Category Archives: Reports

Report on Green’s function methods: the next generation

Objectives:

The main objective of the workshop “Green’s function methods: the next generation”, arrived at its 4-th edition, is to bring together an interdisciplinary audience of researchers dealing with Green’s functions methods and electron correlation. Both fundamental developments and high-end applications are targeted, together with discussions on numerical implementations and their current limitations.

Green’s functions have always played a prominent role in many-body physics. In particular the one-body Green’s function (GF) delivers a wealth of information about a physical system, such as ground-state energy, excitation energies, densities and other measurable quantities. Therefore the development of approximate methods to calculate the one-body GF 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 GFs. A very popular class of methods is based on the iterative solution of an integral equation for the GF 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 photo-emission 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 GF. A new wave of original ideas, understanding, and solutions, has pervaded the field and was represented in the present workshop.

Continue reading Report on Green’s function methods: the next generation

What about U in nanoscale systems?

Workshop Report
What about U in nanoscale systems?

ZCAM/BIFI, Zaragoza, Spain, May 21-24 2019

Organizers: David Jacob (UPV/EHU, San Sebastian), Massimo Capone (SISSA, Trieste), Silke Biermann (Ecole Polytechnique, Paris)

Local Organizers: Beatriz Antoli, Adrian Velazquez-Campoy (ZCAM, BIFI, Zaragoza)

The Workshop “What about U in nanoscale systems?” took place at the CECAM node in Zaragoza from May 21 to May 24 2019. It followed the format of previous What about U editions, bringing together colleagues from different communities (including experimentalists) and providing ample discussion time. The new aspect this year was the focus on nanoscale systems, while also general aspects of correlations found their place. Continue reading What about U in nanoscale systems?

Workshop on Advances in Electron Spectroscopy – Experiment and Theory, April 14-17, 2019, Dresden

The workshop aimed at bringing together experimentalists and theorists dealing with electronic structure investigations in correlated materials. Strongly correlated materials are notoriously difficult to describe theoretically due to the competing energy scales and emerging phenomena (like the Kondo effect) coming into play while at the same time experiments can provide a wealth of results whose interpretation often proves overwhelmingly challenging. It is therefore pivotal to bring together physicists investigating such materials theoretically or experimentally, to provide a common platform for discussions and encourage mutual insight into problems and results. This workshop aimed at exactly such an information exchange. Experimentally, recent advances in angle- and spin-resolved photoemission spectroscopy and scanning tunneling spectroscopy are leading examples for providing information about the materials’ electronic structure while cutting-edge density functional theory and dynamical mean field theory have developed into powerful tools for electronic structure calculations. Strongly correlated materials of interest ranged from transition metal compounds to f-electron systems. Of particular interest were also topological materials. Continue reading Workshop on Advances in Electron Spectroscopy – Experiment and Theory, April 14-17, 2019, Dresden

Developing High-Dimensional Potential Energy Surfaces: From the Gas Phase to Materials

Workshop Göttingen 2019

The workshop took place in April 2019 in Göttingen and brought together leading researchers who develop and apply machine learning methods with the common goal of determining the fundamental properties of “small” molecules, biomolecules, and materials. These properties include high-dimensional potential energy surfaces, atomic densities, and molecular properties, such as dipole moments and polarizabilities. Communities in the areas of materials, biomolecules, gas-phase molecules and complexes have formed over the past ten or so years and a major objective of the workshop was to bring these communities together to hear and learn from each other’s experience.

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15th ETSF Young Researchers’ Meeting

In 2018, the ​ ETSF Young Researchers’ Meeting​ took place in Hamburg, Germany. The hottest summer in the history of Hamburg, the well prepared Center for Free Electron Laser Science (CFEL) and more than sixty motivated researcher built the perfect frame
for a stimulating week full of science.

The Young Researchers’ Meeting (YRM) of the European Theoretical Spectroscopy Facility (ETSF) is an annual conference organized and attended exclusively by researchers without permanent position that work on state-of-the-art theoretical and computational methods for the study of electronic and optical properties of materials.

YRM is the place to present your work in progress, come up with new ideas and learn about others’ work in a ​ friendly and open​ ​ atmosphere​. Master students, PhD students as well as young post-docs from all over Europe came together and discussed latest
advances in their fields. This year, talks at the YRM were 20 minutes, including 5 minutes of discussion. This gave everyone enough time to communicate his or her findings and receive feedback from other participants.

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5th TYC Energy Workshop: From Atoms to Applications

The Thomas Young Centre (TYC) held their 5th Energy workshop, entitled “From Atoms to Applications” from the 25th to the 27th of July 2018 at the Department of Chemistry in University College London. The meeting was focussed on the evolution of computational materials design, specifically for Energy Materials. The aim of the workshop was to showcase the latest advances in computational materials design and to promote discussion and debate on bridging theory and experiment. We had a range of excellent speakers on the side of theory and of experiment, and it was clear from the discussions after talks and at the coffee breaks and lunches that the combination of theory and experiment is alive and thriving. The programme featured invited talks from established leaders in the field and from emerging early career researchers in the area. We scheduled 15 minutes for questions after every presentation, and this prompted lively discussion and debate. We had 99 attendees ranging from established academics, to PDRAs, PhD students and even Undergraduate students, with representation by Senior Editors from Nature and Nature Materials. The workshop featured diverse energy applications such as oxide and proton conducting fuel cells, photocatalysis, photovoltaics, LEDs, catalysis, solid state batteries, organic electronics and amorphous oxides semiconductors.

Read the full report here.

Report: CECAM / PSI-K Workshop Bremen on Correlated electron physics beyond the Hubbard model

CECAM Report

PROGRAM CEP

Organizers: Tim O. Wehling (Bremen), Thomas Frauenheim (Bremen), Silke Biermann (Palaiseau Cedex), Johannes Lischner (London), Nikolay Prokofiev (Amherst, Massachusetts), Malte Schüler (Bremen), Andrew Millis (New York)

Venue: University of Bremen, Bremen Center for Computational Materials Science (BCCMS), Germany, 8th until 12th of October 2018

Sponsors: University of Bremen (BCCMS), Psi-k, DFG, CECAM

Electrons in real materials are subject to Coulomb interaction among each other. This interaction is long-ranged, gives rise to correlation effects, and often poses fundamental problems in ab initio simulations of real materials. A nowadays commonly used ab initio approach for strongly correlated materials is the augmentation of density functional (DFT) based methods with many-body treatments of the Hubbard model, such as the combination of DFT and dynamical mean field theory [1]. This approach, however, neglects all correlation effects stemming from non-local Coulomb interaction, since the Hubbard model only includes the on-site part of the interaction. Combining more sophisticated diagrammatic ab initio methods (GW) with methods and models which contain the long-range contributions of the interaction (EDMFT) [2] alleviates these problems in part but comes with the introduction of further approximations. Assessing the quality of such approaches is currently hampered by the fact that even the extended Hubbard model, which is the minimal many-body model capturing explicitly non-local interactions, is at best partially understood. Continue reading Report: CECAM / PSI-K Workshop Bremen on Correlated electron physics beyond the Hubbard model

SCIENTIFIC REPORT ON “HOW EXCITING! WORKSHOP ON EXCITATIONS IN SOLIDS HUMBOLDT-UNIVERSITÄT ZU BERLIN”, BERLIN, GERMANY, JULY 31 – AUGUST 9, 2018

The fourth Berlin edition of the “HoW exciting! Workshop on excitations in solids” took place in the Campus Adlershof of the Humboldt-Universität zu Berlin between July 31st to August 9th, 2018. Excitations in solids, which were the core topic of the workshop, are among the most exciting phenomena in condensed-matter physics. In this context, the electronic-structure approach provided by density-functional theory (DFT) is only the first level in a hierarchical set of models which are needed to quantitatively describe and understand these phenomena in real materials. The main goal of the “HoW exciting! Workshop on excitations in solids” was to address these issues and to establish a robust relationship between the most recent advances in theoretical and computational methods and the different domains of applicability with respect to experiments. Specifically, in this workshop the state-of-the-art of theoretical and computational approaches to describe different kinds of excitations (optical, magnetic, vibrational, etc.) in solid-state materials were presented. Future perspectives of these methodologies and their applications in different research fields were discussed and new connections between theoretical and experimental groups, who are investigating excitations in materials from different perspectives were established. The main topics spanned the whole range of first-principles methods for excitation processes in solids, including electronic excitations, electron-phonon coupling, core-excitations, and non-equilibrium processes. Continue reading SCIENTIFIC REPORT ON “HOW EXCITING! WORKSHOP ON EXCITATIONS IN SOLIDS HUMBOLDT-UNIVERSITÄT ZU BERLIN”, BERLIN, GERMANY, JULY 31 – AUGUST 9, 2018

Physics by the Lake Workshop

The psi-k sponsored Physics by the Lake Workshop in Theoretical Condensed Matter ran in Cumberland Lodge, Windsor UK from July 30th through August 10th 2018

The course lecturers at the meeting were Sam Carr, Edward McCann, Richard Blythe, Chris Hooley, Martin Lueders, Andrew Fisher, Bartek Waclaw, Buddhapriya Chakrabarti, with technical demonstrators Raul Santos and Miriam Marques

Seminar speakers were  Graeme Ackland, Mike Payne, Julie Staunton, Raul Santos Alexandre Zagoskin and Mike Gunn

38 students attended

Lecture notes and attendance lists are available to psi-K members .https://www2.ph.ed.ac.uk/~gja/PBTL_2018_Notes.pdf Continue reading Physics by the Lake Workshop

Progresses in NonEquilibrium Green’s Functions VII

With the advent of nanoscale physics and ultrafast lasers it is now possible to directly probe real-time the correlated motion of electrons and nuclei in excited quantum states. In addition, the intensity and profile of the laser field can be tuned to control and manipulate the opto-electronic properties of a wide range of molecules and materials. All these progresses have opened new fields of research like, e.g., molecular transport, nanoelectronics, atto-physics/chemistry, nonequilibrium phase transitions, ultracold atomic gases, optimal control theory, etc.

Experiments are usually carried on large molecules, biological systems and nanostructures whose peculiar dynamical properties are inevitably linked to their atomistic structure. Thus, an ab-initio, time-dependent and quantum-mechanical approach is required for reliable calculations. The aim of this workshop was to gather together many of the most prominent theoretical and experimental scientists to advance our fundamental understanding of matter under extreme nonequilibrium conditions. Particular emphasis was given to many-body methods like Nonequilibrium Green’s Functions Theory (NEGF) and how to combine NEGF with ab initio methods like Density Functional Theory.

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