Evidence for two-dimensional correlated hopping in arrays of Ge/Si quantum dots

Abstract

We report an analysis of a two-dimensional variable-range hopping conductance in doped and gated Ge/Si heterostructures with arrays of Ge quantum dots. We found that the conductivity $\ensuremath{\sigma}$ versus temperature T follows the Efros-Shklovskii behavior $\ensuremath{\sigma}={\ensuremath{\sigma}}_{0}\mathrm{exp}[\ensuremath{-}{(T}_{0}{/T)}^{1/2}]$ with the temperature-independent prefactor ${\ensuremath{\sigma}}_{0}\ensuremath{\sim}{e}^{2}/h.$ A strong reduction of the measured value of the characteristic temperature ${T}_{0}$ from that calculated for single-particle hopping was observed. The data provide evidence for interaction-driven many-electron excitations in dense arrays of quantum dots.