Periodic Reporting for period 2 - FASTCORR (Ultrafast dynamics of correlated electrons in solids)
Periodo di rendicontazione: 2021-12-01 al 2023-05-31
In FASTCORR, we develop the theory for driven quantum many-body systems that goes well beyond existing methods. This is accomplished by developing dynamical mean-field theory and its generalizations, e.g. the dual fermion and dual boson theory, to cover out-of-equilibrium phenomena.
A thorough understanding of how photons affect a material is crucial for the development of novel technologies where correlated electronic structures are important, e.g. superconductivity (electric distribution, Maglev trains, MRI scanners) and magnetism (electrical generators, transformers, data storage). The developments provided by us aim to create a solid theoretical foundation on which we can build practical tools that allow to interpret and predict ultrafast time-resolved phenomena of correlated electron systems. This involves (i) the development of fundamental mathematical and physical concepts, (ii) software development, and (iii) numerical simulations that are compared to experiments. Synergies between the three scientific approaches are crucial to achieving the goals of this project.
FASTCORR will result in novel high-performance software that we will distribute freely. These computational tools enable designed and targeted calculations for driven materials where the electronic structure is determined by strong correlation effects. The developed theory is used hand in hand with world-leading experimental works in the field of pump-probe measurements and spectroscopy, e.g. as investigated at X-ray free-electron laser laboratories.
A thorough understanding of how photons affect a material is crucial for the development of novel technologies where correlated electronic structures are important, e.g. superconductivity (electric distribution, Maglev trains, MRI scanners) and magnetism (electrical generators, transformers, data storage). The developments provided by us aim to create a solid theoretical foundation on which we can build practical tools that allow to interpret and predict ultrafast time-resolved phenomena of correlated electron systems. This involves (i) the development of fundamental mathematical and physical concepts, (ii) software development, and (iii) numerical simulations that are compared to experiments. Synergies between the three scientific approaches are crucial to achieving the goals of this project.
FASTCORR will result in novel high-performance software that we will distribute freely. These computational tools enable designed and targeted calculations for driven materials where the electronic structure is determined by strong correlation effects. The developed theory is used hand in hand with world-leading experimental works in the field of pump-probe measurements and spectroscopy, e.g. as investigated at X-ray free-electron laser laboratories.
Each node has focused on their area of expertise, as well as presenting their focus in a digestible manner for the other nodes, in order to facilitate the joint goal. Throughout the period, the full consortium has established a joint seminar series (weekly) and joint meetings (monthly) involving all participants from all three nodes.
Jointly the Nijmegen and Hamburg nodes have established a solid theoretical background on the theoretical description of magnetic properties of itinerant-electron systems out-of-equilibrium has been provided. The work solves the long-standing problem of full derivation of Landau-Lifshitz-type spin dynamics from completely microscopic treatment of correlated electron systems.
Additionally, these nodes have developed the theory for dual-fermions and dual bosons to describe degenerate plaquette physics in cuprate high-temperature superconductors. Our results give strong evidence that uncorrelated Cooper pairs exist above critical temperature, providing a new basis for understanding properties of superconducting cuprates in- and out-of-equilibrium. We have developed and present one of the first practical application of new many-body method for non-local interaction problem, to describe the coexistence of charge-density wave and ferromagnetic instabilities in monolayer InSe.
Jointly the Hamburg and Uppsala nodes have started the work on time-dependent impurity solvers for correlated electrons based on Monte-Carlo methods.
The Uppsala node has focused on theory for materials using realistic, many orbital calculations and has in these efforts interacted closely with experimental activities. For example, time-dependent density-functional theory was used to uncover a plausible origin in the scatter of experimental data on ultrafast demagnetization in alloys. In addition, in collaboration with experimental groups, time-resolved x-ray magnetic circular dichroism was measured and calculated to uncover spin-mixed states in ferromagnets. The Uppsala and Nijmegen groups, in collaboration with experimental partners, addressed the magnetisation dynamics of rare-earth systems and opened up a new research direction in the field. Establishing a new class of spin-glasses; the self-induced spin-glass systems (published in Science).
A fundamentally new approach to the generation of so-called pseudo-potentials for accelerated calculations of materials have been developed. This approach originates in a description of the solid, unlike the commonly used atomic approach. An efficient and reliable way to generate pseudo-potentials is crucial for many correlated oxides.
Jointly the Nijmegen and Hamburg nodes have established a solid theoretical background on the theoretical description of magnetic properties of itinerant-electron systems out-of-equilibrium has been provided. The work solves the long-standing problem of full derivation of Landau-Lifshitz-type spin dynamics from completely microscopic treatment of correlated electron systems.
Additionally, these nodes have developed the theory for dual-fermions and dual bosons to describe degenerate plaquette physics in cuprate high-temperature superconductors. Our results give strong evidence that uncorrelated Cooper pairs exist above critical temperature, providing a new basis for understanding properties of superconducting cuprates in- and out-of-equilibrium. We have developed and present one of the first practical application of new many-body method for non-local interaction problem, to describe the coexistence of charge-density wave and ferromagnetic instabilities in monolayer InSe.
Jointly the Hamburg and Uppsala nodes have started the work on time-dependent impurity solvers for correlated electrons based on Monte-Carlo methods.
The Uppsala node has focused on theory for materials using realistic, many orbital calculations and has in these efforts interacted closely with experimental activities. For example, time-dependent density-functional theory was used to uncover a plausible origin in the scatter of experimental data on ultrafast demagnetization in alloys. In addition, in collaboration with experimental groups, time-resolved x-ray magnetic circular dichroism was measured and calculated to uncover spin-mixed states in ferromagnets. The Uppsala and Nijmegen groups, in collaboration with experimental partners, addressed the magnetisation dynamics of rare-earth systems and opened up a new research direction in the field. Establishing a new class of spin-glasses; the self-induced spin-glass systems (published in Science).
A fundamentally new approach to the generation of so-called pseudo-potentials for accelerated calculations of materials have been developed. This approach originates in a description of the solid, unlike the commonly used atomic approach. An efficient and reliable way to generate pseudo-potentials is crucial for many correlated oxides.
During the reporting period, the state of the art has been advanced in the field of:
1) Out-of-equilibrium spin-dynamics in itinerant systems
2) Theory for high-temperature superconductivity
3) Description of fluctuations and coexistence of complex order in correlated materials
4) First-principles theory for time-resolved magnetization dynamics in magnetic alloys
5) Calculations of experimental observables in relation to x-ray spectroscopies
The ultimate goal of FASTCORR is to perform investigation for material with any type of multi-orbital correlations. In order to meet this ambitious goal, we will build on the aforementioned results to:
1) Merge our models for our-of-equilibrium spin-dynamics to first-principles methods via extraction of model parameters
2) Increase the efficiency of our developments within dual-fermion and dual-boson theory to address multi-orbital systems
3) Continued work on time-dependent impurity solvers will allow us to study complex order in correlated materials out-of-equilibrium
4) We will work on extending our first-principles techniques for out-of-equilibrium dynamics to include also strongly correlated electrons
5) Interface our techniques for x-ray spectroscopies with the newly developed out-of-equilibrium techniques for correlated electron systems to study transient experimental responses.
Further, we have ongoing work on data-mining for correlated materials, floquet Hamiltonians, efficient numerical algorithms.
Once our computational machinery is completed, we will put additional focus on the study of specific materials.
1) Out-of-equilibrium spin-dynamics in itinerant systems
2) Theory for high-temperature superconductivity
3) Description of fluctuations and coexistence of complex order in correlated materials
4) First-principles theory for time-resolved magnetization dynamics in magnetic alloys
5) Calculations of experimental observables in relation to x-ray spectroscopies
The ultimate goal of FASTCORR is to perform investigation for material with any type of multi-orbital correlations. In order to meet this ambitious goal, we will build on the aforementioned results to:
1) Merge our models for our-of-equilibrium spin-dynamics to first-principles methods via extraction of model parameters
2) Increase the efficiency of our developments within dual-fermion and dual-boson theory to address multi-orbital systems
3) Continued work on time-dependent impurity solvers will allow us to study complex order in correlated materials out-of-equilibrium
4) We will work on extending our first-principles techniques for out-of-equilibrium dynamics to include also strongly correlated electrons
5) Interface our techniques for x-ray spectroscopies with the newly developed out-of-equilibrium techniques for correlated electron systems to study transient experimental responses.
Further, we have ongoing work on data-mining for correlated materials, floquet Hamiltonians, efficient numerical algorithms.
Once our computational machinery is completed, we will put additional focus on the study of specific materials.