Dirac fermions in borophene (1702.00592v1)

Abstract: Honeycomb structures of group IV elements can host massless Dirac fermions with non-trivial Berry phases. Their potential for electronic applications has attracted great interest and spurred a broad search for new Dirac materials especially in monolayer structures. We present a detailed investigation of the \beta 12 boron sheet, which is a borophene structure that can form spontaneously on a Ag(111) surface. Our tight-binding analysis revealed that the lattice of the \beta 12-sheet could be decomposed into two triangular sublattices in a way similar to that for a honeycomb lattice, thereby hosting Dirac cones. Furthermore, each Dirac cone could be split by introducing periodic perturbations representing overlayer-substrate interactions. These unusual electronic structures were confirmed by angle-resolved photoemission spectroscopy and validated by first-principles calculations. Our results suggest monolayer boron as a new platform for realizing novel high-speed low-dissipation devices.

• The paper demonstrates that the β12 boron sheet forms a honeycomb-like structure capable of hosting Dirac fermions, verified using both theoretical and experimental methods.
• Utilizing a tight-binding model, the authors decompose the borophene lattice into two triangular sublattices, leading to the observation of distinct Dirac cone splitting due to substrate interactions.
• The study highlights the potential of borophene for advanced electronic and quantum device applications by enabling tunable high-speed, low-dissipative charge transport.

Dirac Fermions in Borophene: A Detailed Analysis

The paper under examination presents a comprehensive paper on the electronic properties of the $\beta_{12}$ boron sheet, commonly referred to as borophene, deposited on an Ag(111) substrate. The authors employ both theoretical computations and experimental techniques to elucidate the electronic structure of this novel two-dimensional material. Their key finding is the realization that the borophene exhibits a honeycomb-like electronic structure capable of hosting Dirac fermions, similar to other well-known 2D materials such as graphene, but achieved through a distinct structural pathway.

Theoretical Framework and Tight-Binding Analysis

Using a tight-binding model, the authors analyze the lattice of the $\beta_{12}$-sheet, proposing that it can be decomposed into two triangular sublattices akin to the honeycomb lattice observed in graphene. This structural decomposition is significant as it predicts the presence of Dirac cones, which are a hallmark of materials that can support high-speed, low-dissipative charge carriers. Additionally, by introducing specific periodic perturbations to mimic the interaction between the boron layer and the substrate, each Dirac cone is shown to split. This novel approach to Dirac cone manipulation is a key theoretical insight provided by the paper.

Experimental Confirmation via ARPES and First-Principles Calculations

Experimentally, the theoretical predictions are confirmed using angle-resolved photoemission spectroscopy (ARPES), which reveals the electronic band structure of the borophene sheet. The ARPES measurements identify the Dirac cones and their splitting induced by the Ag(111) substrate interactions. These experimental results are complemented by first-principles calculations, which further validate the existence of massless Dirac fermions and reinforce the weak perturbative influence of the substrate.

Implications and Future Directions

The findings presented in this paper have several important implications for the development of new electronic devices. The ability of borophene to host Dirac fermions suggests it is a promising candidate for high-speed electronic applications, potentially surpassing the performance of graphene due to its unique structural and electronic properties. Furthermore, the ability to manipulate the Dirac cones through substrate interactions could open new avenues in the field of electronic band engineering, offering a pathway to design materials with tailored electronic properties.

Going forward, the research on borophene could explore the effects of different substrates and explore doping methodologies to further tune its electronic properties. Investigations into the potential for superconductivity in borophene might also yield exciting results, given its electron-dense structure. Additionally, exploring the topological aspects of borophene may reveal novel quantum phases useful for next-generation quantum computing elements. Overall, the paper offers a solid foundation for both theoretical and experimental exploration of boron-based nanoscale materials, with promising implications for future device technologies.