[Paper Review] A review of the electronic and optical properties of strained graphene and other similar 2D materials

Gerardo G. Naumis, Salvador Barraza‐Lopez+2 more|arXiv (Cornell University)|Nov 25, 2016

2D Materials and Applications5 citations

TL;DR

This review synthesizes current understanding of strain-induced electronic and optical modifications in graphene and related 2D materials, employing theoretical models to reveal exotic quantum phenomena such as fractal spectra, emergent gravity, and topological states. It demonstrates that strain engineering enables tunable optical conductivity and Raman responses, enabling new optoelectronic device designs.

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-Schrodinger 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.

Motivation & Objective

• To systematically analyze the impact of mechanical strain and ripples on the electronic and optical behavior of graphene and other 2D materials.
• To identify and explain exotic quantum phenomena—such as fractal energy spectra and emergent gravity—induced by strain in 2D lattices.
• To evaluate theoretical frameworks for modeling strained graphene’s electronic structure and their predictive capabilities.
• To review experimental and theoretical advances in strain-tuned optical properties, particularly Raman spectroscopy and conductivity.
• To extend insights to multilayer graphene and emerging 2D materials like silicene, phosphorene, and dichalcogenides, including strain-thermal-light interplays.

Proposed method

• Utilizes crystallographic and diffraction pattern analysis to model various deformation fields in 2D lattices.
• Applies theoretical approaches such as tight-binding models and continuum elasticity theory to describe strain effects on electronic band structure.
• Employs Dirac equation formalism with gauge field analogs to model emergent relativistic effects under strain.
• Analyzes Raman spectra as a key experimental probe for strain distribution and lattice distortion in graphene.
• Integrates optical conductivity calculations under strain to assess tunability for device applications.
• Extends models to multilayer systems and other 2D materials by incorporating layer coupling and anisotropic mechanical responses.

Experimental results

Research questions

• RQ1 How do different types of strain and ripple patterns alter the electronic band structure of graphene?
• RQ2 What theoretical frameworks best describe the emergence of fractal spectra and Dirac-Schrödinger hybrid behavior in strained 2D systems?
• RQ3 How does strain modulate the Raman spectrum and optical conductivity in graphene?
• RQ4 In what ways can strain engineering be leveraged to achieve tunable optoelectronic responses in 2D materials?
• RQ5 How do strain, thermal effects, and light illumination interact in transition metal dichalcogenide monolayers?

Key findings

• Strain in graphene induces a fractal energy spectrum analogous to quasicrystalline systems, arising from quasiperiodic lattice distortions.
• Strained graphene exhibits mixed Dirac-Schrödinger behavior, where relativistic Dirac fermions hybridize with non-relativistic Schrödinger-like states.
• Strain generates effective gauge fields that mimic gravitational potentials, leading to emergent gravity effects in 2D lattices.
• Strain engineering enables tunable optical conductivity in graphene, offering pathways for dynamic photodetector and modulator design.
• Raman spectroscopy reveals distinct strain-dependent peak shifts and broadening, serving as a reliable probe for local strain mapping.
• Multilayer graphene and 2D materials like phosphorene and dichalcogenides exhibit complex strain-thermal-light coupling effects, influencing their electronic and optical responses.