Dr. Sebastian Paeckel: Dr. Sebastian Paeckel is from LMU Germany and is one of the world leading experts in Tensor Network methods.

Title: Tensor network methods for open electron-phonon systems: Bipolarons in the presence of dissipation

Abstract: Studying the interplay between electrons and phonons recently has seen a remarkable revival, driven by both methodical progress, as well as fascinating new physical insights, such as the possibility of light-bipolaron induced superconductivity [1,2] or the enhancement of transport properties [3]. Here, investigating the effects of environments (dissipative, thermal, driven) coupled to the phonon system is a crucial but enormously challenging problem, which on the one hand is important to understand the validity of effective, isolated models, while on the other hand allows for tailored manipulations of the phononic state. Recently, we developed a new toolbox of tensor network methods which are designed to allow an efficient treatment of electron-phonon systems in- and out-of equilibrium as well as coupled to an environment. Exhibiting a speed-up of significantly more than an order of magnitude, we are able to implement open quantum system techniques, which previously had been way too expensive to be of proper use for studying large system sizes by means of tensor network methods.
In this talk I introduce the developed tools and give a brief overview of the current state, their potential and limitations. Furthermore, I discuss a first application, namely the effect of a dissipative environment, coupled to the Hubbard-Holstein model, putting the emphasis on a previously reported enhancement of the metallic phase.
[1]  Phys. Rev. Lett. 121, 247001 (2021)
[2]  https://doi.org/10.48550/arXiv.2203.07380
[3] Scientific Reports volume 7, 3774 (2017)

Short Bio: Sebastian did his PhD in Göttingen from 2015-2019 focussing on the development Matrix Product States (MPS) methods, in particular time evolution methods. In 2019 he had an internship at Microsoft Station Q iand studied transport through Majorana Islands. In 2020, he became a Junior Researcher Leader in LMU in Munich and started studying electron phonon systems (method development and application, also to quantum chemistry problems).