Sr$_2$RuO$_4$表面层中磁场可调的交织棋盘格电荷序与向列序
Magnetic-Field Tunable Intertwined Checkerboard Charge Order and Nematicity in the Surface Layer of Sr$_2$RuO$_4$
AI总结：
本文证明Sr$_2$RuO$_4$表面层中RuO$_6$八面体旋转产生交织的向列序与棋盘格电荷序，磁场可调控van Hove奇点并在约32T诱发Lifshitz相变。
摘要：
在强关联电子材料中，电子、自旋和电荷自由度紧密交织。这通常会导致稳定涌现的序，这些序对外部物理刺激高度敏感，为技术应用带来了广阔前景。在钙钛矿型钌酸盐中，这种敏感性表现为物理性质随RuO$_6$八面体细微结构细节的剧烈变化，从而稳定了神秘的关联基态，涵盖从备受争议的超导态、电子向列序、变磁量子临界性到铁磁性。本文证明，Sr$_2$RuO$_4$表面层中RuO$_6$八面体的旋转产生了体材料中未观察到的新涌现序。通过对低能电子态进行原子尺度光谱表征，在费米能附近识别出四个van Hove奇点。这些奇点可直接与交织的向列序和棋盘格电荷序联系起来。研究证明了磁场可对其中一个van Hove奇点进行调控，这表明表面层在约32T的磁场下发生Lifshitz相变。这些结果确立了Sr$_2$RuO$_4$表面层作为一个令人兴奋的2D关联电子系统，并突显了在这些系统中工程化低能电子态的机遇。
英文摘要：
In strongly correlated electron materials, the electronic, spin, and charge degrees of freedom are closely intertwined. This often leads to the stabilization of emergent orders that are highly sensitive to external physical stimuli promising opportunities for technological applications. In perovskite ruthenates, this sensitivity manifests in dramatic changes of the physical properties with subtle structural details of the RuO$_6$ octahedra, stabilizing enigmatic correlated ground states, from a hotly debated superconducting state via electronic nematicity and metamagnetic quantum criticality to ferromagnetism. Here, it is demonstrated that the rotation of the RuO$_6$ octahedra in the surface layer of Sr$_2$RuO$_4$ generates new emergent orders not observed in the bulk material. Through atomic-scale spectroscopic characterization of the low-energy electronic states, four van Hove singularities are identified in the vicinity of the Fermi energy. The singularities can be directly linked to intertwined nematic and checkerboard charge order. Tuning of one of these van Hove singularities by magnetic field is demonstrated, suggesting that the surface layer undergoes a Lifshitz transition at a magnetic field of ~32T. The results establish the surface layer of Sr$_2$RuO$_4$ as an exciting 2D correlated electron system and highlight the opportunities for engineering the low-energy electronic states in these systems.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
