Direct and Converse Flexoelectricity in Two-Dimensional Materials

Building on recent developments in electronic-structure methods, we define and calculate the flexoelectric response of two-dimensional (2D) materials fully from first principles. In particular, we show that the open-circuit voltage response to a flexural deformation is a fundamental linear-response property of the crystal that can be calculated within the primitive unit cell of the flat configuration. Applications to graphene, silicene, phosphorene, boron nitride, and transition-metal dichalcogenide monolayers reveal that two distinct contributions exist, respectively of purely electronic and latticemediated nature. Within the former, we identify a key metric term, consisting in the quadrupolar moment of the unperturbed charge density. We propose a simple continuum model to connect our findings with the available experimental measurements of the converse flexoelectric effect.

Automated summary

In this paper, we calculate the flexoelectric response of 2D materials fully from first principles, and identify two distinct contributions of purely electronic and lattice-mediated nature. We determine a key metric term within the former, consisting of the quadrupolar moment of the unperturbed charge density, and propose a simple continuum model to connect our findings with experimental measurements of the converse flexoelectric effect.