Gate-modulated thermopower of disordered nanowires: II. Variable-range hopping regime

International audienceWe study the thermopower of a disordered nanowire in the field effect transistorconfiguration. After a first paper devoted to the elastic coherent regime (Bosisio R., Fleury G.and Pichard J.-L. 2014 New J. Phys. 16 035004), we consider here the inelastic activated regimetaking place at higher temperatures. In the case where charge transport is thermally assisted byphonons (Mott Variable Range Hopping regime), we use the Miller-Abrahams random resistornetwork model as recently adapted by Jiang et al. for thermoelectric transport. This approachpreviously used to study the bulk of the nanowire impurity band is extended for studying itsedges. In this limit, we show that the typical thermopower is largely enhanced, attaining valueslarger that 10 kB/e ∼ 1 mV K−1 and exhibiting a non-trivial behaviour as a function of thetemperature. A percolation theory by Zvyagin extended to disordered nanowires allows us toaccount for the main observed edge behaviours of the thermopower