Onset of multifractality in a ferromagnetic nodal line semimetal

The ferromagnet Fe3GeTe2 is predicted to have large Berry curvature due to its classification as a nodal line semi metal. Indeed, it shows an extremely large anomalous Hall effect [1] as well as a large anomalous Nernst angle [2]. We have investigated it using scanning tunneling microscopy (STM) and spectroscopic mapping. We find that it has a sharply suppressed density of states at the Fermi energy at low temperatures. We further find the signature of multifractality in the spatial fluctuations of the density of states that onset with decreasing temperatures and peaks at the Fermi energy. We discuss possible implications our observations have for the nodal line state.

[1] K. Kim et al. Large anomalous Hall current induced by topological nodal lines in a ferromagnetic van der Waals semimetal. Nature Material 17, 794 (2018).

[2] Jinsong Xu et al. Large Anomalous Nernst Effect in a van der Waals Ferromagnet Fe3GeTe2, Nano Letters 19, 8250 (2019).