  The energy efficiency and power of a three-terminal thermoelectric nanodevice
are studied by considering elastic tunneling through a single quantum dot.
Facilitated by the three-terminal geometry, the nanodevice is able to generate
simultaneously two electrical powers by utilizing only one temperature bias.
These two electrical powers can add up constructively or destructively,
depending on their signs. It is demonstrated that the constructive addition
leads to the enhancement of both energy efficiency and output power for various
system parameters. In fact, such enhancement, dubbed as thermoelectric
cooperative effect, can lead to maximum efficiency and power no less than when
only one of the electrical power is harvested.
