The role of electron interactions in a failed insulator revealed by shot noise

In materials known as failed insulators, electrical resistivity increases as temperature decreases, yet does not diverge - a phenomenon inconsistent with single-particle theories. We investigate the origin of this behavior by measuring shot noise in nanojunctions of nitrogen-doped beta-Ta, a prototypical failed insulator. Junctions as short as 8 nanometers exhibit hot-electron shot noise, indicating strong electron interactions. We show that charge hopping mediated by these interactions explains the anomalous electronic properties. Our findings open new avenues for exploiting electron interactions in spin-orbitronic and superconducting applications of failed insulators.