Thermal spin filtering, thermal spin switching and negative-differential-resistance in thermal spin currents in zigzag SiC nanoribbons.

Spin caloritronics with a combination of spintronics and thermoelectrics has potential applications in future information science and opens a new direction in the development of multi-functional materials. Based on density functional theory and the nonequilibrium Green's function method, we calculate thermal spin-dependent transport through a zigzag silicon carbide nanoribbon (ZSiCNR), which is a heterojunction consisting of a left electrode (ZSiC-2H1H) and right electrode terminated (ZSiC-1H1H) by hydrogen. Our results show that when the temperature in the left contact increases over a critical value, the thermal spin-down current increases remarkably from zero, while the thermal spin-up current remains zero in the total-temperature region, indicating that a perfect thermal spin filter together with a perfect spin switcher is obtained. Furthermore, the thermal spin current shows a negative differential resistance effect and quantum oscillation behaviors. These results suggest that the zigzag SiC nanoribbon proposed by us can be designed as a highly-efficient spin caloritronics device with multiple functionalities.

Large negative differential resistance and rectifying behaviors in isolated thiophene nanowire devices.

We design isolated molecular nanowires composed of thiophene oligomers sandwiched between two one-dimensional gold electrodes. Electronic transport through the molecular junctions with two interface geometries is studied by performing the first principles calculations based on density functional theory and nonequilibrium Green's function. The current-voltage (I-V) curves of the molecular wires display an unexpected negative differential resistance and rectifying behaviors along with the oscillation effects, different from other theoretical and experimental studies about the analogous thiophene devices. The significant difference is attributed to the design of the one-dimensional gold electrodes with large enough vacuum layer in transverse direction in order to suppress the interaction between wires. Such transport behaviors indicate that the thiophene molecular device would be an important candidate in future molecular electronics.