This is the fourth session of the second season of the Mixed-Gen on-line series aimed mainly at PhD students and researchers in their first post-doc. Our goal is to continue providing a new venue for these young scientists to share their work, get expert feedback and have an opportunity to strengthen scientific relations within the CECAM community.

The general area for this session is Simulating quantum materials

To participate

If you are a PhD student or a post-doc:

Please use the Participate Tab on this page to start the application. You will have to login using your CECAM account to access the application form. If you don't have a CECAM account yet, use the register option on the top right corner of the login page...and welcome to CECAM!

If you are a more senior scientist:

Please contact the organisers and we shall process your registration.

Submission of posters

(Please note that - at least for the time being - we shall accept posters only from PhD students or researchers in their first post-doc)

After your application is accepted, you will be able to submit a poster. In the CECAM page for this event, go to “My participation” tab and click on “Add a poster”, providing title and abstract following the recommended format. On the same form you can upload your poster file in png or jpg as soon as it is ready. These formats are strict to enable showing of the poster in the Gather session. If the poster file is not ready at the moment of submitting your abstract, you can upload it later by editing your submission (Go to “My participation” tab and click three vertical dots on “Actions” column on table “My posters”). Please upload your poster as soon as possible to enable a decision from the selection committee - see below.

Please note that posters will be visible in the Gather room associated with this session until the end of the series (June 2022) unless otherwise requested.

DEADLINE FOR SUBMISSION: TEN DAYS BEFORE THE EVENT

Selection of posters

Posters will be selected by the event organisers with the support of our main speaker and experts who will take place in the poster session. 

Selection of the two talks by PhD or first year postdocs

These contributions, to be broadcasted in the Zoom webinar in the first part of the event, will be selected, after a preliminary screening by the organisers, the main speaker and guest experts, via a lottery from the posters selected for the Gather session. Please tick “No” to the question “Upgrade to talk?” in your application if you DO NOT WANT your poster to be considered for this lottery. 

THE DECISION ON THE POSTER AND THE OUTCOME OF THE LOTTERY SELECTION WILL BE COMMUNICATED ONE WEEK BEFORE THE EVENT

POSTER SUBMISSIONS BEYOND THIS DEADLINE WILL BE ACCEPTED BUT NOT CONSIDERED FOR UPGRADE TO TALK. SUBMISSION WILL BE DEFINITELY CLOSED FOUR DAYS BEFORE THE EVENT.

SESSION 4. Title and abstract of talks

Electronic structure of quantum materials with strong correlations: a dynamical mean-field theory perspective

Antoine Georges ,  Collège de France, Paris and Flatiron Institute, New York

From copper-oxide superconductors to twisted bilayer graphene and transition-metal dichalcogenides, materials with strong electronic correlations have focused enormous attention over several decades. Solid-state chemistry, new elaboration techniques and improved experimental probes are constantly providing us with examples of novel materials with surprising electronic properties.

In this lecture, I will review some salient physical aspects of strong electronic correlations. I will emphasize that the classic paradigm of solid-state physics, in which electrons form a gas of wave-like quasiparticles, must be seriously revised for strongly correlated materials. Instead, a description accounting for both atomic-like excitations in real-space and quasiparticle excitations in momentum space is required. I will review how Dynamical Mean-Field Theory (DMFT) fulfills this goal. By providing both qualitative insights and quantitative predictions, this approach has significantly advanced our understanding of materials with strong electronic correlations.

Ab initio description of strongly correlated materials: combining density functional theory and dynamical mean-field theory

Sophie Beck, Flatiron Institute, New York

The use of density functional theory (DFT) and dynamical mean field theory (DMFT) has proven successful as a combined approach for electronic structure calculations of strongly correlated materials. In this talk, I will give an overview of how the computational approach works in practice, focusing also on our recent implementation of full charge self-consistency using the community codes Quantum Espresso, Wannier90, and TRIQS. I will discuss recent advances in realistic materials modeling and present our implementation of the DFT+DMFT method in the solid_dmft software package.

Dynamical Mean Field Theory on a Quantum Computer

Jannis Ehrlich, Fraunhofer IWM

Quantum computers promise to overcome the limitations in size which prevent the simulation of large correlated systems with conventional computers. As quantum computers are still in their early stage, we chose the two-site DMFT in order to investigate their potential and current limitations. Calculations based on simulators show, that quantum computing has the potential for these applications, but a specific treatment of statistical errors is required, to ensure that singularities lift each other even when the accuracy is limited.

Anharmonic lattice dynamics from vibrational dynamical mean-field theory

Petra Shih, Timothy Berkelbach, Columbia University

We introduce vibrational dynamical mean-field theory (VDMFT) as a non-perturbative and systematically improvable method for the simulation of anharmonic lattice dynamics [1]. Inspired by DMFT, VDMFT maps the dynamics of a periodic anharmonic lattice of atoms onto those of a self-consistently defined impurity problem with local anharmonicity and coupling to a bath of harmonic oscillators. We test VDMFT on models of anharmonic optical and acoustic phonons with classical and quantum impurity solvers, and describe nonlocal anharmonicity via its cellular extension and the combination with self-consistent phonon (SCPH) theory (SCPH+VDMFT). With much fewer degrees of freedom in the impurity model than in the full supercell, we show the convergence to accurate results at affordable computational costs.

Reference

[1] Papers: P. Shih and T. Berkelbach, arXiv:2109.00028 (2021)