  Studies of thermally induced transport in nanostructures provide access to an
exciting regime where fluctuations are relevant, enabling the investigation of
fundamental thermodynamic concepts and the realization of thermal energy
harvesters. We study a serial double quantum dot formed in an InAs/InP nanowire
coupled to two electron reservoirs. By means of a specially designed local
metallic joule-heater, the temperature of the phonon bath in the vicinity of
the double quantum dot can be enhanced. This results in phonon-assisted
transport, enabling the conversion of local heat into electrical power in a
nano-sized heat engine. Simultaneously, the electron temperatures of the
reservoirs are affected, resulting in conventional thermoelectric transport. By
detailed modelling and experimentally tuning the interdot coupling we
disentangle both effects. Furthermore, we show that phonon-assisted transport
gives access to the energy of excited states. Our findings demonstrate the
versatility of our design to study fluctuations and fundamental
nanothermodynamics.
