Kagome superlattice method offers new opportunity to fine-tune electronic properties of graphene

A research team has presented a novel method for tuning electronic bands in graphene. Their results, published in Physical Examination Lettersdemonstrate the potential of artificial superlattice fields to manipulate different types of band dispersions in graphene.

Conventional band patterning methods such as heterostructures, interfacial tension and alloys have limitations, especially when it comes to in situ and continuous control of the engineered band structures. The advent of van der Waals (vdW) materials, particularly graphene, has opened up new opportunities for band structure engineering through gating and moiré heterostructures, which can alter energy bands and lead to various emerging physical phenomena.

The biggest challenge is the precise control and manipulation of band structures to achieve specific electronic properties. Previous methods were less flexible and did not have the ability to actively and selectively change the dispersion properties of bands.

To address these challenges, this research introduces a paradigm-shifting method of band engineering by creating an artificial Kagome superlattice to manipulate the Dirac bands in graphene. The Kagome superlattice is designed with a large period of 80 nm, which is crucial to fold and compress various high-energy bands into a low-energy region that can be experimentally observed and manipulated.

The main innovation of the study lies in the use of a higher-order potential within the Kagome superlattice. This potential enables the reconstruction of band structures by different contributions, resulting in dispersion-selective band modulation. The researchers fabricated the artificial lattice device using standard van der Waals assembly techniques and electron beam lithography, creating a Kagome lattice pattern that acts as a local gate for the graphene.

By independently adjusting the voltage applied to the local gate and the doped silicon substrate, the researchers were able to precisely control both the strength of the artificial potential and the carrier density in the graphene. The higher-order Kagome potential allowed the researchers to observe and manipulate the redistribution of spectral weight between multiple Dirac peaks.

Furthermore, the application of a magnetic field was shown to effectively weaken the influence of the superlattice on the band structure and reactivate the intrinsic Dirac band. This finding provides another knob to control the electronic properties of the material.

In summary, the innovative approach presented in the study, which uses an artificial Kagome superlattice, offers unprecedented control over band structure engineering. This method not only expands the field’s ability to precisely manipulate electronic properties but also opens new avenues for the discovery of novel physical phenomena and materials with targeted functionalities.

The team was led by Prof. Zeng Changgan of the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS), who worked with Prof. Sheng Junyuan of Wuhan University and Prof. Francisco Guinea of ​​IMDEA Nanociencia in Spain.