Discovery of a quantum limit Chern magnet TbMn6Sn6

TL;DR

This paper reports the discovery of a topological kagome magnet, TbMn6Sn6, exhibiting quantum-limit Chern phases with Landau quantization, spin-polarized Dirac dispersion, and topological edge states, advancing understanding of topological quantum phenomena in magnetic materials.

Contribution

It introduces a new topological kagome magnet TbMn6Sn6 with atomic-scale imaging and evidence of quantum-limit Chern phases, linking topology, magnetism, and electronic structure.

Findings

Visualization of defect-free Mn-based kagome lattice.

Observation of Landau quantization and spin-polarized Dirac dispersion.

Demonstration of bulk-boundary and Berry curvature correspondence.

Abstract

The quantum level interplay between geometry, topology, and correlation is at the forefront of fundamental physics. Owing to the unusual lattice geometry and breaking of time-reversal symmetry, kagome magnets are predicted to support intrinsic Chern quantum phases. However, quantum materials hosting ideal spin-orbit coupled kagome lattices with strong out-of-plane magnetization have been lacking. Here we use scanning tunneling microscopy to discover a new topological kagome magnet TbMn6Sn6, which is close to satisfying the above criteria. We visualize its effectively defect-free purely Mn-based ferromagnetic kagome lattice with atomic resolution. Remarkably, its electronic state exhibits distinct Landau quantization upon the application of a magnetic field, and the quantized Landau fan structure features spin-polarized Dirac dispersion with a large Chern gap. We further demonstrate the bulk-boundary correspondence between the Chern gap and topological edge state, as well as the Berry curvature field correspondence of Chern gapped Dirac fermions. Our results point to the realization of a quantum-limit Chern phase in TbMn6Sn6, opening up an avenue for discovering topological quantum phenomena in the RMn6Sn6 (R = rare earth element) family with a variety of magnetic structures. Our visualization of the magnetic bulk-boundary-Berry correspondence covering real and momentum space demonstrates a proof-of-principle method revealing topological magnets.