A twist for electronic and caloritronic nanoswitches*

Graphene twistronics, the study of how rotational mismatch between the layers of a vertically stacked structure affects its electronic properties, has opened up a realm of striking quantum phenomena since the discovery of the graphene magic angle. The miracle of twistronics has successfully unlocked phenomena such as Mott insulating phase, unconventional superconductivity, and quantized anomalous Hall effect with potential innovations in the fabrication of novel nanodevices, i.e. spintronics,  quantum bits, and phononic devices. 

In the present study, we computationally investigated both electronic and thermal transport properties of junctions based on Zigzag Graphene Nano-Ribbon (ZGNR) and twisted rectangular benzenoids [6,3] flake in both AA and AB-stacking configurations.  Our work demonstrated that AA-devices represent tuning from low conductance OFF-state for θ ≥ 2.2^◦ to high conductance ON-state for θ ≤ 4.4^◦. The AB-device remains at ON-state for all twisting values. Our analysis showed that the enabled switching is attributable to the formation of strong p_z−p_z interlayer interaction for lower rotational angles, enhancing the electron trapping at the top flake. Moreover, AA-devices exhibit a reduction in the energy gap as a function of θ, the semiconductor AA-1.1^◦ turns metallic at AA-6.6^◦. Surprisingly, the thermolectric calculations suggested that the twist between the ZGNR and flake could effectively engineer the heat flow through the AA-devices. Increased ZGNR lattice mismatch reduces the heat conductivity and then the Seebeck effect of AA-devices. This exciting phenomenon might be prosperous for emerging “twist caloritronics” in the future.