Thermoelectric properties of aperiodic gated graphene superlattices

Thermoelectric devices, which convert temperature differences into electric power and vice versa, have applications in refrigeration, power generation, and temperature measurements. Graphene has physical characteristics that make it attractive as a thermoelectric material, but graphene monolayers have the downside of high thermal conductivity, which greatly reduces their thermoelectric efficiency.

Molina-Valdovinos et al. investigated the transport and thermoelectric properties of gated graphene superlattices. In particular, the researchers explored aperiodicity as a way to improve the material’s thermoelectric properties. Their results suggest that aperiodic thermoelectric devices based on 2D materials could potentially push forward the relevance and impact of the technology.

They designed two thermoelectric device prototypes based on aperiodic gated graphene superlattices. For each of the devices, metallic gates were arranged according to a specific non-periodic sequence: Fibonacci for one and Thue-Morse for the other, with the applied gate voltage each corresponding to the respective Fibonacci or Thue-Morse potential profile. The researchers then use standard theoretical methods, such as Landauer-Büttiker formalism and the Cutler-Mott formula, to model the coherent quantum transport in the gated graphene superlattices.

The numerical results show that the power factor – a parameter directly related to the thermoelectric efficiency – increases significantly after nanostructuring the monolayer graphene aperiodically with electrodes. Specifically, the power factor of Thue-Morse gated graphene superlattices was two times greater than that of the periodic and the Fibonacci gated graphene superlattices.

Future work will involve studying the thermoelectric properties of 2D materials beyond graphene, such as silicene, phosphorene, and transition metal dichalcogenides.

Source: “Low-dimensional thermoelectricity in aperiodic gated graphene superlattices,” by S. Molina-Valdovinos, E. J. Guzmán, and I. Rodríguez-Vargas, Journal of Applied Physics (2020). The article can be accessed at http://doi.org/10.1063/1.5139434 .