CECAM

Green’s function methods: the next generation 4

Location : CECAM-HQ-EPFL, Lausanne, Switzerland
May 14, 2019 – May 17, 2019

Organisers

Francesco Sottile (Ecole Polytechnique, Palaiseau, France)
Pina Romaniello (University Paul Sabatier, France)
Arjan Berger (University Paul Sabatier, France)

 

Green functions have always played a prominent role in many-body physics. In particular one- and two-body Green’s function deliver a wealth of information about a physical system, such as ground-state energies, ionization potentials, electron affinities, spectral functions, excitation energies, absorption spectra, etc. Therefore the development of approximate methods to calculate the one-body Green’s function has been an active research topic in many-body physics since the 60’s, and many routes have been explored in order to find increasingly accurate Green’s functions.

A very popular class of methods is based on the solution of an integral equation for the one-body Green’s function containing an effective potential, the so-called self-energy, which needs to be approximated. The well-known GW approximation belongs to this class; this approximation is the method of choice for calculating band structures, but it also shows several shortcomings, such as the wrong description of satellites in photoemission spectra, in particular in so-called strongly-correlated materials. Therefore more refined levels of approximations are needed to keep the pace with the advances made in experiment. Recently much progress has been made in this direction both by going beyond standard methods and also exploring completely novel routes to calculate Green’s functions. A new wave of original ideas, understanding, and solutions, has pervaded the field in these last years

Many new developments have occurred since the last successful “Green’s function methods” workshop we held in Toulouse in June 2017. In particular the community has seen:

1) An explosive growth of papers in which Green’s functions are used within quantum chemistry. [1-3]
2) Many efforts to combine Green’s functions with other theories such as density-functional theory, reduced-density-matrix functional theory, quantum Monte Carlo, density-matrix renormalization group, etc. [4-8]

Therefore it is timely to gather these novel explorations in a workshop.

In particular we would like to answer the following questions.

1) What are the issues/problems of the cohabitation of GF and wave-function based approaches?
2) Which knowledge obtained from the one-body GF can be exported to the calculation of higher-order GF calculations? 
3) What can the “solid state physics community” learn from the “quantum chemistry community” and vice versa?
4) How the self-consistency issues are dealt with in different approaches?
5) What are the best strategies to go beyond perturbation theory (in the density, the screening, the potential)?

 

References 

[1] van Setten et al., JCTC 11, 5665 (2015)
[2] Bruneval et al. Comput. Phys. Commun. 208, 149 (2016).
[3] Li et al. PRB 97, 035108 (2018)
[4] Gunacker et al., PRB 92, 155102 (2015)
[5] di Sabatino et al., PRB 94, 115141(2016)
[6] Kananenka and Zgid JCTC 13, 5317 (2017)
[7] Nunez Fernandez and Hallberg, Frontiers in Physics 6, 1 (2018)
[8] Giesbertz et al., arXiv:1804.09921 (2018)

Argentina

Karen Hallberg (invited speaker) (Instituto Bariloche)

Austria

Karsten Held (invited speaker) (Vienna University of Technology)

Belgium

Xavier Gonze (invited speaker) (Université Catholique de Louvain)
Michiel van Setten (invited speaker) (Universite Catholique de Louvain-la-Neuve)

Finland

Marc Dvorak (Aalto University)
Patrick Rinke (invited speaker) (Aalto University)

France

Claudio Attaccalite (invited speaker) (Institut Neel CNRS/UJF, Grenoble)
Fabien Bruneval (invited speaker) (French Alternative Energies and Atomic Energy Commission (CEA) Saclay, Gif-sur-Yvette)
Pierre-Francois Loos (invited speaker) (Laboratoire de Chimie et Physique Théoriques, UMR5626, UPS CNRS.)
Valerio Olevano (invited speaker) (CNRS Institut Neel, Grenoble)
Lucia Reining (invited speaker) (CNRS, Ecole Polytechnique, Palaiseau)
Blase Xavier (invited speaker) (CNRS)

Germany

Peter E. Bloechl (invited speaker) (Clausthal University of Technology)
Alberto Marmodoro (Ludwig Maximilians Universität)
Claudia Roedl (invited speaker) (IFTO, FSU Jena)
Christian Vorwerk (invited speaker) (Humboldt University Berlin)

Italy

Peng Chen (Italian Institute of Technology)
Giovanni Onida (University of Milano, Physics department)
Davide Sangalli (invited speaker) (CNR-ISM, Uos di Montelibretti)
Gianluca Stefanucci (invited speaker) (University of Rome, Tor Vergata, Italy)
Simone Vacondio (CNR-NANO S3, Italy)

The Netherlands

Giesbertz Klaas (invited speaker) (Vrije Universiteit Amsterdam)
Gianluca Tirimbó (Eindhoven University of Technology )

Spain

Masoud Mansouri (Donostia International Physics Center)

Sweden

Edmond Febrinicko Armay (Lund University)

Switzerland

Igor Reshetnyak (EPFL)
Alexey Tal (EPFL)
Stepan Tsirkin (University of Zurich)
Marco Vanzini (EPFL)

United Kingdom

Vihar Georgiev (University of Glasgow)
Jack Wetherell (invited speaker)(University of York)

Day 1 – Tuesday 14 May, 2019
 
14:15 – 15:00  Registration

15:00 – 15:50  Presentation – Valerio Olevano

Helium atom Hylleraas exact solution as benchmark for many-body theories

15:50 – 16:20  Coffee break

16:20 – 17:10  Presentation – Lucia Reining

Effects of dynamical screening in one-and two-body Green’s functions

17:10 – 18:00  Presentation – Xavier Gonze

Quasiparticles and phonon satellites in spectral functions: zero-point motion,

Fröhlich polaron and cumulants

 
 Day 2 – Wednesday 15 May, 2019
 

 9:30 – 10:20   Presentation – Fabien Bruneval

The linearized GW density matrix

10:20 – 10:50  Coffee break

10:50 – 11:40  Presentation – Michiel van Setten

Accuracy and precision in GW calculations

11:40 – 12:30  Presentation – Pierre-François Loos

Green functions and self-consistency: an unhappy marriage?

12:30 – 14:30  Lunch
 

14:30 – 15:20  Presentation – Jack Wetherell

Correcting the GW self-screening error with a spatially local density functional

15:20 – 16:10  Presentation – Patrick Rinke

GW and beyond: core excitations, strong correlation and artificial intelligence

16:10 – 16:40  Coffee break

16:40 – 17:30  Presentation – Xavier Blase

Embedded many-body GW and Bethe-Salpeter formalisms for disordered organic systems

 
17:30 : Poster session
 
20:00 : Social dinner
 
Day 3 – Thursday 16 May, 2019
 

9:30 – 10:20    Presentation – Christian Vorwerk

All-electron Many-Body Approach to Resonant Inelastic X-ray Scattering

10:20 – 10:50  Coffee break

10:50 – 11:40  Presentation – Claudio Attaccalite

Theory of  phonon-assisted luminescence: application  to the hexagonal boron-nitride

11:40 – 12:30  Presentation – Claudia Rödl

Predicting and Engineering the Optical Properties of Semiconductors: From Laser Sources to Transparent Conductors

12:30 – 14:30  Lunch
 

14:30 – 15:20  Presentation – Davide Sangalli

Coherent and non coherent excitons dynamics

15:20 – 16:10  Presentation – Gianluca Stefanucci

First-principles NEGF approach to ultrafast electron dynamics

16:10 – 16:40  Coffee break
16:40-19:00     Poster session
 
Day 4 –Friday 17 May, 2019
 

9:30 – 10:20    Presentation – Klaas Giesbertz

Approximate energy functionals for one-body reduced density matrix functional theory from many-body perturbation theory

10:20 – 10:50  Coffee break

10:50 – 11:40 Presentation – Karen Hallberg

Calculating precise spectral densities in correlated systems

11:40 – 12:30  Presentation – Karsten Held

π-tons — the generic optical excitations of correlated systems