Speaker
Description
The aim of this talk is twofold: First, to introduce the EPW code, a core module of the Quantum ESPRESSO materials simulation suite which specializes on high-accuracy calculations of electron-phonon interactions and related materials properties; Second, to describe some recent applications of EPW to the study of polarons in two-dimensional crystals and halide perovskites.
Since its creation in 2006, the EPW code has grown to become a fully-fledged tool for advanced many-body calculations of electron-phonon physics, including carrier transport and magnetotransport, superconductivity, phonon-assisted optics, polarons, and thermal band structure renormalization. Here, I will briefly introduce the EPW development team, review the structure and capabilities of EPW, and discuss ongoing developments and future directions.
As an example application of EPW, I will describe recent work on polarons. The polaron is an emergent quasiparticle consisting of an electron dressed by a cloud of virtual phonons, and is responsible for a plethora of unconventional transport and optical properties. Recent experimental investigations highlighted the importance of polarons in interesting classes of materials such as boron nitride, transition metal dichalcogenides, and halide perovskites. Here, I will discuss the structure and energetics of polarons in representative systems of these classes. In particular, I will show how phonon-induced electron localization leads to a rich variety of quasiparticles of all sizes and shapes, and raises interesting questions on our current understanding of electron dynamics in complex materials.
