Louk RADEMAKER
While the difference between insulators and metals is strictly speaking only defined at zero temperature, it has become commonplace to identify systems with a negative temperature-derivative of the resistivity (drho/dT < 0) as insulators. This is, however, misleading. In particular, sufficiently close to a metal-insulator transition a system can have drho/dT < 0 yet reach a finite zero-temperature resistivity, meaning it is actually a metal. Such ‘fake insulators’ can obscure the interpretation of Mott- and band metal-insulator transitions. Therefore, we will look into the origin of ‘fake insulator’-behavior and the role of disorder and electronic correlations. Finally, we will discuss fake insulators in recent experiments in Moiré systems including twisted bilayer graphene and transition metal dichalcogenide (TMD) bilayers.