Electronic Structure Theory (Ali Alavi)

The Electronic Structure Theory department is interested in the development of ab initio methods for treating correlated electronic systems, using quantum chemistry and quantum Monte Carlo methods. These include full configuration interaction quantum Monte Carlo (FCIQMC), density matrix renormalization group methods, and many-body perturbation theories. Such methodologies are needed to accurately solve physical systems in which the ground (and excited state) electronic wavefunctions are strongly multiconfigurational (i.e. cannot be well-represented by a mean-field type wavefunction), and for which a high degree of basis-set flexibility is also necessary. Recent methodological progress has been the implementation of a spin-adapted FCIQMC algorithm based on the graphical unitary group formalism, which allows the efficient simulation of low-spin open-shell systems. Examples of such systems currently under investigation in our group are polynuclear transition metal clusters, such as [FeS] and [MnO] clusters of relevance to biological systems, and in the solid-state, cuprates and nickelates. We are also pursuing Transcorrelated methods, in which the electronic wavefunction is factorised using real-space Jastrow factors, which give rise to effective non-hermitian (similarity-transformed) hamiltonians. We have shown the such hamiltonians can be treated with the similarity-transformed FCIQMC technique. Transcorrelated wavefunctions can describe dynamical correlations and cusp conditions via explicit 2-body electron-electron and 3-body electron-electron-nuclear terms in the Jastrow factor, whilst static correlation is efficiently described by the multi-configurationality of the FCIQMC dynamics. It is our aim to extend the transcorrelated similarity-transformed FCIQMC method towards strongly correlated systems, including the 3d transition metal systems allused to above, allowing for an accurate and efficient description of both the strong dynamical and static correlations typically present in these systems. more
Solid State Spectroscopy (Bernhard Keimer)

Keimer's department studies the structure and dynamics of highly correlated electronic materials by spectroscopic and scattering techniques. Topics of particular current interest include the interplay between charge, orbital, and spin degrees of freedom in transition metal oxides, the mechanism of high-temperature superconductivity, and the control of electronic phase behavior in metal-oxide superlattices. High-quality single crystals and epitaxial thin-film structures are synthesized in close collaboration with other research groups at the Institute. Experimental techniques being used include elastic and inelastic x-ray and neutron scattering, neutron spin-echo spectroscopy, Raman scattering, and wide-band spectral ellipsometry. The department operates several beamlines at the research reactor FRM-II in Garching and at the PETRA-III synchrotron in Hamburg. The department also comprises a theory group, and it collaborates closely with the theory departments in the Institute on the analysis and interpretation of spectroscopic data. more
Nanoscale Science (Klaus Kern)

Research efforts in the Nanoscale Science department are centered on nanometer-scale science and technology with a focus on the bottom-up paradigm. The aim of the interdisciplinary research at the interface between physics, chemistry and biology is to gain control of materials at the atomic and molecular level, enabling the design of systems and devices with properties determined by quantum behavior on one hand and approaching functionalities of living matter on the other hand. more
Nanochemistry (Bettina Lotsch)

A central paradigm of nanochemistry is the rational synthesis of macroscopic materials based on nanoscale building blocks à la "Chimie douce". Imprinting materials with a nanostructure entails fundamental changes in their properties and opens up new avenues to the design of multifunctional materials with tailor-made properties. The Lotsch department employs modern techniques of nanochemistry and combines them with classical methods of solid-state synthesis to develop materials with complex property profiles, including two-dimensional systems and layered heterostructures, porous frameworks, photonic nanostructures, and solid electrolytes for applications in (photo)catalysis, sensing, and solid-state batteries. Our research vision is to translate fundamental research into sustainable material solutions to meet today’s global challenges, specifically in energy conversion and storage. more
Physical Chemistry of Solids (Joachim Maier)

Maier's department is concerned with physical chemistry of the solid state, more specifically with electrochemistry, chemical thermodynamics and transport properties. Emphasis is laid on ion conductors and mixed conductors. As local chemical excitations (point defects) are responsible for ion transport and simultaneously represent the decisive reactive centers, a major theme is the understanding of mass and charge transport and chemical reactivities in relation to defect chemistry. This includes experiments as well as theory and comprises investigations of elementary processes but also of overall system properties. In this context, interfaces and nanosystems are to the fore ("nanoionics"). Since electrochemistry addresses the coupling of chemical and electrical phenomena, the research is directed towards both basic solid state problems and the conversion of chemical energy and information (fuel cells, batteries, photoelectrochemical cells, chemical sensors). Conceptually speaking, we want to address the following questions: Can we – given the materials, the control parameters and the driving forces – understand or even predict concentrations, mobilities and reactivities of ionic charge carriers? How do these properties change at interfaces and in confined systems? What are the basic mechanisms of ion transport and ion transfer? How can we use this fundamental knowledge to develop at will materials for given (or novel) applications? more
Solid State Quantum Electronics (Jochen Mannhart)

Induced by quantum mechanical phenomena, heterostructures grown from complex materials offer a fascinating potential to create novel electron systems. Many have outstanding properties that are not otherwise found in nature. The design, growth, and exploration of such electron systems are at the focus of the department Solid State Quantum Electronics. Heterostructures are fabricated by building on recent advances made in the quantum engineering of novel materials, using advanced epitaxial growth techniques to deposit complex compounds with atomic-layer precision. Our experimental and theoretical efforts are interwoven with the other departments at the Institute. The goal of our research is to unravel the physics underlying artificial electron systems generated by interfaces and superlattice-type structures, to design and realize new ones, and to understand their potential for novel nanoscale devices that use the stunning effects of the quantum world to surpass the limits of today's electronics. more
Quantum Many-Body Theory (Walter Metzner)

Electronic properties of solids are analyzed and computed in Metzner's department with a main emphasis on systems where electronic correlations play a crucial role, such as cuprates and other transition metal oxides. Besides symmetry-breaking phase transitions leading to magnetism, orbital and charge order, or superconductivity, correlations can also cause electron localization and many other striking many-body effects not described by the independent electron approximation. Our research focuses in particular on high-temperature superconductors with their complex interplay of magnetic, superconducting and charge correlations, and also on manganites, titanates, and vanadates, whose electronic properties are determined by the interplay of orbital, spin and charge degrees of freedom. Besides bulk properties of one-, two- and three-dimensional systems, also surface states of topological phases, as well as problems with a mesoscopic length scale such as quantum dots, quantum wires, and quantum Hall systems are being studied. The correlation problem is attacked with various numerical and field-theoretical techniques: exact diagonalization, density matrix renormalization group, dynamical mean-field theory and functional renormalization group. Modern many-body methods are not only being applied, but also further developed within our group. more
Quantum Materials (Hidenori Takagi)

Entanglement of electrons (electron correlations) in solids, in combination with details of the crystal lattice structure, produce a surprisingly rich variety of electronic phases, that are liquid, liquid-crystal and crystalline states of the charge and spin degrees of freedom. These complex electronic phases and the subtle competition among them very often give rise to novel functionality. The department will be studying these interesting novel phases in transition metal oxides and related compounds where the narrow d-bands, which give rise to strong electron correlations, in combination with the rich chemistry of such materials provides excellent opportunities for new discoveries. The goal of this research will be to hunt for new materials exhibiting exotic electronic states of matter, showing phenomena such as superconductivity, quantum spin liquid and metal-insulator transition, and to explore them with advanced measurement techniques to unveil the physical mechanisms that could be drivers of potentially highly desirable functionality. more
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