Conductance through a parallel-coupled double quantum dot with a side-coupled quantum dot system

Using the non-equilibrium Green’s function technique, conductance through a parallel-coupled double quantum dot (PCDQD) with a side-coupled quantum dot system is investigated. The evolution of the conductance strongly depends on the coupling between the side-coupled quantum dot and PCDQD. Moreover, the conductance as a function of the level of side-couple quantum dot is investigated. Numerical results indicate the lineshape of Fano resonance can be modulated by adjusting the interdot coupling strength.

Download Full-text

Electronic Transport Through Double Quantum Dot Coupled to Majorana Bound States and Ferromagnetic Leads

Frontiers in Physics ◽

10.3389/fphy.2020.616107 ◽

2021 ◽

Vol 8 ◽

Author(s):

Li-Wen Tang ◽

Wei-Guo Mao

Keyword(s):

Quantum Dot ◽

Coupling Strength ◽

Bound States ◽

High Efficiency ◽

Energy Levels ◽

Electrical Current ◽

Function Technique ◽

Double Quantum ◽

Majorana Bound States ◽

Double Quantum Dot

We have studied theoretically the properties of electrical current and tunnel magnetoresistance (TMR) through a serially connected double quantum dot (DQD) sandwiched between two ferromagnetic leads by using the nonequilibrium Green’s function technique. We consider that each of the DQD couples to one mode of the Majorana bound states (MBSs) formed at the ends of a topological superconductor nanowire with spin-dependent coupling strength. By adjusting the sign of the spin polarization of dot–MBS coupling strength and the arrangement of magnetic moments of the two leads, the currents’ magnitude can be effectively enhanced or suppressed. Under some conditions, a negative TMR emerges which is useful in detection of the MBSs, a research subject currently under extensive investigations. Moreover, the amplitude of the TMR can be adjusted in a large regime by variation of several system parameters, such as direct hybridization strength between the MBSs or the dots and the positions of the dots’ energy levels. Such tunable currents and TMR may also find use in high-efficiency spintronic devices or information processes.

Download Full-text

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

Journal of Nanoelectronics and Optoelectronics ◽

10.1166/jno.2021.3025 ◽

2021 ◽

Vol 16 (5) ◽

pp. 753-761

Author(s):

Jing Wang ◽

Lian-Liang Sun ◽

Feng Chi ◽

Zhen-Guo Fu

Keyword(s):

Quantum Dot ◽

Function Technique ◽

Double Quantum ◽

Thermoelectric Effect ◽

Thermoelectric Transport ◽

Zero Modes ◽

Symmetric Point ◽

Double Quantum Dot ◽

Sign Change ◽

Non Equilibrium Green’S Function

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.

Download Full-text