Driven Correlated Materials and Dynamics of Exotic Ordering
Abstract
Many of the most intriguing macroscopic manifestations of quantum physics, such as insula- tor to metal transitions, magnetism and superconductivity, occur in so called strongly correlated materials. Here a strong coupling between electronic, vibrational and magnetic degrees of free- dom is present. Strong coupling between different order parameters, in particular when combined with geometric frustration, leads to a highly non-linear behavior of these materials. Under these circumstances, minute perturbations may cause major changes to a materials properties. While being of extraordinary relevance for the materials macroscopic behavior, it also limits coherence time of quasi-particles, and complicates the description of energy-flow between different degrees of freedom.
From a computational perspective, these are extremely challenging systems to tackle. The need to incorporate quantum-mechanical effects on equal footing as external electromagnetic fields, lattice vibrations and long-range spin-excitations demands both accuracy and computational ef- ficiency. Likewise, experimental interpretation of measurements on these systems are extremely challenging, and often computational support is needed in order to infer the origin of the measured signal as well as causality relations.
Within this project, we develop methods and software to describe these phenomena. We apply our developments to increase the understanding of strongly correlated materials, and aim for example to improve control of a materials conductivity by identifying the optimum conditions for switching between a materials phases.
To address the aforementioned challenges, we develop and apply computational tools based on the following methods
1) Time-dependent Density-Functional Theory (TDDFT) as implemented in the codes Elk and TDAP is used to describe ultrafast processes, such as pump-probe experiments.
2) Dynamic Mean-Field Theory (DMFT) as implemented in RSPt is used to describe correlated materials under thermal equilibrium.
3) Atomistic Spin-Dynamics as implemented in UppASD is used to describe e.g. dynamics in glassy systems, where system size and time-scales are beyond what can be described through first principles.
The project is funded by the following external grants and sources:
Coherent Control of Materials Properties, Swedish Research Council (VR),
PI: Oscar Grånäs
Ultrafast Resistive Switching for Bioinspired Devices, Carl Tryggers Stiftelse (CTS),
PI: Oscar Grånäs
Magneto-optical control of 2C nano-heterostructures for spintronics applications
PI: Oscar Grånäs
Theoretical Study of Co-Existent Exotic Magnetism and Unconventional Superconductivity
PI: Lars Nordström
Development projects are also funded through faculty funding of Lars Nordström and Anders Bergman
Through these projects, we adress the following work packages:
1) Simulation of ultrafast pump-probe processes in materials
2) Dynamics in unconventionally ordered spin-systems
3) Development of non-adiabatic exchange-correlation potentials for TDDFT
4) Optimal control of solid-state phases
