Die Max Planck Lecture wurde 2003 von den beiden Stuttgarter Max-Planck-Instituten ins Leben gerufen und wird von bedeutenden Wissenschaftlern und Experten ihres Fachs auf dem Max-Planck-Campus in Stuttgart-Büsnau gehalten. Die Institute für Festkörperforschung (FKF) und Intelligente Systeme (IS) (ehemals Metallforschung) tragen gemeinsam die Max Planck Lecture und laden beide je einmal jährlich einen Sprecher ihrer Wahl zum Vortrag ein. Dieser richtet sich an Forscherkollegen, Projektpartner aus der Industrie, wissenschaftspolitsche Entscheidungsträger und Personen mit naturwissenschaftlichem Interesse.
Sprecher der Max Planck Lecture
29.09.2023 / FKF
Professor Satoru Nakatsuji
The University of Tokyo, Japan
"Designing Topological Magnetic Materials for Innovative Quantum Electronics"
The concept of topology in electronic structure has reshaped our understanding of materials properties, driving the discovery of various classes of systems such as topological insulators and nodal-point and nodal-line semimetals. In this talk, we show that by introducing such a notion of topology or quantum Berry phase in magnets, one may find novel properties useful for designing innovative quantum electronics. A prominent example is the antiferromagnetic Weyl semimetal Mn3Sn, in which we discovered a large anomalous Hall effect for the first time in antiferromagnets. This further has enabled us to develop novel spintronic functionalities that have previously been thought absent for anti-ferromagnets, such as bidirectional electrical switching and quantum tunneling magnetotransport, paving a path for ultrafast operation of non-volatile memory. The second example is a ferromagnetic nodal line semimetal, producing the largest ever anomalous Nerst effect (ANE) at room temperature. In particular, a quantum Lifshitz phase transition of the Weyl cone may lead to the divergence in the transverse thermoelectric conductivity. Compared to the conventional Seebeck effect, the enhanced ANE is useful for distinct thermoelectric applications through a simplified fabrication process, extensive area coverage, and enhanced flexibility. Finally, I will discuss the perspective of designing topological magnetic materials and their applications for quantum electronics.
07.07.2022 / FKF
Professor Pablo Jarillo-Herrero
Massachusetts Institute of Technology, Department of Physics, Cambridge, MA, USA
"The Magic of Moiré Quantum Matter"
The understanding of strongly-correlated quantum matter has challenged physicists for decades. The discovery three years ago of correlated phases and superconductivity in magic angle twisted bilayer graphene led to the emergence of a new materials platform to investigate strongly correlated physics, namely moiré quantum matter. These systems exhibit a plethora of quantum phases, such as correlated insulators, superconductivity, magnetism, Chern insulators, and more. In this talk I will review some of the recent advances in the field, focusing on the newest generation of moiré quantum systems, where correlated physics, superconductivity, and other fascinating phases can be studied with unprecedented tunability. I will end the talk with an outlook of some exciting directions in this emerging field.
22.07.2022 / IS
Professor Zhenan Bao
K.K. Lee Professor and Department Chair in the Department of Chemical Engineering, Stanford, CA , USA
"Skin-Inspired Organic Electronics"
10.03.2022 / FKF
Professor Bilge Yildiz
Massachusetts Institute of Technology, Cambridge, USA
"Understanding and tuning the surface chemistry of perovskite oxides to activate oxygen exchange and water splitting reactions"
The deployment of decarbonization technologies, including solid oxide fuel and electrolysis cells, is limited by slow rates of conversion reactions at surfaces, and instability of materials under operating conditions. A major scientific challenge has been the lack of knowledge of the chemistry and electronic structure on material surfaces in the harsh operational conditions. Bulk transport properties of state-of-the-art perovskite type oxides in these applications are well-studied. In contrast, how the surfaces of these materials are affected by the electrochemical environment at elevated temperatures, and how these surfaces in turn affect the conversion reactions, including oxygen exchange and water splitting, have not been fully explored. Yet it is the surface that governs the reaction kinetics. In this talk, I will first discuss our research in revealing the chemical and electronic nature of surfaces in relation to oxygen exchange reactions on perovskite oxides, using in situ surface-sensitive techniques and with first-principles-based calculations. This new knowledge has guided us to design surface chemistries that eliminate a key degradation mode at the surface, and improve both activity to oxygen exchange reactions and stability. Second, I will discuss our research in understanding and controlling the formation of metal nanoparticles at perovskite oxide surfaces, to catalyze water splitting reactions. This process, called exsolution, has attracted great interest as a means to form stable metal catalyst particles on oxide supports. However, the physical factors that control the size and density of such exsolved particles are far from quantified at preset. Our research using lattice strain and ion irradiation, has shown that point defects have a key role in affecting both the thermodynamics and the kinetics of the exsolution process. Furthermore, we have revealed how the near surface region and the interior of the perovskite oxide, can undergo drastic chemical and structural changes during the metal exsolution process, with significant implications to surface reactivity as well as bulk electronic and magnetic properties. While this body of work has been pursued in the context of solid oxide fuel and electrolysis cells, the findings broadly impact also other fields that use perovskite oxides, such as in photo-electrochemical and thermochemical splitting of water, CO2 reduction, and memristive information processing.
23.06.2020 / IS
Professor Yoshua Bengio
Université de Montréal
"Machine Learning for Covid-19 Risk Awareness from Contact Tracing"
The Covid-19 pandemic has spread rapidly worldwide, overwhelming manual contact tracing in many countries, resulting in widespread lockdowns for emergency containment. Large-scale digital contact tracing (DCT) has emerged as a potential solution to resume economic and social activity without triggering a second outbreak. Various DCT methods have been proposed, each making trade-offs between privacy, mobility restriction, and public health. Many approaches model infection and encounters as binary events. With such approaches, called binary contact tracing, once a case is confirmed by a positive lab test result, it is propagated to people who were contacts of the infected person, typically recommending that these individuals should self-quarantine. This approach ignores the inherent uncertainty in contacts and the infection process, which could be used to tailor messaging to high-risk individuals, and prompt proactive testing or earlier self-quarantine. It also does not make use of observations such as symptoms or pre-existing medical conditions, which could be used to make more accurate risk predictions. Methods which may use such information have been proposed, but these typically require access to the graph of social interactions and/or centralization of sensitive personal data, which is incompatible with reasonable privacy and security constraints. We use an agent-based epidemiological simulation to develop and test ML methods that can be deployed to a smartphone to locally predict an individual's risk of infection from their contact history and other information, while respecting strong privacy and security constraints. We use this risk score to provide personalized recommendations to the user via an app, an approach we call probabilistic risk awareness (PRA). We show that PRA can significantly reduce spread of the disease compared to other methods, for equivalent average mobility and realistic assumptions about app adoption, and thereby save lives.
22.10.2018 / IS
Professor Roland Siegwart
"Autonomous Robots that Walk and Fly"
While robots are already doing a wonderful job as factory workhorses, they are now gradually appearing in our daily environments and offering their services as autonomous cars, delivery drones, helpers in search and rescue and much more. This talk will present some recent highlights in the field of autonomous mobile robotics research and touch on some of the great challenges and opportunities. Legged robots are able to overcome the limitations of wheeled or tracked ground vehicles. ETH’s electrically powered legged quadruped robots are designed for high agility, efficiency and robustness in rough terrain. This is realized through an optimal exploitation of the natural dynamics and serial elastic actuation. For fast inspection of complex environments, flying robots are probably the most efficient and versatile devices. However, the limited payload and computing power of drones renders autonomous navigation quite challenging. Thanks to our custom designed visual-inertial sensor, real-time on-board localization, mapping and planning has become feasible and enables our multi-copters and solar-powered fixed wing drones for advanced rescue and inspection tasks or support in precision farming, even in GPS-denied environments.
12.10.2018 / FKF
Prof. Dr. Hideo Hosono
Tokyo Institute of Technology, Japan
"Transparent Amorphous Oxide Semiconductors: from materials design to implementation to state of the art displays"
Thin film transistor (TFTs) is a fundamental building block in electronic circuits. Since the specification for TFTs to drive the pixel of flat panel displays rather differs from that for CPUs and memories because of their large dimension. Amorphous semiconductors have distinct advantages in the formation of large-sized homogeneous thin films at low temperatures but their Fermi level control by impurity doping or field effect is generally impossible due to high density carrier traps arising from structural randomness of amorphous structure. Amorphous hydrogenated silicon (a-Si:H) is an exceptional semiconductor in which Fermi level is controllable but the mobility remains 0-5-1 cm2/Vs, which is lower by 2 orders of magnitude than that of polycrystalline Si. Their performance was, however, enough to drive liquid panel displays which are driven by voltage. This is the main reason why a-Si:H has been exclusively applied as the channel material of TFTs for driving LCDs, and the display market has now grown to >$100 billion.
Next generation displays such as large-sized high definition LCDs and organic light emitting diodes (OLEDs) needs higher mobility TFTs. In 1995, I proposed a material design concept for transparent amorphous oxide semiconductors (TAOS) with high electron mobility on the basis of a simple consideration of chemical bonding along with several concrete materials. After the validity of this concept was verified by a combined research of experiment and computation, we reported transparent TFTs using In-Ga-Zn-O (IGZO) which is a member of TAOS materials in 2003 and 2004.
The mobility of a-IGZO TFTs fabricated by conventional sputtering method is higher by an order of magnitude than that of a-Si:H. Demonstrations of IGZO TFT-based displays began to emerge in 2007, when Samsung Electronics first reported a-IGZO TFT-based high-definition LCDs. Demonstrations of IGZO TFT-based backplane LCDs in smart phones and tablet computers then appeared around 2012. Arguably the most striking application emerged in 2015, when LG Display demonstrated large-sized OLED televisions. You can see now the beautiful images of 55' and 65' OLEDs TVs in electrical stores and so on. IGZO-TFTs are going to be implemented to large-sized and 8K LCD-TVs. In this lecture, I will talk a research story on TAOS from fundamental idea for materials to technical progress for implementation to displays .
18.09.2017 / IS
Prof. Amnon Shashua
Co-founder, CTO, and Chairman of Mobileye Vision Techonologies Ltd.;
Sachs Professor of Computer Science at Hebrew University
"The Three Pillars of Fully Autonomous Driving"
The field of transportation is undergoing a seismic change with the coming introduction of autonomous driving. The technologies required to enable computer driven cars involves the latest cutting edge artificial intelligence algorithms along three major thrusts: Sensing, Planning and Mapping. Prof. Amnon Shashua, Co-founder and Chairman of Mobileye, will describe the challenges and the kind of machine learning algorithms involved, but will do that through the perspective of Mobileye’s activity in this domain.
18.05.2017 / FKF
Robert J. Birgeneau
Professor and Chancellor Emeritus, University of California at Berkeley
"Superconductors Old and New"
Solid State Physics is a field which continuously renews itself through the discovery of new materials and new phenomena. This has been particularly true for the subfield of superconductivity. We will review the progress in this field from Kammelingh Onnes's discovery of superconductivity in mercury in 1911 to the Bednorz-Mueller ground breaking discovery of high temperature superconductivity in the lamellar copper oxides in 1986 to recent work on the Fe arsenides and selenides. Research on superconductivity has produced theoretical insights which have implications not only for superconductivity itself but for systems as varied as liquid crystal gels to the fundamental constituents of the universe.
06.06.2016 / IS
Professor Naomi Ehrich Leonard
Princeton University, USA
"On the Nonlinear Dynamics of Collective Decision-Making in Nature and Design"
The successful deployment of complex, multi-agent systems requires well-designed, agent-level control strategies that accommodate sensing, communication, and computational limitations on individual agents. Indeed, many applications demand system-level dynamics to be robust to disturbance and adaptive in the face of changes in the environment. Remarkably, animal groups, from bird flocks to fish schools, exhibit just such robust and adaptive behaviors, even as individual animals have their own limitations. To better understand and leverage the parallels between networks in nature and design, a principled examination of collective dynamics is warranted. I will describe an analytical framework based on nonlinear dynamical systems theory for the realization of collective decision-making that allows for the rigorous study of the mechanisms of observed collective animal behavior together with the design of distributed strategies for collective dynamics with provable performance.
20.05.2015 / FKF
Professor Wolfgang Ketterle
Massachusetts Institute of Technology, Cambridge
"Ultracold atoms as quantum simulators for new materials – synthetic magnetic fields and topological phases"
When atoms are cooled to nanokelvin temperatures, they can easily be confined and manipulated with laser beams. Their interactions can be tuned with the help of magnetic fields, making them strongly or weakly interacting, repulsive or attractive. Crystalline materials are simulated by placing the atoms into an optical lattice, a periodic interference pattern of laser beams. Recently, synthetic magnetic fields have been realized.With the help of laser beams, neutral atoms move around in the same way as charged particles subject to the magnetic Lorentz force. These developments should allow the realization of quantum Hall systems and topological insulators with ultracold atoms.
09.03.2015 / IS
Vijay Kumar, Ph.D.
University of Pennsylvania, UPS Foundation Professor School of Engineering and Applied Science
"Aerial Robot Swarms"
Autonomous micro aerial robots can operate in three-dimensional, indoor and outdoor environments, and have applications to search and rescue, fi rst response and precision farming. I will describe the challenges in developing small, agile robots and the algorithmic challenges in the areas of (a) control and planning, (b) state estimation and mapping, and (c) coordinating large teams of robots.
22.05.2014 / IS
Professor A. L. Greer
University of Cambridge, Department of Materials Science & Metallurgy
"The Glassy State properties and applications exploiting non-crystallinity: golf, frozen frogs, memory"
Glasses, lacking the order of crystals, are in many ways still regarded as poorly understood. Yet glasses, lacking the complications of different crystallographic symmetries, also show some remarkable correlations of diverse properties. Modern studies show the wide range of possibilities for exploiting the glassy state – and that state is certainly not confined to conventional silicate systems (familiar in windows, spectacles and drinking vessels). This talk will focus on more exotic glassy systems. A few of these will be presented, touching on such questions as: how to do better at golf, how not to freeze (or indeed desiccate) to death, and how to improve your (computer’s) memory. The scientific focus is on the comparison of, and transitions between, crystalline and glassy states, treating questions of crystal nucleation and growth. The aim is to show that these questions are not only of fundamental scientific interest; they have important practical applications in structures, medicine and information technology.
10.10.2013 / IS
Prof. Dr. Paul Chaikin
New York University, Department of Physics
"Some Small Steps toward Artificial Life"
No one has successfully defined life but the properties we often associate with living things are motility, metabolism and self-replication. According to the Nobel Laureate Richard Feynman: "What I can't create, I don't understand". We thought we'd give it a shot – understanding life – and in the process we've made two different systems, one that exhibits both autonomous motility and metabolism and another which is the first artificial system which can replicate arbitrarily designed motifs.
The first system, artificial swimmers, provides insight into many natural phenomena such as a flocking of birds and schooling of fish.
The second system uses diurnal cycles of temperature and light and at present is doubling each cycle, growing exponentially. It provides a new way of producing many, many copies of nanoscale devices and may give insights into the origin of conventional life on earth.
08.05.2013 / FKF
Dr. Ivan Božović
Brookhaven National Laboratory, USA
Interface Science. The last decade has witnessed explosive growth of research on various oxide heterostructures, and discoveries of exciting new interface phenomena. We may be witnessing the emergence of a new scientific discipline – Interface Science, delineated by a distinct new set of problems, techniques, phenomena, and theoretical concepts.
Electronic and/or atomic reconstruction. In heterostructures there is always some mismatch between the two constituents – crystallographic (different lattice constants), electrostatic (violation of local charge
neutrality) or dynamic (difference in chemical potentials). Consequences are numerous and profound. The atomic structure can be strained and modified; electronic and/or atomic reconstruction may occur, including formation of oxygen and/or cation vacancies as well as large atomic displacements.
Metastability. Most heterostructures are not thermodynamically stable; the synthesis is at least in part kinetically controlled and the atoms are frozen in one out of many nearly-degenerate metastable states. The
actual atomic structure at the interface is thus basically impossible to predict. To determine it experimentally, new tools and techniques for study of buried interfaces are required, and being developed fast.
2D quantum confinement. Digital synthesis of complex oxides – one-unit-cell or even one-atomic-layer at a time – yields ultrathin layers with atomically sharp interfaces. Electrons can be extremely confined in one direction, while propagating with high mobility in-plane. Ultrathin metals, superconductors, ferromagnets or ferroelectrics host new phenomena, such as massive critical fluctuations, thermal or quantum.
Proximity effects. Interesting new physics occurs also when the two materials exhibit different broken symmetries and order parameters. Competing instabilities, if finely balanced, can result in extreme susceptibility and colossal responses to small perturbations. These may find applications in sensing, ultrafast non-volatile switching, etc., and is hoped to eventually beget new Oxide Electronics.
In this lecture, a number of simple examples will be given, largely drawn from my own practice with atomic-layer-by-layer molecular beam epitaxy (ALL-MBE) of high-Tc cuprate superconductors, but intended to illustrate the more general concepts listed above.
05.12.2012 / FKF
Prof. Dr. Clare P. Grey
University of Cambridge, Department of Chemistry & Stony Brook University, Department of Chemistry
"Following Function in Real Time: New NMR, MRI and Diffraction Methods for Studying Structure and Dynamics in Batteries and Supercapacitors"
A full understanding of the operation of a device requires that we utilize methods that allow devices or materials to be probed while they are operating (i.e., in-situ). This allows, for example, the transformations of the various cell components to be followed under realistic conditions without having to disassemble and take apart the cell. To this end, the application of new in and ex-situ Nuclear Magnetic Resonance (NMR) and magnetic resonance imaging (MRI) approaches to correlate structure and dynamics with function in lithium-ion and lithium air batteries, and supercapacitors will be described. The in-situ approach allows processes to be captured, which are very difficult to detect directly by ex-situ methods. For example, we can detect side reactions involving the electrolyte and the electrode materials, sorption processes at the electrolyte-electrode interface, and processes that occur during extremely fast charging and discharging. Ex-situ NMR investigations allow more detailed structural studies to be performed to correlate local and long-range structure with performance. In this talk, I will describe the use of NMR spectroscopy combined with X-ray scattering methods to probe local structure changes in lithium ion batteries, focusing on our work with the anodes material Si and LiVO2, on lithium air cathodes, and to investigate Li dendrite formation in lithium metal batteries. Finally, the application of NMR to examine double layer formation in electrolyticdouble layer capacitors (supercapacitors) will be described.
26.09.2012 / IS
Prof. Dr. Robert Wood
Harvard University, School of Engineering and Applied Sciences
"Progress on biologically-inspired microrobots"
As the characteristic size of a flying robot decreases, the challenges for successful flight revert to basic questions of fabrication, actuation, fluid mechanics, stabilization, and power – whereas such questions have in general been answered for larger aircraft. When developing a flying robot on the scale of a common housefly, all hardware must be developed from scratch as there is nothing "off-the-shelf" which can be used for mechanisms, sensors, or computation that would satisfy the extreme mass and power limitations.
This technology void also applies to techniques available for fabrication and assembly of the aeromechanical components: the scale and complexity of the mechanical features requires new ways to design and prototype at scales between macro and MEMS, but with rich topologies and material choices one would expect in designing human-scale vehicles. With these challenges in mind, this talk will present progress in the essential technologies for insect-scale robots.
14.10.2011 / IS
Prof. Dr. Martin Nowak
Harvard University, USA
"Evolution of cooperation"
Cooperation implies that one individual pays a cost for another to receive a benefit. Cost and benefit are measured in terms of reproductive success. Cooperation is useful for construction in evolution: genomes, cells, multi-cellular organisms, animal and human societies are consequences of cooperation. Cooperation can be at variance with natural selection. Why should you help competitors? I present five mechanisms for the evolution of cooperation: kin selection, direct reciprocity, indirect reciprocity, spatial selection and group selection. Direct reciprocity means there are repeated interactions between the same two individuals and my behavior towards you depends on what you have done to me. Indirect reciprocity means there are repeated interactions within a group and my behavior towards you also depends on what you have done to others. I argue that indirect reciprocity is the key mechanism for understanding pro-social behavior among humans and has provided the right selection pressure for the evolution of social intelligence and human language.
03.03.2011 / FKF
Prof. Dr. Michael Grätzel
Ecole Polytechnique Fédérale de Lausanne, Laboratory of Photonics and Interfaces
"The advent of mesoscopic solar cells"
The field of photovoltaic cells has been dominated so far by solid state p-n junction devices made e.g. of crystalline or amorphous silicon, profiting from the experience and material availability of the semiconductor industry. However, there is an increasing awareness of the possible advantages of devices referred to as "bulk" junctions due to their interconnected three-dimensional structure. Their embodiment departs completely from the conventional flat p-n junction solid-state cells, replacing them by interpenetrating networks.
This lecture focuses on dye sensitized mesoscopic solar cells (DSCs), which have been developed in our laboratory. Imitating the light reaction of natural photo-synthesis, this cell is the only photovoltaic device that accomplishes the separation of the optical absorption from the charge separation and carrier transport processes. It does so by associating a molecular dye with a film constituted of tiny particles of the white pigment titanium dioxide. The DSC has made phenomenal progress, present conversion efficiencies being over 12 percent for single junction and 17 percent for tandem cells, rendering the DSC a credible alternative to conventional p-n junction devices. Commercial large-scale production of flexible DSC modules has started in 2009. These solar cells have become viable contenders for large-scale future solar energy conversion systems on the bases of cost, efficiency, stability and availability as well as environmental compatibility.
27.05.2010 / MF
Prof. Dr. Subra Suresh
Massachussetts Institute of Technology, USA
"Materials Science Aproaches for Life Sciences and Human Health"
This lecture will provide recent research results at the intersections of engineering, materials science, nanotechnology, genetics, life sciences, medicine and public health.
Particular attention will be devoted to the role research at the intersections of these different fields plays in advancing the boundaries of human disease diagnostics, therapeutics and drug efficacy assays, through experiments, computations, and clinical studies.
Specific examples will include research results for infectious diseases, human cancer, blood disorders and traumatic brain injury.
23.11.2009 / FKF
Prof. Dr. Harold Y. Hwang
University of Tokyo, Department of Advanced Materials & Department of Applied Physics
"Atomic Engineering Oxide Heterointerfaces"
Complex oxides are fascinating systems which host a vast array of unique phenomena, such as high-temperature (and unconventional) superconductivity, "colossal" magnetoresistance, all forms of magnetism and ferroelectricity, as well as (quantum) phase transitions and couplings between these states. In recent years, there has been a mini-revolution in our ability to grow thin film heterostructures of these materials with atomic precision. With this level of control, a number of new electronic phases have been discovered at their interfaces. Between two insulators, for example, metallic, superconducting, and mag-netic states can be induced. In analogy to the rich science and technology that emerged from the development of semicon-ductor heterostructures, we are using these techniques to create novel low-dimensional states inaccessible in bulk oxides.
08.06.2009 / MF
Prof. Dr. Yves Bréchet
SIMAP, Grenoble Institute of Technology, France
"Architectured Materials and Multifunctional Designs: Foams, Wools and Interlocked Materials"
Developing new materials via a better understanding of the mechanisms underlying macroscopic properties has been the Graal of materials science. The most prominent effort in Materials Science has been toward a better control of the microstructure, toward smaller and smaller scales, and in recent years, toward nanomaterials. In Structural Mechanics, shape optimisation has played a similar role in providing an optimised used of matter to develop very large structures. The intermediate scale, that we will call "Millimaterials", offer a number of opportunities for new materials development. Materials with a millimetric architecture such as foams, felts, lattices can be used for sound absorbers.
Interlocked Materialsmay provide damage tolerance to intrinsically brittle materials. Graded Materials can provide good compromises for high strength materials. But optimaldisign of this new class of materials, able to fill important "gaps"in Materials properties space, requires an intensive use of medelling. Physically based modelling as a guide to architectured materials optimisation strategy will be illustrated on example like felts, hollow spheres foams, interlocked materials.
15.10.2008 / FKF
Prof. Dr. Moty Heiblum
Braun Center for Submicron Research, Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot, Israel
"Electron Interference in two Dimensions: Phase Measurements, Controlled Dephasing and Phase Recovery"
Electron interference in the solid enables to determine the electron coherence time, the phase electron gains during transport, the statistics of quasi-particles in strongly interacting systems, and the processes of dephasing. A few examples of electron interferometers constructed in two-dimensional electron gas will be provided and the following experiments will be described:
- the evolution of phase electrons accumulate as they traverse a coherent quantum dot,
- a simulation of an environment interacting with an interferometer by constructing a 'which path' detector, and
- the recovery of the phase in an already dephased system via experimentally 'looking' at only a part of the data ('post selection' measurements).
22.07.2008 / MF
Prof. Dr. A. Paul Alivisatos
Lawrence Berkeley National Laboratory, USA
"Nanocrystals as Model Systems for Understanding Structural and Chemical Transformations in the Solid State"
The advent of means to prepare well-controlled nanoscale building blocks has opened up many new opportunities to understand difficult problems which lie at the core of materials science. As an example, nanometer-size inorganic nanocrystals can be transformed from one state to another with remarkably simplified kinetics compared to extended or bulk solids.
This talk will present results on the nanoscale kirkendall effect, on cation exchange in nanocrystals, and shock-wave studies of structural transformations in nanocrystals, In each one, fundamental impact of the transformations, whichare obscured in bulk experiments, can be more reliably observed and understood in the case of nanocrystals.
11.07.2007 / FKF
Prof. Dr. Peidong Yang
University of California, Department of Chemistry, Berkeley
"Nanowire Building Blocks for Photonics & Energy Conversion"
Nanowires are of both fundamental and technological interest. They represent the critical com-ponents in the potential nanoscale electronic and photonic device applications. In our lab, the vapor-liquid-solid crystal growth mechanism has been utilized for the general synthesis of nano-wires of different compositions, sizes, and orientation. Precise size control of the nanowires can be readily achieved using metal nanocrystals as the catalysts. Epitaxial growth plays a signifi-cant role in making such nanowire heterostructures and their arrays. To this end, we have successfully synthesized superlattice nanowires and core-sheath nanostructures. Achieving high level of synthetic control over nanowire growth allows us to explore some of their very unique physical properties. For example, semiconductor nanowires can function as self-contained nanoscale lasers, sub-wavelength optical waveguides, photodetector and efficient nonlinear optical mixer. It was also discovered that the thermoconductivity of the silicon nano-wires can be significantly reduced when the nanowire size in the 20 nm region, pointing to a very promising approach to design better thermoelectrical materials. In addition, semiconductor nanowire arrays can be used as potential substrates to achieve high energy conversion efficiency in photovoltaics.
27.04.2007 / MF
Prof. Dr. Mark E. Welland
Professor of Nanotechnology, Nanoscience Centre, University of Cambridge, GB
"Using physics to quantify aspects of Alzheimer's and related human diseases"
22.05.2006 / MF
Prof. Dr. Tom Lubensky
Department of Physics and Astronomy, University of Pennsylvania, USA
"Phases, Fluctuations, and Dynamics of Rigid and Semi-flexible Rods"
Rigid rods provide a usefull theoretical idealization for the study of rotational dynamics and the formation of ordered liquid crystalline phases. Today, there are a variety of physical realizations of rigid rods, including various filamentous viruses, carbon nanotubes, and engineered ellipsoids, that can be dispersed in water. In addition, there are a wide variety of biopolymers like actin and neurofilaments that are effectively rigid up to a persistence length, which can be as long or longer than the polymers themselves.
This talk will review some of the properties of dispersions of rigid rods. It will then discuss several recent experiments, and related theory, on colloidal systems of rigid and semi-flexible polymers, including ones on nematic carbon nanotube gels and fluctuations of polymers in a nematic background. In celebration of the 100th anniversary of Einstein's 1906 paper introducing the concept of rotational Brownian motion, it will discuss in detail recent experiments by the Penn group on coupled translational-rotationsl Brownian motion of rigid rods and interpret them in terms of a Langevin theory originally developed by F. Perrin. Finally it will use these results to discuss the dynamics of a chiral granular gas.
13.10.2005 / FKF
Prof. Dr. Bengt I. Lundqvist
Chalmers University of Technology, Göteborg, Department of Applied Physics
"Promising Path to Understand Sparse Matter using ab-initio Calculations"
The wide world of sparse matter seems now accessible to a description by density-functional theory. To understand biostructures, soft matter, and other abundant sparse systems we must account for both strong local atomic bonds and weak nonlocal van der Waals (vdW) forces between atoms separated by empty space. To this end, a fully nonlocal functional has recently been developed. Applications to a diverse set of systems including layered compounds, dimers of benzene, doped benzene and cytosine, and polymer crystals, shows that this approach is very promising. This could have great ramifications.
07.07.2005 / FKF
Prof. Dr. Yoshinori Tokura
The University of Tokyo, School of Engineering, Department of Applied Physics
"Materials Design for Gigantic Response with Correlated Electrons"
21.04.2005 / MF
Prof. Dr. Benjamin Geiger
Departments of Molecular Cell Biology and Structural Biology, The Weizmann Institute of Science, Rehovot, Israel
"Exploring the environment: mechanisms underlying cellular navigation"
28.09.2004 / FKF
Dr. Phedon Avouris
IBM Research Division, T.J.Watson Research Center
"Carbon nanotube electronics and optoelectronics"
03.06.2004 / MF
Prof. Dr. Frans Spaepen
Division of Engineering and Applied Sciences, Harvard University, Cambridge, USA
"Energies in Materials Science"
08.05.2003 / FKF
Dr. Don Eigler
IBM Almaden Research Center, San José, California
"Molecule cascades: Nanometer-scale architectures that compute"
The scanning tunneling microscopy (STM) can be used to build atomically-precise structures and investigate their physical and functional properties. I will present a new class of nanometer-scale structures, "molecule cascades", that are both instructive – they enable detailed studies of adsorbate motion, and functional – they do computation.