表。
该研究团队揭示了谷不平衡轨道铁磁体和谷间相干态之间的微妙竞争，其中两个动量空间谷中的电子波函数发表现出宏观相干的相对相位。研究人员专注于四分之一金属体系中的菱形三层，该结构表现出自发破缺的自旋与谷-同位旋对称性费米表面。通过应用局部磁强计和全局电荷传感技术，研究人员比较了谷相干相和谷不平衡相的平面内自旋磁化率，揭示了石墨烯的本征自旋轨道耦合的影响，该耦合驱动了一个独特的相关相的出现，即它们的杂化。
自旋轨道耦合还抑制了谷不平衡相的面内磁化率，使他们可以提取出六方氮化硼封装石墨烯体系的自旋轨道耦合强度约为50μeV。此外，他们还讨论了在菱形和扭曲石墨烯多层中观察到的，自旋-轨道耦合对自旋-三重态超导体的影响。
据悉，菱形石墨烯多层为探索强相互作用电子系统中超导性和磁性的出现，提供了一个洁净且高度可重复的平台。
附：英文原文
Title: Intervalley coherence and intrinsic spin–orbit coupling in rhombohedral trilayer graphene
Author: Arp, Trevor, Sheekey, Owen, Zhou, Haoxin, Tschirhart, C. L., Patterson, Caitlin L., Yoo, H. M., Holleis, Ludwig, Redekop, Evgeny, Babikyan, Grigory, Xie, Tian, Xiao, Jiewen, Vituri, Yaar, Holder, Tobias, Taniguchi, Takashi, Watanabe, Kenji, Huber, Martin E., Berg, Erez, Young, Andrea F.
Issue&Volume: 2024-07-01
Abstract: Rhombohedral graphene multilayers provide a clean and highly reproducible platform to explore the emergence of superconductivity and magnetism in a strongly interacting electron system. Here we reveal a subtle competition between valley-imbalanced orbital ferromagnets and intervalley-coherent states in which electron wavefunctions in the two momentum-space valleys develop a macroscopically coherent relative phase. We focus on a rhombohedral trilayer in the quarter-metal regime—where there is a single Fermi surface that spontaneously breaks spin and valley-isospin symmetry—and employ local magnetometry and global charge sensing techniques. Comparing the in-plane spin susceptibility of the intervalley-coherent and valley-imbalanced phases reveals the influence of graphene’s intrinsic spin–orbit coupling, which drives the emergence of a distinct correlated phase that is their hybrid. Spin–orbit coupling also suppresses the in-plane magnetic susceptibility of the valley-imbalanced phase, allowing us to extract the spin–orbit-coupling strength of approximately 50μeV for our hexagonal-boron-nitride-encapsulated graphene system. We discuss the implications of a finite spin–orbit coupling on the spin-triplet superconductors observed in both rhombohedral and twisted graphene multilayers.
DOI: 10.1038/s41567-024-02560-7
Source: https://www.nature.com/articles/s41567-024-02560-7