Negative flat band magnetism in a spin–orbit-coupled correlated kagome magnet

Abstract

It has long been speculated that electronic flatband systems can be a fertile ground for hosting novel emergent phenomena including unconventional magnetism and superconductivity 1-14 . Here we use scanning tunnelling microscopy to elucidate the atomically resolved electronic states and their magnetic response in the kagome magnet 15-20 Co3Sn2S2. We observe a pronounced peak at the Fermi level, which is identified to arise from the kinetically frustrated kagome flatband. Increasing magnetic field up to ±8T, this state exhibits an anomalous magnetization-polarized Zeeman shift, dominated by an orbital moment in opposite to the field direction. Such negative magnetism can be understood as spin-orbit coupling induced quantum phase effects 21-25 tied to non-trivial flatband systems. We image the flatband peak, resolve the associated negative magnetism, and provide its connection to the Berry curvature field, showing that Co3Sn2S2 is a rare example of kagome magnet where the low energy physics can be dominated by the spinorbit coupled flatband. Our methodology of probing band-resolved ordering phenomena such as spin-orbit magnetism can also be applied in future experiments to elucidate other exotic phenomena including flatband superconductivity and anomalous quantum transport.

Flat Band and Hole-induced Ferromagnetism in a Novel Carbon Monolayer

“…When the NNN hopping is zero, a perfect flat band occurs with kagome lattice as shown in Fig. 4(d), which is consistent with the previous studies [35][36][37][38][39].…”

Magnetic-Field Control of Topological Electronic Response near Room Temperature in Correlated Kagome Magnets

“…Fe spins in Fe3Sn2 are separated by Sn into bilayer Kagome planes, and their magnetism and topological band structure are quasi-two-dimensional. Interestingly, similar magnetic and electronic properties have recently been discovered for other Kagome systems such as Co3Sn2S2 [10] and van der Waals metals such as Fe3GeTe2 [28,29], for which both low-dimensional ferromagnetism and anomalous Hall effect have been observed. Manipulating the mesoscopic magnetic textures in these materials can give rise to a new control of their topological properties.…”

Dirac fermions and flat bands in the ideal kagome metal FeSn

“…These promising theoretical proposals have driven and guided recent experimental efforts toward the realization and study of topological kagome metals based on binary and ternary intermetallic compounds [11][12][13][14][15][16][17][18][19][20][21][22] . At variance with other widely studied s or p orbital-based topological systems that are close to the non-interacting limit, the kagome lattice in these intermetallic materials is populated by the low-energy 3d electrons of transition metals (Fig.…”