Flexoelectricity and deformation potential in bulk transition metal dichalcogenides

Using first-principles approaches based on density functional perturbation theory, we calculate the properties of bulk layered transition-metal dichalcogenides (TMDCs) under the applications of strain gradients. We determine the full flexoelectric tensor, demonstrating the unique properties of such anisotropic systems, and trends with metal and chalcogenide species. In addition, we quantify the role of electronic and ionic contributions, and find that the electronic, clamped-ion contributions are dominant in these materials. To make a direct comparison with experimental observables, we use our flexoelectric coefficients to determine absolute band deformation potentials. Finally, we obtain physical intuition of these results via comparison to hexagonal Boron Nitride and a rigid atom/layer model.