Zhanybek Alpichshev is from the Institute of Science and Technology, Austria.

Abstract:

Lead-halide perovskites are known for their extraordinary optoelectronic properties. These properties clearly arise from the interplay between their electronic and structural characteristics, but understanding the precise nature of this interplay remains a challenge.

In this talk, I will begin by discussing the fundamental aspects of the electronic structure of lead-halide perovskites which exhibits unexpected parallels with elementary particle physics. These parallels go beyond the simple resemblance between the shapes of the electron dispersion curves, and I will proceed by describing the observation of the direct analog of the dynamical version of the so-called Schwinger Effect in lead-halide perovskites. Apart from being the first table-top demonstration of one of the most fundamental predictions of quantum field theory, this observation also holds great potential for practical infrared sensing. To illustrate, I will describe how the dynamic Schwinger effect can be used for the non-perturbative amplification of the up-conversion process in perovskites driven simultaneously by multiple optical fields.

In the second part, I will talk about using the tunneling photo-ionization to explore the much-debated local structure of perovskites, which likely holds clue to some — if not many — of their remarkable properties. Combining nonlinear optics with transport methods, we find that the cubic symmetry in the nominally symmetric MAPbBr3_3 single-crystal samples is broken due to spontaneous ferroelasticity. We reveal the domained structure of ferroelasticity in perovskites, and discover the presence of flexoelectricity at the domain boundaries, which reconciles prior conflicting observations about structural symmetry in lead-halide perovskites and has far-reaching implications for understanding photoelectricity—the foremost application of this fascinating family of materials.