Optimal single quantum dot heat-to-pure-spin-current converters

We delve into the conditions under which a quantum dot thermoelectric setup may be tuned to realize an optimal heat-to-pure-spin-current converter It is well known that a heat-to-pure-spin-current converter may be realized using a non-interacting quantum dot with a spin-split energy spectrum under particle hole symmetry conditions. However, with the inclusion of Coulomb interaction U, ubiquitous in typical quantum dot systems, the relevant transport physics is expected to be altered. In this work, we provide a detailed picture of thermoelectric pure spin currents at various Coulomb interaction parameters U and describe the conditions necessary for an exact cancelation of charge transport between energy levels c and their Coulomb-charged partner levels epsilon + U, so as to yield the largest terminal pure spin currents. A non-trivial aspect pointed out here is that at sufficiently large values of U (>= U-0), pure spin currents tend to optimize at points other than where the particle-hole symmetry occurs. It is also ascertained that a global maximum of pure spin current is generated at a typical value of the interaction parameter U. These optimum conditions may be easily realized using a typical gated quantum dot thermoelectric transport setup. (C) 2015 Elsevier B.V. All rights reserve