Large enhancement of thermoelectric effects in a tunneling-coupled parallel DQD-AB ring attached to one normal and one superconducting lead

Abstract

We theoretically investigate the thermoelectric properties in a tunneling-coupled parallel DQD-AB ring attached to one normal and one superconducting lead. The role of the intrinsic and extrinsic parameters in improving thermoelectric properties is discussed. The peak value of figure of merit near gap edges increases with the asymmetry parameter decreasing, particularly, when asymmetry parameter is less than 0.5, the figure of merit near gap edges rapidly rises. When the interdot coupling strengh is less than the superconducting gap the thermopower spectrum presents a single-platform structure. While when the interdot coupling strengh is larger than the gap, a double-platform structure appears in thermopower spectrum. Outside the gap the peak values of figure of merit might reach the order of 102. On the basis of optimizing internal parameters the thermoelectric conversion efficiency of the device can be further improved by appropriately matching the total magnetic flux and the flux difference between two subrings.

Superior thermoelectric properties through triangular triple quantum dots (TTQD) attached to one metallic and one superconducting lead

“…In recent years, increasing attention has been paid to multiple QD hybrid systems in different coupling regimes, due to their potential applications in highly efficient nano-electronic devices and fundamental physics research. [18][19][20][21][22][23][24][25][26][27][28][29] The most common examples are double quantum dot (DQD) and triple quantum dot (TQD) systems, they not only have superior thermoelectric properties over the single quantum dot systems, but also have more means to regulate: it has been shown that the Dicke effect and level detuning play vital roles in improving the thermoelectric efficiency in parallel TQD and T-shaped DQD systems; 20,25 it has also been demonstrated that the magnitude of ZT in a parallel DQD-AB ring system can be considerably enhanced by lead coupling asymmetry, quantum interference effects and magnetic ux. [26][27][28] However, thermoelectric properties based on triangular triple quantum dot (TTQD) systems are not well explored.…”

“…The very high density of states near superconducting gap edges changes rapidly with energy, which is mainly responsible for the high thermopower and low thermal conductivity near the superconducting gap edges. However, recent studies have mainly focused on single quantum dot, 16,47 double quantum dot 28,53 and parallel coupled triple quantum dot systems, 29,45 the thermoelectric properties of TTQD coupling to one metallic-metallic and one superconducting lead have not been studied yet.…”

“…30,[48][49][50][51][52] The few recent studies on two-terminal devices have conrmed that the thermoelectric properties of QD hybrid systems coupled to one conventional lead (metallic or ferromagnetic lead) and one superconducting lead, are remarkably better than those coupled to two conventional leads. 16,28,29,45,47,53 It has been found that the thermoelectric efficiency of the former can even reach several times or even tens of times that of the latter, by comprehensively regulating the superconducting gap, interdot coupling and asymmetric parameters, which can also be additionally enhanced by the interference effect and interdot Coulomb interaction. This is mainly attributed to the unique tunnelling mechanism and high density of states distribution near superconducting gap edges.…”

Theory of Optimizing the Tunneling Probability Through a Potential Barrier by Acoustically Augmented Phonons

“…Experimental observations of strongly enhanced tunnelling between graphene bilayers and a WSe 2 barrier when the graphene bilayers are populated with carriers of opposite polarity and equal density were recently made by Williams et al [20]. The enhanced tunneling increases sharply in strength with decreasing temperature, and the tunneling current exhibits a vertical onset as a function of interlayer voltage at a temperature of 1.5 K. Large enhancements of the thermoelectric effects in a tunnellingcoupled parallel DQD-AB ring (refer [21]) attached to one normal and one superconducting lead have been theoretically investigated by Hui et al [22]. Vysotskii et al [23] presented the possibility of forming and using of correlated coherent states for time-dependent interaction of low-energy protons with crystals or individual lithium molecules, which showed that these self-similar processes provide conditions for efficient nuclear fusion and that they are impossible in "standard" accelerator fusion at high energies.…”