Temperature dependence of the electron tunneling spectra in monolayer a-RuCl3 grown on graphite

The domination of Kitaev Ising spin coupling in a-RuCl3, a spin-orbital assisted Mott insulating compound, manifests at temperatures below approximately 120 K, rendering a-RuCl3 to be a promising candidate for Kitaev quantum spin liquid. Herein, employing scanning tunneling microscopy/spectroscopy measurements, we present our observations on the temperature-dependent electron tunneling spectra in monolayer a-RuCl3 directly grown on graphite surface. A full charge (Mott) gap at low temperature undergoes significant reduction upon warming. This transformation occurs dominantly at around 120 K, crossing the temperature from Kitaev quantum paramagnet to conventional paramagnet in a-RuCl3. Excluding any layer-dependent structural phase transitions in the bulk a-RuCl3 crystal at a comparable temperature, we believe that the short ranged Kitaev Ising spin interaction has effectively facilitated the charge-trapping in Mott-Hubbard framework through the interplay between charge and spin sectors.