Thermoelectrics of interacting nanosystems - Exploiting fermion-parity superselection instead of time-reversal symmetry

The electronic heat current through quantum dots with strong onsite Coulomb interaction can show surprising features of attractive interaction. This is manifested prominently at the electron-hole symmetric point, where, in systems with attractive interaction, a two-particle resonance would occur. One well-known example for this is the Seebeck thermopower in quantum dots, featuring a sign-change at this point, which is standardly interpreted as crossover between two Coulomb resonances. This shows that even the well-studied stationary, linear thermoelectric response of quantum dot systems is still not fully understood.
In this presentation, I will show that a recently discovered duality relation for fermionic systems [1] -- deriving from the fundamental fermion-parity superselection principle -- provides new insights into thermoelectric transport, both in the stationary regime [2] as well as for transient charge and heat currents [1,3]. Importantly, these insights do not rely on relations imposed by time-reversal symmetry, in contrast to the famous Onsager relations and various fluctuation relations in counting statistics. As such, the duality can be combined with a traditional analysis of thermoelectric transport in a fruitful way, and it is equally applicable to nonlinear response without requiring generalizations. Furthermore, one of its assets is that it naturally explains features of attractive interaction, via a mapping to a dual model.
The results that I will present show that next to time-reversal symmetry, the duality imposes equally important symmetry restrictions on thermoelectric transport. It is therefore also expected to simplify computations and to clarify the physical understanding for the thermoelectric response of more complex systems than the discussed quantum dot.
[1] J. Schulenborg et al.: Phys. Rev. B 93, 081411(R) (2016)
[2] J. Schulenborg et al.: arXiv:1711.01223 (2017)
[3] J. Vanherck et al.: Phys. Status Solidi B 254, 1600614 (2017)