Piezo and flexoelectricity driven by inhomogeneous strain in 2D materials. 01/10/2020 - 30/09/2023

Abstract

Electromechanical properties play an essential role in determining the physics of dielectric solids and their practical application. Popularly, electrostriction, and the piezoelectric effect were considered to be the two main electromechanical effects that couple an applied electric field to the strain and vice versa. The coupling between polarization and strain gradients is another electromechanical phenomenon, which can be observed by bending a material. This is known as flexoelectricity, which is present in a much wider variety of materials, including non-polar dielectrics and polymers, but is only significant at small length-scales, where high strain-gradients develop. In two dimensional (2D) materials, where large strain gradients are possible, these effects are expected to be strongly enhanced. Besides, the superior elastic properties and reduced lattice symmetry makes 2D materials promising for flexoelectricity. In this proposal, by using state of the art ab initio approaches, fundamental flexoelectric properties of a wide variety of 2D materials will be investigated. Subsequently, a multiscale modeling framework that captures the influence of internal-strain gradients on the electronic and optical properties will be developed. The work proposed here will not only provide a fundamental understanding of flexoelectricity in 2D materials but will also guide the discovery of new flexible electronics.

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Understanding and tuning of light matter interactions in transition metal dichalcogenides monolayers and their heterostructures (QuantumTMDs). 01/05/2019 - 30/04/2020

Abstract

Fundamental understanding and control of quantum phenomena on unprecedented length and time scales are essential for proper development of next generation devices. Recent advances in the synthesis of atomically thin layers of van der Waals solids such as graphene, boron nitride, and transition metal dichalcogenides (TMD) open up possibilities to success, for example, in computing, information and energy technology. Related to photonics and optoelectronics applications monolayer TMDs have potential for increasing the capabilities of conventional semiconductors by broad absorption spectrum, i.e., from near-infrared to the visible region. In this proposal, we will study the light matter interactions in monolayer TMDs and their heterostructures with emphasis on strong excitonic effects, and spin- and valley-dependent properties. To this end, we will develop model Hamiltonian techniques, which in conjunction with density functional theory based calculations will provide new insight in the light matter interactions in monolayer TMDs. The overarching goal of this proposal is to achieve understanding of novel quantum phenomena in monolayer TMDs in particular how heterostructuring, defects, and strain intertwine to produce interesting physical properties. The work proposed here will lead to major advances in understating how defects, heterostructuring, and strain modify the properties of 2D materials, resulting in novel quantum phenomena.

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Research team(s)