Evidence of Mott Insulator with Thermally Induced Melting Behavior in Kagome Compound Nb3Cl8

TL;DR

This study provides transport evidence for Mott insulating behavior in Nb3Cl8, a layered kagome compound, revealing thermally induced melting of the insulating state and highlighting its potential for exploring correlated quantum phenomena.

Contribution

It offers the first systematic transport characterization of Nb3Cl8, confirming its Mott insulator nature and temperature-dependent gap behavior, advancing understanding of kagome-based correlated materials.

Findings

Nb3Cl8 exhibits bipolar semiconducting behavior with a Fermi level near the conduction band.

The energy gap decreases from 1.10 eV at 100 K to 0.63 eV at 300 K.

The insulating state shows thermally induced melting consistent with Mott insulator theory.

Abstract

The kagome lattice provides a playground to explore novel correlated quantum states due to the presence of flat bands in its electronic structure. Recently discovered layered kagome compound Nb3Cl8 has been proposed as a Mott insulator coming from the half-filled flat band. Here we have carried out systematic transport study to uncover the evidence of Mott insulator in Nb3Cl8 thin flakes. Bipolar semiconducting property with Fermi level close to conduction band has been revealed. We have further probed the chemical potential of Nb3Cl8 by tracing the charge neutrality point of the monolayer graphene proximate to Nb3Cl8. The gap of Nb3Cl8 flakes is approximately 1.10 eV at 100 K and shows pronounced temperature dependence, decreasing substantially with increasing temperature to ~0.63 eV at 300 K. The melting behavior of the gapped state is in consistent with theoretically proposed Mott insulator in Nb3Cl8. Our work has demonstrated Nb3Cl8 as a promising platform to study strongly correlated physics at relatively high temperature.