ELECTRONIC PROPERTIES AT THE NANOSCALE
The research line on “Electronic Properties at the Nanoscale” focuses on the electronic properties of solids, surfaces, nanostructures, and low-dimensional systems. Research within the line tackles the electronic properties both of ground and excited states of these systems. In particular, the electronic response of materials under different perturbations, i.e., different experimental probes (electromagnetic radiation, electrons, ions, etc.) is investigated. The way in which size, border, and dimensionality effects can change the properties of nanosized materials is under scrutiny.
Five research groups are included in this purely theoretical research line. The activity of all groups together covers the theoretical study of a wide range of materials, including both the microscopic and the mesoscopic scales, based on state-of-the-art methodologies. The list of research groups follows:
THE RESEARCH GROUPS
ELECTRONIC EXCITATIONS IN SURFACES AND NANOSTRUCTURES
The “Electronic Excitations in Surfaces and Nanostructures” group, mostly devoted to the theoretical study of electron dynamics in solids, surfaces, nanoscale systems and materials of technological interest. Furthermore, electronic and magnetic properties of materials are obtained using first principles methodologies. Electron dynamics in different systems is investigated, with particular emphasis on ultrafast processes and size effects. Advanced materials, such as topological insulators and cement-related systems are current targets of the group´s research.
MATERIALS COMPUTATION AND THEORY
“Materials Computation and Theory” group focuses into first-principles electronic structure calculations to analyze and understand materials properties, in particular optical, electronic and magnetic properties, as well as superconductivity. A theoretical analysis of the experimentally observed, and still not completely understood, anomalous physical properties associated to the increasing pressure induced electronic correlation is also addressed.
“Mesoscopic Physics” group is devoted to the theoretical study of the properties of mesoscopic systems, as well as to the study of quantum transport in metals, ferromagnets, semiconductors, superconductors, cold-atoms systems, organic materials and insulators. The main goal of the group is the development of theoretical frameworks to describe several phenomena related to quantum transport in mesoscopic systems, such as the coexistence of ferromagnetism and superconductivity, heat transport in nanostructures, quantum coherence in hybrid systems, and strongly correlated systems.
“Nano-bio Spectroscopy” group focuses on the theory and modelling of electronic and structural properties in condensed matter and on developing novel theoretical tools and computational codes to investigate the electronic response of solids and nanostructures to external electromagnetic fields. Present research activities include new developments within many-body theory and TDDFT. The theoretical description of optical spectroscopy, time-resolved spectroscopies, STM/STS and XAFS is also addressed. Methodological developments include novel techniques to calculate total energies and assessment and development of exchange-correlation functionals for TDDFT calculations and improvements on transport theory within the real-time TDDFT formalism.
QUANTUM PHENOMA ON SURFACES
The scanning tunneling microscope (STM) probes the electronic properties of condensed-matter systems by smoothly injecting or removing electrons. Assuming that the machine does not perturb the system, the electronic structure seen by propagating an electron or a hole is exactly what the spectral function does. In other words, the STM reads the spectral function of real systems. The line of research in this group is to develop computational schemes to unveil all the richness of realistic spectral functions. The group is thus interested in electronic, vibrational and magnetic excitations. The Kondo effect is an unavoidable phenomenon of systems that present time-reversal symmetry and electron scattering. Particle pairing like in superconductors is also very exciting. Trying to understand the many different systems and yield quantitative explanations for the several experimental data obtained in STM laboratories around the globe is also this group’s goal.
Several computing clusters at the CFM and other institutions (such as DIPC) under collaborative research. Several scientific codes for ab initio calculations (DFT based on plane waves and local orbitals, quantum chemistry), as well as other computational and graphic packages.
Development of scientific software for ab initio calculations, including time-dependent propagation, electromagnetic and optical response, as well as for other methodologies. Development of packages freely distributed to the scientific community (e.g., OCTOPUS for time-dependent density functional theory calculations).