Seminar by Habib Rostami (Nov. 5th 10:00)

Place and time: Friday November 5th at 10:00, Oddi 206

Speaker: Habib Rostami

Title: Strain physics in 2D materials: pseudo gauge field, piezoelectricity and acoustoelectric

Abstract: In the context of applied physics, we are always interested in controlling and modifying the intrinsic electronic properties of electronic systems. For instance, we can use electric and magnetic fields for this purpose. However, mechanical deformation is another external field that is not as common as electric and magnetic fields. Two-dimensional van der Walls layered materials such as graphene and transition metal dichalcogenides (TMDs) show remarkable elastic properties with strong in-plane Yang modulus and weak bending rigidity. Accordingly, they provide a promising platform for flexible electronics, optoelectronic and acousto-optic devices. I will review the manifestation of a fictitious (pseudo) gauge field in 2D materials owing to the lattice deformation. Pseudo gauge field results in an ultra-strong pseudo magnetic field preserving the time-reversal symmetry and leading to the flat-band (Landau level) formation. I will discuss strain-induced electric polarization due to the piezoelectric effect related to a topological quantity known as the valley Chern number in inversion broken TMDs. I will talk about highly efficient exciton drift mechanism in single-layer TMD owing to the strain-induced deformation potential, the built-in piezoelectric field and the pseudo magnetic field. I will present acoustogalvanic effect as a rectification process of propagating pseudo electromagnetic field (sound wave) in 2D and 3D Dirac materials. I will discuss a transverse acoustoelectric current due to a pseudo gauge field that can propagate transverse to sound propagation.