Quantum interactions in topological R166 kagome magnet

Abstract

Kagome magnet has been found to be a fertile ground for the search of exotic quantum states in condensed matter. Arising from the unusual geometry, the quantum interactions in the kagome lattice give rise to various quantum states, including the Chern-gapped Dirac fermion, Weyl fermion, flat band and van Hove singularity. Here we review recent advances in the study of the R166 kagome magnet (RT6E6, R = rare earths; T = transition metals; and E = Sn, Ge, etc) whose crystal structure highlights the transition-metal-based kagome lattice and rare-earth sublattice. Compared with other kagome magnets, the R166 family owns the particularly strong interplays between the d electrons on the kagome site and the localized f electrons on the rare-earth site. In the form of spin-orbital coupling, exchange interaction and many-body effect, the quantum interactions play an essential role in the Berry curvature in both the reciprocal and real spaces of R166 family. We discuss the spectroscopic and transport visualization of the topological electrons hosted in the Mn kagome layer of RMn6Sn6 and the various topological effects due to the quantum interactions, including the Chern-gap opening, the exchange-biased effect, the topological Hall effect and the emergent inductance. We hope this work serves as a guide for future explorations of quantum magnets.

Crystal growth, magnetic and electrical transport properties of the kagome magnet RCr6Ge6 (R = Gd–Tm)

“…[43,45,47] These compounds contain two magnetic sublattices, one from the rare-earth atom R and the other from the transition metal atom Cr (magnetic moment around 0.2 µ B /Cr under a magnetic 077501-3 field). Unlike the Mn-based 166 compound, with exchange parameters J Mn−Mn J R−Mn J R−R , [3] the Cr-Cr interaction is too weak here for 3d moment formation, and the moment on the kagome lattice requires the polarizing influence of the molecular field of the ordered R moments. The antiferromagnetic J R−Mn competes with the preferred orientations of each sublattice, leading to a non-collinear, canted ferrimagnetic structure.…”

“…The kagome lattice, consisting of triangles with shared corners, has garnered widespread attention in recent years. [1][2][3] It simultaneously favors frustrated magnetism and topological quantum states, and can host various exotic physical phases including unconventional superconductivity, [4][5][6] charge density waves, [7][8][9][10][11] Wigner crystals, [12] the fractional quantum Hall effect [13,14] and quantum spin liquids. [15,16] In addition, frustrated magnetism itself can result in exotic spin whirls, [17] which are potentially applicable in spintronic devices.…”

“…[18,19] The 166 kagome compound, with a general formula RT 6 X 6 , is an ideal platform for searching for these emergent quantum phenomena. [3] Here R represents a rare-earth element, alkali metal or alkaline-earth metal; T is the transition metal (V, Cr, Mn, Fe, Co, etc. ), and X is Sn, Ge or Ga.…”

Toward Predicting the Assembly of Modular Intermetallics from Chemical Pressure Analysis: The Interface Nucleus Approach

“…The first step in this analysis is the identification of a geometrical motif that is common to the parent structures that serves as an interface nucleus for the formation of more complex assemblies. The Laves/CaCu 5 -type structures are made possible by the epitaxial matching of kagome layers, which are realizations of a net type that is correlated with intriguing materials properties and physics. , If we examine the atomic arrangements above and below the kagome nets in the structures, a common unit can be perceived (Figure a–c): a triple stack of hexagons staggered relative to each other that encircles a pair of atoms. Among the structures, the details of the unit vary in terms of the degree of planarity of the outer hexagons and the heights of the central atoms, but the commonality of this unit to the structures allows for a smooth transition between the Laves phase and CaCu 5 -type domains in the PuNi 3 type and other Laves/CaCu 5 -type intergrowths.…”

Enhanced anomalous Hall effect in kagome magnet YbMn6Sn6 with intermediate-valence ytterbium

“…Kagome magnets have been a subject of significant interest in condensed matter physics due to their unique combination of a nontrivial geometric lattice and strong electron correlation. [1,2] The kagome lattice comprises corner-sharing triangles, which naturally lead to geometric frustration and a topological band structure, characterized by the Dirac cone and flat band. These distinctive structures in both real and reciprocal spaces make the kagome materials an intriguing platform for exploring topological states and phenomena, including quantum spin liquid [3] and the long-pursued hightemperature quantum anomalous Hall effect.…”