New approach to ab initio modelling of electron-phonon interactions in correlated materials

Correlated materials, which feature highly localized electrons and strong coupling between electrons, their spin, and atomic vibrations, are among the most mysterious and exotic of all solids. They can host states of matter ranging from high-temperature superconductivity to metal-nonmetal transitions, colossal magnetoresistance and multiferroicity. Much-needed theoretical research into these materials is nonetheless hampered by a lack of quantitative methods capable of accurately describing the electron-phonon interactions that play a critical role in determining their unique properties. In a letter just published in Physical Review Letters, a team of researchers from EPFL, Caltech and colleagues introduce an ab initio approach that allows for the quantitative calculations of such interactions. The method can be broadly applied to various families of strongly correlated materials, capturing the strong coupling of electron, spin and lattice degrees of freedom and their combined effect on electron-phonon interactions, paving the way for quantitative studies of their rich physics.

First-ever rare earth nickelate single crystals lead to first experimental evidence supporting predicted multiferroicity

Perovskites—materials with crystal structures similar to that of calcium titanium oxide—have unique properties. Rare earth nickelates such as RENiO3, for instance, are metallic at high temperatures, but insulating and magnetically ordered at low temperatures. Moreover, it has been theoretically predicted that these materials might be multiferroic, that is, featuring simultaneously occurring ferroelectric and magnetic order in the low temperature phase. While the materials have drawn much attention for potential applications in fields of research ranging from optoelectronics, to battery engineering and neuromorphic computation, crucial experimental data needed to validate theoretical predictions has been lacking because the materials are very difficult to synthesize—to date, it has not been possible to grow sizable bulk single crystals based on rare earths other than La, Pr and Nd. Now, MARVEL researchers at PSI and colleagues have successfully grown bulk single crystals of the full nickelate family while another team including former MARVEL members from the University of Geneva has used them to provide experimental evidence supporting the existence of multiferroicity in these materials.

Newly identified R-2 2D material may show promise in development of spin-layer-locking spinFETs

Today’s electronic devices rely on the electron’s negative charge to manipulate electron motion or store information. So-called spintronic devices, which would also exploit the spin of electrons for information processing and storage, may ultimately allow us to reduce energy consumption while increasing information processing capabilities, giving us multi-functional, high-speed, low-energy electronic technologies. An essential first step, however, is finding appropriate high-performance materials and integrating them into devices that allow us to control their properties well. In the paper “Gate Control of Spin-Layer-Locking FETs and Application to Monolayer LuIO,” recently published in Nano Letters, NCCR MARVEL researchers and colleagues identified lutetium oxide iodide (LuIO) as just such a material. They studied how to control its properties with electric gates—simulating for the first time ever the effect of electronic doping—and provided practical guidelines for building and operating associated devices from such material.

Common workflows for computing material properties with various quantum engines

Using electronic-structure simulations based on density-functional theory to predict material properties has become routine, thanks at least in part to an ever-widening choice of increasingly robust simulation packages. This wide selection of codes and methods allows for cross-verification, useful in ascertaining accuracy and reliability. But the wide range of methods, algorithms and paradigms available make it difficult for non-experts to select or efficiently use any one for a given task. In the paper “Common workflows for computing material properties using different quantum engines,” published today in npj Computational Materials, a team led by researchers in NCCR MARVEL and in the MaX CoE  shows how the development of common interfaces for workflows that automatically compute material properties can address these challenges and demonstrate the approach with an implementation involving 11 different simulation codes. Also thanks to the use of the AiiDA workflow engine, they guarantee reproducibility of the simulations, simplify interoperability and cross-verification, and open up the use of quantum engines to a wider range of researchers.   

OPTIMADE API enables seamless access and interoperability across materials databases

More than 30 research institutions including NCCR MARVEL have come together to form the Open Databases Integration for Materials Design consortium and develop an API specification enabling seamless access and interoperability among materials databases. The paper “OPTIMADE, an API for exchanging materials data,” published today in Nature Research’s journal Scientific Data, presents the OPTIMADE API specification, illustrates its use and discusses future prospects and ongoing development. 

MARVEL Junior Seminar — October 2021

The MARVEL Junior Seminar series is continuing in videoconferencing mode. We are therefore pleased to propose the 44th MARVEL Junior Seminar: Tommaso Chiarotti (EPFL) and Tomáš Bzdušek (PSI/UZH) will present their research. The seminar will be chaired by Sara Fiore (ETHZ).

MARVEL Distinguished Lecture — John Perdew

The 27th NCCR MARVEL Distinguished Lecture will be given by Prof. John Perdew, Professor of physics and chemistry at Temple University on "More-predictive density functionals, symmetry breaking, and strong correlation"

MARVEL Junior Seminar — December 2024

The MARVEL Junior Seminars aim to intensify interactions between the MARVEL Junior scientists belonging to different research groups – this is held in hybrid mode, in order to maintain in-person contacts and allow off-campus attendees to follow the seminars remotely! We are pleased to propose the 63rd MARVEL Junior Seminar: Mauro Dossena (Integrated systems laboratory, ETHZ) and Stefan Riemelmoser (Chair of atomic scale simulation - CSEA, EPFL) will present their research. 

MARVEL Review and Retreat January 2025

The eleventh MARVEL Review and Retreat will take place on January 13-15, 2025. The event will gather all MARVEL members, group leaders as well as postdocs and students. Presentations will show to all the community where the projects stand and what are the next steps. 

MARVEL Distinguished Lecture — Alexandre Tkatchenko

The 39th NCCR MARVEL Distinguished Lecture will be given by Prof. Alexandre Tkatchenko, University of Luxembourg. He will be presenting a lecture entitled: "AI-Driven Fully Quantum Biomolecular Simulations".