Computational Modeling of Out-of-Equilibrium Dynamics and of Superconductivity

Dnr:

NAISS 2024/1-25

Type:

NAISS Large Compute

Principal Investigator:

Peter Oppeneer

Affiliation:

Uppsala universitet

Start Date:

2024-07-01

End Date:

2025-07-01

Primary Classification:

10304: Condensed Matter Physics

Secondary Classification:

10302: Atom and Molecular Physics and Optics

Tertiary Classification:

10404: Inorganic Chemistry

Webpage:

The access to excellent computer resources has become a key ingredient in modern materials research. In the present proposal we are asking for computer time for mainly two research areas in which we are currently working. These research areas are computationally demanding; there is however an enormous scientific gain in terms of new knowledge, fundamental understanding, and materials' predictions that could not have been obtained otherwise.
In the first area we perform fully selfconsistent calculations of temperature-dependent superconductivity in real materials. To do this we have in the last years developed the Uppsala Superconductivity (UppSC) code, which is a full-bandwidth, multi-band, anisotropic Eliashberg code for selfconsistent calculations of unconventional superconductivity using full ab initio input from DFT calculations. This code is worldwide unique. It can e.g. treat phonon-mediated pairing and spin-fluctuations-mediated Cooper pairing, as well as conventional and unconventional multiband superconductivity. Until recent fully ab initio calculations of superconductivity have not been possible; we aim however at changing this situation. There are several computationally intensive steps needed to obtain temperature-dependent superconducting quantities (see proposal).
Another area on which we are currently working is the ab initio modeling of out-of-equilibrium dynamics to simulate ultrafast pump-probe experiments. Here we perform ab initio calculations of the strongly enhanced electron and lattice dynamics that occur in solid-state systems upon excitation with an ultrashort laser pulse. To this end we have developed a theory for describing the out-of-equilibrium ultrafast relaxation dynamics, which is completely ab initio based and takes all non-equilibrium processes (e.g., electron-phonon, electron-magnon, phonon-phonon interactions) into account. For the modeling we need to compute a number of quantities, such as phonon dispersions and lifetimes and wavevector and the mode dependent electron-phonon coupling.
A further area (not mentioned in the title) concerns state-of-the-art calculations for the emerging research field "orbitronics", which aims to employ in the future the orbital degree of freedom of electrons in solids instead of the electron's spin. The latter is already being used in spintronics. We aim to predict, on the basis of detailed electronic structure calculations, the current and also light induced orbital angular momentum in solids. These orbital moments and orbital currents are induced by the orbital Rashba-Edelstein effect and the orbital Hall effect, respectively. Recently, we have predicted giant induced orbital effects, that are much larger than their spin counterparts, opening thus a door to the future exploration of orbital angular momentum in future orbital-based electronics. Interestingly, theory is ahead of experiments in this field. Much ab-initio modeling will be required in the coming years to gain a thorough understanding of how orbital angular momentum is generated, transported through solids, and how it can be utilized in devices, e.g. to exert a torque on a magnetic layer.
Notably, the scientific gain achieved by performing these calculations is enormous which emphasizes the strength of computational materials modeling.