Thermoelectric Transport in a Double-Quantum-Dot Coupled to Majorana Zero Modes

Abstract

Thermoelectric transport through a double-quantum-dot (DQD) connected to the left and right leads is theoretically investigated in the framework of non-equilibrium Green’s function technique. We consider that the dots are also coupled to Majorana zero modes (MZMs) prepared at the two ends of a topological superconductor nanowire. It is found that the sign change of thermopower, which is promising in the detection of MZMs, can be realized by tuning several system’s parameters related to the MZMs, such as the coupling strength between the dots and the MZMs, the direct coupling between the MZMs, or even the magnetic flux penetrating through the structure. The above parameters also lead to significant enhancement of the thermopower and thermoelectric figure of merit (FOM), which indicates the conversion efficiency between heat and electrical energies. We also find that in this DQD system, both the thermopower and FOM are simultaneously enhanced by the MZMs around the electron-hole symmetric point, an ideal phenomenon in applications of thermoelectric effect. In addition, the thermoelectric effect is remarkably enhanced by the direct hybridization between the MZMs, which is very different from the case in single-dot structure.