Kagome Antiferromagnets Exhibit 1/9 Magnetization Plateau with Dirac-like Spinons, Revealing Exotic Phases
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Kagome lattice antiferromagnets present a fascinating challenge to condensed matter physicists, exhibiting a wealth of unusual magnetic phases, and recent experiments have revealed a particularly intriguing state at a specific magnetic field, known as a magnetization plateau. Tanja Đurić, Pinaki Sengupta, and colleagues at Nanyang Technological University and Boston University investigate the nature of this plateau, which remains controversial due to the complex interplay of geometrical frustration and exotic quantum phenomena. Their research demonstrates that the ground state at the plateau arises from an instability, leading to a gapless chiral spin density wave, and crucially, reveals this spin order originates from a correlated state with nontrivial topological properties. This discovery provides a significant step forward in understanding these complex materials and offers new insights into the behaviour of quantum magnetism in frustrated systems. Particularly interesting states appear at the 1/9 magnetization plateau, where the system displays unusual behaviour. Researchers investigate the emergence of a 2kF instability and chiral spin density wave order at this plateau, seeking to understand the underlying mechanisms driving these phases. The study employs theoretical calculations to explore the stability of different spin configurations and to determine the conditions under which the 2kF instability and chiral spin density wave order emerge.
Results demonstrate that the 2kF instability arises from specific interactions between the spins, and the chiral spin density wave order is stabilized by a combination of these interactions and geometric frustration inherent to the kagome lattice. This work provides insights into the complex magnetic behaviour of kagome antiferromagnets and contributes to a broader understanding of correlated electron systems. Recent studies have observed a magnetic field-induced 1/9 magnetization plateau in several materials. The nature and exotic physical properties of this plateau remain controversial due to the geometrical frustration inherent to the system. Torque magnetometry measurements on YCOB single-crystal samples indicate the presence of Dirac-like spinons at this plateau. Researchers are now using novel machine learning techniques to study the properties of this state. Kagome Materials and Charge Density Wave Formation A significant body of research focuses on Kagome lattice materials, such as AV3Sb5, and the emergence of charge density waves within them. Investigations explore the mechanisms driving CDW formation, including the role of electron interactions and symmetry breaking. Studies also focus on the characteristics of the CDW, such as its wavevector and spatial modulation, and the connection between CDW and superconductivity. Researchers are actively determining whether the CDW competes with or enhances superconductivity, employing both experimental observation and theoretical modelling to understand these relationships.
This research also extends to the investigation of topological phases and quantum materials. Scientists explore the possibility of topological insulators and semimetals in Kagome materials, searching for Dirac and Weyl semimetals and examining their unique surface states. Several papers focus on the concept of fractionalization, where electrons break down into emergent quasiparticles, and its connection to spin liquid phases characterized by long-range entanglement. The concept of Chern numbers and Berry phases is used to characterize the topological properties of electronic bands and predict quantized transport phenomena. Researchers are also investigating strongly correlated electron systems and novel phases. They investigate the validity of Luttinger’s theorem in these systems and explore the possibility of Fermi surface reconstruction due to electron-electron interactions. The formation and properties of spin density waves are investigated, often in relation to competition with other ordered phases. The emergence of non-Fermi liquid behaviour is also explored, often in the context of quantum criticality and the breakdown of conventional quasiparticle descriptions. Advanced computational methods, such as Density Matrix Renormalization Group, and machine learning techniques are increasingly used to analyze data and discover new patterns in complex materials. First-principles calculations based on density functional theory are used to calculate electronic structure and predict material properties. Investigations into Friedel oscillations, spatial modulations of electron density, provide insights into the electronic structure and interactions within the material. Kagome lattice materials are at the forefront of condensed matter physics research due to their unique electronic structure and the emergence of novel phases, including CDWs, superconductivity, and potentially topological states. Understanding the interplay between different ordered phases is crucial for designing new materials with desired properties. Topological concepts are increasingly being used to understand and predict the behaviour of strongly correlated electron systems. Computational and machine learning tools are essential for analyzing data and discovering new patterns in complex materials. The breakdown of conventional Fermi liquid theory is a common feature of strongly correlated systems, and understanding the origins of non-Fermi liquid behaviour is a major challenge. Friedel oscillations are being used as a tool to probe the electronic structure and interactions in materials, providing insights into their behaviour.
Chiral Spin Density Wave at One-Ninth Magnetization This research establishes a novel understanding of the complex magnetic behaviour observed in kagome antiferromagnets, specifically at the 1/9 magnetization plateau. By combining advanced computational techniques, variational Monte Carlo, symmetry enhanced neural network states, and a flux insertion method, scientists determined the ground state at this plateau is a gapless chiral spin density wave. This finding challenges previous interpretations suggesting quantum spin liquid or valence bond crystal ground states, and instead points to an instability within the underlying composite Fermi liquid that drives the observed spin order.
The team’s calculations reveal this spin density wave arises from a 2kF instability, evidenced by a finite chiral order parameter and distinct features in the spin structure factor. Notably, the resulting magnetic order exhibits a 1×1 density wave pattern, mirroring similar charge density wave ordering found in related kagome metals. This work provides a comprehensive picture of the magnetic state, explaining the emergence of unconventional magnetic oscillations detected in recent experimental studies of YCOB single crystals. The authors acknowledge that the complexity of the system necessitates further investigation into the role of interactions between composite fermions, and the precise impact of the emergent gauge field. Future research could explore the behaviour of this chiral spin density wave under varying conditions, and investigate its potential connection to other exotic quantum states predicted for kagome lattices. 👉 More information 🗞 2 instability and chiral spin density wave at the 1/9 magnetization plateau in the kagome antiferromagnets 🧠 ArXiv: https://arxiv.org/abs/2512.11670 Tags: