Giant and anisotropic many-body spin-orbit tunability in a strongly correlated kagome magnet (1810.00218v1)

Abstract: Owing to the unusual geometry of kagome lattices-lattices made of corner-sharing triangles-their electrons are useful for studying the physics of frustrated, correlated and topological quantum electronic states. In the presence of strong spin-orbit coupling, the magnetic and electronic structures of kagome lattices are further entangled, which can lead to hitherto unknown spin-orbit phenomena. Here we use a combination of vector-magnetic-field capability and scanning tunnelling microscopy to elucidate the spin-orbit nature of the kagome ferromagnet Fe3Sn2 and explore the associated exotic correlated phenomena. We discover that a many-body electronic state from the kagome lattice couples strongly to the vector field with three-dimensional anisotropy, exhibiting a magnetization-driven giant nematic (two-fold-symmetric) energy shift. Probing the fermionic quasi-particle interference reveals consistent spontaneous nematicity-a clear indication of electron correlation-and vector magnetization is capable of altering this state, thus controlling the many-body electronic symmetry. These spin-driven giant electronic responses go well beyond Zeeman physics and point to the realization of an underlying correlated magnetic topological phase. The tunability of this kagome magnet reveals a strong interplay between an externally applied field, electronic excitations and nematicity, providing new ways of controlling spin-orbit properties and exploring emergent phenomena in topological or quantum materials.

• The paper demonstrates a giant nematic energy shift of up to 12 meV driven by magnetization in Fe3Sn2.
• The paper reveals a pronounced anisotropic magnetic response with an effective g-factor of approximately 210, surpassing conventional Zeeman effects.
• The paper uses vector-magnetic-field STM to uncover tunable electronic symmetry and hourglass-like dispersion, informing future quantum device design.

Anisotropic Many-Body Spin-Orbit Phenomena in a Kagome Magnet

This paper presents a comprehensive investigation into the complex interplay between spin-orbit coupling (SOC) and electronic correlation phenomena in the kagome ferromagnet Fe$_3$Sn$_2$. Utilizing vector-magnetic-field scanning tunnelling microscopy (STM), the authors explore the unique spin-orbit phenomena that arise in this system, emphasizing the significant tunability of electronic properties through magnetization.

The kagome lattice, characterized by its coordination of corner-sharing triangles, provides a fascinating environment to paper correlated and topological quantum states. In Fe$_3$Sn$_2$, the large spin-orbit coupling entangles magnetic and electronic structures, potentially leading to novel phases. A salient feature uncovered in the paper is a magnetization-driven giant nematic energy shift in the electronic states, which is beyond what is typically explained by Zeeman physics alone. This effect indicates a profound level of tunability via the vector field, revealing a strongly correlated magnetic topological phase.

Key Findings

• Giant Nematic Energy Shift: A detailed analysis demonstrates that a nematic two-fold symmetric energy shift is driven by magnetization in FeSn surfaces of the material, accompanied by a rotation angle-dependent modulation. The energy-shift magnitude recorded reaches up to 12 meV, and the effective g-factor derived from initial shifts is exceptionally large at approximately 210, surpassing previous literature values.
• Anisotropic Magnetic Response: Experimental results highlight a notable anisotropy in the magnetic responses of the electronic states, where the electronic nematicity aligns or breaks based on magnetization direction. This result underscores strong SOC effects intertwined with magnetism, revealing topological characteristics distinct from conventional models like the Kane-Mele picture.
• Quasiparticle Interference and Symmetry: Quasiparticle interference (QPI) measurements show spontaneous nematicity breaking with a two-fold symmetry that aligns with the a-axis of the sample in zero fields. Magnetization enables control over this symmetry, highlighting the interconnection of electronic symmetry and magnetization. Additionally, QPI data indicate an hourglass-like dispersion feature, suggesting a massive Dirac-like band structure.

Implications and Future Directions

This paper opens pathways for further exploration of spin-orbit coupled systems with enhanced sensitivity to external fields. By demonstrating the feasible control of electronic states via vector magnetization, the findings contribute to a deeper understanding of correlated quantum materials' dynamics. The stratified response of the kagome lattice under varying magnetic conditions could inform the design of future quantum devices and materials with customizable electronic properties.

The identification of a giant and anisotropic electronic response in Fe$_3$Sn$_2$ aligns with theoretical predictions of unusual states in kagome-based systems, providing an experimental platform for investigating the topology of correlated matter. The paper signifies a potential leap in designing materials with precise control over their spin, charge, and orbital interactions, crucial for developing next-generation quantum technologies.

In conclusion, the paper provides compelling evidence for complex SOC-tunable phenomena in the kagome magnet Fe$_3$Sn$_2$. Investigations into such materials are expected to propel theories on strongly correlated electron systems, potentially revealing new states of matter that involve intricate relationships between geometric frustration, electronic correlation, and SOC. Further studies, possibly extending to different material systems or integrating advanced computational models, are encouraged to broaden the understanding of such magnetic topological phenomena.