Computational Physics

Electronic structures of metal hydrides and amorphous materials

Metal hydrides and amorphous materials are not only highly important in terms of industrial applications, but are also fascinating systems from a fundamental materials theory point of view. Exploring their rich electronic structure through computational modeling can offer new atomistic insights which could lead to far-reaching developments in experimental materials physics and engineering.

Developments in electronic structure theory

Physical properties of atoms, molecules and solids are determined by the collective behavior of electrons interacting with each other and with the nuclei. Unfortunately, an analytical solution of the electronic problem in a realistic system is often out of reach and one must resort to a numerical approach. In our group we contribute to developing various computational methods to solve the electronic problem in atoms, molecules and solids.

Functional Magnetic Materials

Magnetic materials are an essential part of our everyday life. Data storage, communication, and especially green energy production and electrical engines rely on magnetic materials based on high performance magnets which often contain critical components. Huge efforts are made to find suitable non-hazardous replacements. A new emerging field for magnetic materials is magnetic refrigeration. This can be an efficient way to cool environments, both homes as well as fridges and freezers in future.

Superconductivity from 1D electrons

The unique theoretical understanding available for correlated 1D electrons can be leveraged to design superconductors where electron pairing from repulsive interactions is understood, and the critical temperature for the onset of superconductivity could be increased based on accurate theory. This theory can not just be applied to propose novel superconducting devices and bulk materials, but also to understand pairing from repulsive electrons in existing unconventionally superconducting (USC) materials that are build from 1D structures (Bechgaard and Fabre salts, Sr-ladder compounds, K₂Cr₃As₃).

Oxide Heterostructures

The interfaces of oxide heterostructures provide a strong interplay between spin, orbital, charge and lattice degrees of freedom. Their careful tuning may lead to artificially designed materials with novel properties, opening the possibility to have new design concepts of future nanodevices. Specifically, the interfaces of transition metal oxide heterostructures may give rise to two-dimensional electron gas, charge transfer and charge migration along with complex magnetic phenomena, which can be useful for technological applications.

Theoretical Spectroscopy

Modern photon and electron beam sources make it possible to probe excitation spectra in many systems, ranging from atoms and molecules to bulk materials and complex interfaces. The interpretation of the experimental data is, however, problematic without an adequate theoretical support. To address this, we develop theories for predicting and analyzing spectra measured in different experiments, as e.g. (angle-resolved) photoemission spectroscopy, magneto-optical spectroscopy, X-ray emission and X-ray absorption, electron energy loss spectra, as well as resonant inelastic X-ray scattering.

On-surface Magnetochemistry and Spintronics

Spin-bearing metalorganic molecules provide a unique platform for exploiting spin properties, leading to molecular spintronics and on-surface magnetochemistry, an emergent area in which reversible switching of the molecule’s spin is utilized.

To prepare the way for spin-switchable single-molecule electronic devices, we perform fundamental investigations of the complex interplay of chemical and magnetic interactions in metalorganic systems, using density-functional-theory-based methodologies.

Electronic structure of metal hydrides and amorphous materials II

Despite the simplest possible electronic structure of hydrogen, tremendous complexity can arise when it participates in the formation of solids. We have predicted crystal structures of metal hydrides under pressure and utilized the stochastic quenching method to understand the role that hydrogen can play in affecting electronic properties of certain amorphous materials.

Magnetism

We investigate the magnetic properties of transition and rare-earth metals in bulk, multilayer, surface and cluster geometries. We also study the magnetism of novel superconductors, complex oxides and dilute magnetic semiconductors.

Molecular electronics

Molecular electronics is a rapidly developing research field at the interface of physics, chemistry, and engineering, in which electron transport through molecules is investigated. The project involves design and ab initio simulations of molecular structures, metal and semiconductor surfaces and molecular adsorption applied to molecular electronics, biological and nano-sensors and synthesis of novel materials. Our research is performed within the environment of the Uppsala University UniMolecular Electronics Center (U³MEC) which focuses on molecular electronics based on single or small assemblies of molecules.

Nanobiotechnology

Nanobiotechnology is a hot new research field in which nano-sized artificial structures are combined with natural biological systems for a broad range of purposes, among them bio-sensing and drug delivery. We are active in both these research areas.

On-surface magnetochemistry and spintronics II

Organic molecules are multifunctional materials that are promising for many technological applications. They are cheap materials that can be mass-produced and their functionalities can moreover easily be tailor-made by chemical synthesis. Therefore they are ideally suited for achieving the goal of sustainable development. Spin-bearing metalorganic molecules provide a unique platform for exploiting in addition spin properties, leading to molecular spintronics and on-surface magnetochemistry, an emergent area in which adsorption/desorption of an extraneous molecule is employed to realize reversible switching of the molecule’s spin.

Oxide heterostructures II

Geometry and magnetic structure of LSMO/YMnO3 interface. We study the interplay of spin, orbital and lattice degrees of freedom at the interfaces of functional oxide heterostructures. Complex magnetic structures, ferroelectric polarization and effects of electron correlation are investigated at the interfaces by ab initio calculations.

Theoretical spectroscopy II

In order to meet the challenges of modern synchrotron radiation facilities, we develop theories for analyzing the experimental results that are produced in these facilities. This involves calculations of x-ray and photoelectron spectra of molecules, interfaces and bulk materials.