Electronic and optical properties of strained graphene and other strained 2D materials: a review (1611.08627v2)

Abstract: This review presents the state of the art in strain and ripple-induced effects on the electronic and optical properties of graphene. It starts by providing the crystallographic description of mechanical deformations, as well as the diffraction pattern for different kinds of representative deformation fields. Then, the focus turns to the unique elastic properties of graphene, and to how strain is produced. Thereafter, various theoretical approaches used to study the electronic properties of strained graphene are examined, discussing the advantages of each. These approaches provide a platform to describe exotic properties, such as a fractal spectrum related with quasicrystals, a mixed Dirac-Schr\"odinger behavior, emergent gravity, topological insulator states, in molecular graphene and other 2D discrete lattices. The physical consequences of strain on the optical properties are reviewed next, with a focus on the Raman spectrum. At the same time, recent advances to tune the optical conductivity of graphene by strain engineering are given, which open new paths in device applications. Finally, a brief review of strain effects in multilayered graphene and other promising 2D materials like silicene and materials based on other group-IV elements, phosphorene, dichalcogenide- and monochalcogenide-monolayers is presented, with a brief discussion of interplays among strain, thermal effects, and illumination in the latter material family.

• The paper details how strain modulates graphene’s electronic band structure and optical response through crystallographic analysis and theoretical models.
• It reveals that strain induces Dirac cone shifts, bandgap openings, and pseudomagnetic field effects, which are crucial for tuning charge carrier mobility.
• It demonstrates that strain engineering enhances anisotropic optical absorption and modulates Raman spectra, outlining future paths for nanoelectronics research.

Overview of "Electronic and Optical Properties of Strained Graphene"

This paper presents a comprehensive review of the electronic and optical properties of graphene and other two-dimensional (2D) materials under strain. The work by Naumis, Barraza-Lopez, Oliva-Leyva, and Terrones explores the crystallographic characterization of mechanical deformations in graphene, highlighting the implications of strain and ripples on its electronic structure and optical response.

Key Points in Strain Characterization

The review begins by detailing the crystallographic changes induced by strain, emphasizing diffraction patterns and elastic transformations. It discusses how graphene's unique elasticity allows it to endure significant strain, which in turn modulates its electronic band structure. The paper methodically categorizes the theoretical approaches to understanding these transformations, elucidating the mixed Dirac-Schrödinger behaviors, emergent gravity phenomena, and topological states that emerge due to strain.

Electronic Properties Under Strain

Graphene’s electronic properties, notably its charge carrier mobility, are highly sensitive to strain. The paper discusses various methodologies, including tight-binding and density-functional theory (DFT), to explore these properties. The authors highlight several strain-induced phenomena, such as the merging and shifting of Dirac cones, bandgap openings, and the local emergence of pseudomagnetic fields. These effects are critical for potential applications in electronic devices, where tailored properties of strained graphene can enhance performance.

Optical Properties and Strain Engineering

Another significant focus of the review is the alteration of graphene’s optical properties under strain. The paper explains how strain engineering can lead to anisotropic optical absorption and modified Raman spectra, which are instrumental in detecting strain effects and designing optoelectronic devices. The interplay between optical conductivity and electronic band structure provides a pathway for developing tunable optical devices.

Broader Implications and Future Research Directions

The paper speculates on the broader implications of strain engineering for 2D materials beyond graphene. It introduces exploratory insights into other materials like silicene, phosphorene, and transition metal dichalcogenides, drawing comparisons in terms of their strain-induced properties. The authors suggest future research should focus on the nano-mechanical applications and quantum phase transitions possible in these materials.

Conclusion

This review serves as an essential resource for researchers focusing on the strained properties of 2D materials. It provides detailed insights into the physical phenomena resulting from mechanical deformations, opening new avenues for technological applications in nanoelectronics and optoelectronics. Future developments may see these insights integrated into the design of next-generation electronic materials and devices, with particular emphasis on exploiting the strain-induced tunability of material properties.