Using ab-initio method and ballistic transport model, we study electron and phonon energy dispersion relations of monolayer transition-metal dichalcogenides: MoS2, MoSe2, WS2, and WSe2. Their electron and heat transports as well as their thermoelectric properties are also studied under linear response regime with different doping types, crystal orientations, and temperatures. Our results show that electron and phonon transports are not very sensitive to crystal orientations because the differences between group velocity and transmission of these carriers along different transport directions are not significant. Furthermore, as temperature increases, first peak values of thermoelectric figure of merit (ZT1st peak) increase linearly except for monolayer n-type WSe2/MoSe2 and p-type WS2, which have higher increasing rates when temperature is high due to the electron transport contribution from an additional valley. Among these various conditions, the results show that all monolayers have similar ZT1st peak at low temperatures below 100 K, and p-type monolayer MoS2 has the largest ZT1st peak at room temperature while n-type WSe2 has the largest ZT1st peak at high temperatures.

Electronic spin transport through (CpFeCpV) n multidecker wire sandwiched between magnetic nickel (Ni) electrodes is simulated in the linear response regime based on DFT. We studied the effects of the molecule−electrode contact and molecule wire length on its spin filter behavior. The amplitude and the sign of the spin filter efficiency can be manipulated by choosing the contact condition (e.g., anchoring groups, absorbing positions on Ni electrodes surface). The performance of the spin filter can be further manipulated by adjusting the length of the molecule wire. Various ways to realize nearly perfect spin-filter are illustrated.

The electronic transport and photoelectric properties of hydrogenated borophene B4H4, which was realized in a recent experiment by Nishino, et al. [J. Am. Chem. Soc. 139, 13761 (2017)], are systematically investigated using the density functional theory and non-equilibrium Green's function methods. We find that B4H4 exhibits a perfect current-limiting effect and has high (along the zigzag direction) and low (along the armchair one) optional levels due to its strong electrical anisotropy. Moreover, B4H4 can generate sizable photocurrents under illumination, with strong photoelectronic response to blue/green light along the zigzag/armchair direction. Our work demonstrates that B4H4 is promising for the applications of current limiter and photodetectors. 

We present a graphene-based photonic-crystal schematic of enhancing and steering Faraday rotation angle of graphene. This concept is counter-intuitive because the giant Faraday rotation and high transmission can be simultaneously pronounced, which is distinguished from exisitng graphene structures reported before. It is found that chemical potential can be tailored to generate a controllable giant Faraday rotation via graphene with atomic thickness. By engineering the individual component thickness in the photonic crystal, the magneto-optical performance can be significantly improved. This is of fundamental importance in a wide range of magneto-optical applications, simply because the Faraday rotation makes sense only when the transmittivity is decently high. V