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 →

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? →

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 →