Helical Luttinger Liquid on the Edge of a Two-Dimensional Topological Antiferromagnet

A boundary helical Luttinger liquid (HLL) with broken bulk time-reversal symmetry belongs to a unique topological class that may occur in antiferromagnets (AFM). Here, we search for signatures of HLL on the edge of a recently discovered topological AFM, MnBi2Te4 even-layer. Using a scanning superconducting quantum interference device, we directly image helical edge current in the AFM ground state appearing at its charge neutral point. Such a helical edge state accompanies an insulating bulk which is topologically distinct from the ferromagnetic Chern insulator phase, as revealed in a magnetic field driven quantum phase transition. The edge conductance of the AFM order follows a power law as a function of temperature and source-drain bias which serves as strong evidence for HLL. Such HLL scaling is robust at finite fields below the quantum critical point. The observed HLL in a layered AFM semiconductor represents a highly tunable topological matter compatible with future spintronics and quantum computation.

Automated summary

We search for evidence of a boundary helical Luttinger liquid (HLL) on the edge of a recently discovered topological antiferromagnet (AFM), MnBi2Te4 even-layer, and directly image the helical edge current using a scanning superconducting quantum interference device. The observed helical edge state accompanies an insulating bulk with a topological difference from the ferromagnetic Chern insulator phase. The edge conductance of the AFM order follows a power law as a function of temperature and source-drain bias, providing strong evidence for the existence of HLL. The observed HLL is robust at finite fields below the quantum critical point. The discovery of HLL in a layered AFM semiconductor has important implications for future spintronics and quantum computation.