We study electron transport through an Aharonov-Bohm ͑AB͒ interferometer with a noninteracting quantum dot in each of its arms. Both a magnetic flux threading through the AB ring and the Rashba spin-orbit ͑SO͒ interaction inside the two dots are taken into account. Due to the existence of the SO interaction, the electrons flowing through different arms of the AB ring will acquire a spin-dependent phase factor in the tunnel-coupling strengths. This phase factor, as well as the influence of the magnetic flux, will induce various interesting interference phenomena. We show that the conductance and the local density of states can become spin polarized by tuning the magnetic flux and the Rashba interaction strength. Under certain circumstances, a pure spin-up or spin-down conductance can be obtained when a spin-unpolarized current is injected from the external leads. Therefore, the electron spin can be manipulated by adjusting the Rashba spin-orbit strength and the structure parameters.

We study the coexistence of the spin-polarized current and the spin accumulation in a three-terminal quantum ring structure, in which two quantum dots (QDs) are inserted in one arm of the ring and the Rashba spin-orbit interaction (RSOI) exists in the other. We find that by properly adjusting the applied voltages in the three leads, the RSOI-induced phase factor and the parameters relevant to the QDs, the spin-polarization efficiency in the leads can achieve either 100% or infinite, and the electrons of the same or different spin directions can accumulate in the two dots, respectively. The manipulation of the electron spin in the present device relies on the RSOI and the electric fields, thus making it realizable with the currently existing technologies.

Enhanced spin figure of merit in a Rashba quantum dot ring connected to ferromagnetic leadsWe propose a pure thermoelectric spin generator based on a Rashba quantum dot molecular junction by using the temperature difference instead of the usual voltage bias difference. A magnetic flux penetrating through the device is also considered. The spin Seebeck coefficient S S and the spin figure of merit Z S T of the molecular junction are calculated in terms of the Green's function formalism and the equation of motion (EOM) technique. It is found that a pure spin-up (spin-down) Seebeck coefficient can be generated by the coaction of the magnetic flux and the Rashba spin-orbit (RSO) interaction.

We theoretically study the heat generation in a quantum dot (QD) connected simultaneously to two reservoirs and a local phonon bath. We find that driven solely by an external thermal bias, the resonant tunneling electrons can absorb heat from the phonon bath to the QD that are held at the same temperature. This QD refrigerator also works well under the thermoelectric effect. At room temperature and large thermal bias, the magnitude of the heat current density is on the order of nW/cm2 in typical Ge/Si QD, of which the dot diameter is 40 nm with phonon frequency 5 × 1013 rad/s.

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Based on nonequilibrium Green's functions (NGF) and density-functional theory (DFT), we investigate the magnetotransport properties and magnetothermoelectric effects in zigzag graphene nanoribbons (ZGNRs) with non-magnetic doping on the double ribbon edges. One of the carbon atoms without hydrogen saturation in each ribbon edge is replaced by one boron (B) or one nitrogen (N) atom. Compared with boron-boron (BB) and nitrogen-nitrogen (NN) double-edge doping, the boronnitrogen (BN) double-edge doping induces a perfect spin-filter effect with 100% negative spin polarization at the Fermi level. Moreover, we find that the thermoelectric effect can be enhanced by the double-edge doping. Interestingly, the spin Seebeck effect in NN-and BN-doped ZGNRs becomes comparable with the charge Seebeck effect and even larger than it. These results originate from the spin-dependent transmission node near the Fermi level induced by the non-magnetic doping. These findings strongly suggest that the double-edge-doped ZGNRs are promising materials for spintronics and thermo-spintronics.

The traditional driving waveform of the electrowetting display (EWD) has many disadvantages, such as the large oscillation of the target grayscale aperture ratio and a long time for achieving grayscale. Therefore, a driving waveform based on the exponential function was proposed in this study. First, the maximum driving voltage value of 30 V was obtained by testing the hysteresis curve of the EWD pixel unit. Secondly, the influence of the time constant on the driving waveform was analyzed, and the optimal time constant of the exponential function was designed by testing the performance of the aperture ratio. Lastly, an EWD panel was used to test the driving effect of the exponential-function-driving waveform. The experimental results showed that a stable grayscale and a short driving time could be realized when the appropriate time constant value was designed for driving EWDs. The aperture ratio oscillation range of the gray scale could be reduced within 0.95%, and the driving time of a stable grayscale was reduced by 30% compared with the traditional driving waveform.

The interplay between the Fano and Rashba spin-orbit (RSO) effects in an Aharonov-Bohm (AB) interferometer containing two noninteracting quantum dots (QDs) in each of its arms is studied by employing the Green’s function equation of motion. When electrons flow through the upper and lower arms of the interferometer, the RSO interaction in the QDs induces a spin-dependent phase factor in the linewidth matrix elements. By the co-action of this phase factor and the magnetic flux penetrating the AB ring, an interesting spin-dependent Fano effect will arise. It is found that the Fano line shapes of the two spin components in the conductance spectra can be tuned either synchronously or individually with the help of the structure parameters relevant to the RSO coupling strength, magnetic flux, and the structure configuration. We focus our attention on the manipulation of the swap operation of the resonances centered at the bonding and antibonding energies, spin-flip processes, and the broadening of the resonances, which might have practical applications in spintronics devices. We also find that both the broadening of the resonances and the spin polarization efficiency can be controlled in terms of the dot-lead coupling strength.