Giant current density via indirect exciton orbit overlapping in polarized nanogranular materials

Anomalous charge transport in nanogranular material (NGM), closely packed 2–4 nm diameter metal nanoparticle-carbon matrix composite, is modeled using a cluster of electron–hole pairs (super-atom) or indirect excitons produced among locally polarized composite. The observed conductivity and T−1/2 temperature dependence of its logarithm suggests variable range hopping or cotunneling via overlapping orbits among adjacent particles limited by electron–hole interaction. Further, electron–hole liquid is expected from predicted high densities of charge carriers, allowing a giant current carrying capacity. The Bose–Hubbard phase diagram and an interexciton distance shorter than the thermal de Broglie wavelength suggests the possibility of NGM as a platform for excitonic quantum condensate.