Insulating nature of strongly correlated massless Dirac fermions in an organic crystal

TL;DR

This study investigates how interactions among massless Dirac fermions in an organic crystal influence charge transport, revealing insulating behavior driven by Coulomb interactions and supporting theoretical predictions of edge states.

Contribution

It provides experimental evidence of Coulomb interaction effects on Dirac fermions and observes vanishing gaps consistent with non-topological edge states.

Findings

Resistivity upturn at low temperatures is robust and pressure-independent.

Enhanced resistivity upturn near charge-ordering critical pressure.

Evidence supports the role of Coulomb interactions and edge states in insulating behavior.

Abstract

Through resistivity measurements of an organic crystal hosting massless Dirac fermions with a charge-ordering instability, we reveal the effect of interactions among Dirac fermions on the charge transport. A low-temperature resistivity upturn appears robustly irrespectively of pressure and is enhanced while approaching the critical pressure of charge ordering, indicating that the insulating behavior originates from short-range Coulomb interactions. Observation of apparently vanishing gap in the charge-ordered phase accords with the theoretical prediction of the non-topological edge states.