Condensed Matter Physics / Materials Research Physics
Congratulations to Prof. Roger Pynn
Winner of the 2009 Gunnar Randers Prize!
His Majesty King Harald V of Norway (left) presents Gunnar Randers Prize to Roger Pynn (Photo: Einar Madsen, IFE)
Condensed matter physics (CMP) is by far the largest field of contemporary physics –by an estimate, one third of all American physicists identify themselves as condensed matter physicists. CMP studies the "condensed" phases that appear whenever the number of constituents in a system is extremely large and the interactions between them are strong. Condensed phases range from normal solids and liquids to the Bose-Einstein condensate found in certain atomic systems at very low temperatures. Other examples include superconducting phase exhibited by conduction electrons in certain materials, or the ferromagnetic and antiferromagnetic phases of electron spins on atomic lattices. CMP is frequently associated with materials research, that is application oriented interdisciplinary field which involves study of the synthesis, properties and structure of a wide range of materials, many of practical or technological importance. The field draws contributions from CMP, chemistry and engineering and, more recently, from biology.
Our research efforts focus on the microscope structure and dynamics of condensed matter through theory and experiments. Areas of study include but are not limited to the following:
- Collective Excitations in Confined Quantum Liquids and Solids
- Porous Materials
- Hydrogen Storage Materials
- Strongly Correlated Spin Systems
- Complex Fluids
- Structural Biology
- Neutron Production and Moderation
- Development of Neutron Scattering Instruments
- Thin Films
Structure factor of high T superconductor
Spin orientation in cuprates
Low dimensional and strongly correlated condensed matter are among the most interesting physical systems being studied today. Among these are high-temperature superconductors, graphene, quantum Hall liquids, dilute ultracold atomic gases, Luttinger liquids, heavy fermion systems, and unconventional quantum magnets.All these systems are studied at IU. Interactions in these systems are typically crucial,often invalidating the basis of simplified descriptions such as Landau-Fermi liquid theory. New mathematical and physical approaches are required to understand and analyze these systems. Often one finds qualitatively new states of matter,with unexpected properties and, occasionally, useful functionalities
(Imagine if you could create a room temperature superconductor!) Even the phase transitions among competing states in such systems, both quantum and classical, may themselves have remarkable properties. In modern condensed matter physics, one often finds that from systems with relatively simple ingredients, surprising and complex behaviors can emerge, so that (paraphrasing Nobel laureate Phil W. Anderson) "the whole is more than the sum of its parts."
Electrodynamics at surfaces
We have set up simulations using the finite-difference time-domain (fdtd) method to solve Maxwell’s equations on a discrete mesh in both space and time. With these codes we can study both far field properties (like reflection, transmission, and absorption) as well as near field properties (like field and current distributions). These studies are being used to design and interpret several current experiments such as 3-D distribution of light intensity transmitted through a circular nanoaperture and transmission of light through a pair of adjacent, circular holes. A different research direction was stimulated by the recent controversy over the behavior of so-called negative index materials. Our approach is to produce movies showing the propagation of a pulse of light as it encounters such material. This allows one to “see” clearly what happens. An example is at http://media4.physics.indiana.edu/~schaich/ajp/mov.1.swf, which shows a wavepacket of light incident along the normal from vacuum onto a slab of negative index material.
Part (a) - sketch of the experimental configuration. SEM for aperture dia. of (b) 110, (c) 200, and (d) 360 nm. Parts (e-g) - 3-D iso-intensity surfaces of the light.
Complex Fluids & Soft Condensed Matter
Chains of ferromagnetic particles in magnetic field and the corresponding SANS pattern
Complex fluids include highly disordered, multi-component systems such as colloids, foams, slurries, emulsions, detergent solutions, lipid membranes or polymer solutions. The typical correlation length scales of the structures formed are in nanometers which lead to enormous interfacial area of the dispersed component that, in turn, predetermines the macroscopic properties of the fluid, e.g. the viscosity. At IU we are studying such questions as how inter-particle interactions influence the dynamics and structure of such fluids.
Neutron Scattering & LENS Project
Layout of LENS
The Low Energy Neutron Source (LENS) is a major asset for conducting condensed matter research at IUCF. When neutrons are scattered from matter, the resulting angular and velocity distributions of the scattered neutrons can be interpreted to determine where atoms are located and how they move. Neutrons interact with matter in a unique manner that allows them to identify hydrogen and other light atoms among heavy atoms, making them very useful for the study of biological macromolecules and man-made polymers, both of which contain substantial amounts of hydrogen. At LENS, neutron scattering will be used primarily to study large-scale (1 -1000nm) structure of materials.
Neutron Scattering & Structural Biology
Because of their unique sensitivity to hydrogen atoms, neutrons can be used to precisely locate hydrogen atoms. Large biological molecules contain numerous hydrogen atoms many of which are crucial for functions such as the enzymatic activity of proteins. Because hydrogen and deuterium (a heavy isotope of hydrogen) scatter neutrons differently, the best way to examine a particular part of a biological macromolecule with neutron scattering is through isotope substitution, i.e. replacing hydrogen with heavy hydrogen (deuterium) atoms. Thus, in a technique called contrast variation, scientists can highlight different types of molecules, such as a nucleic acid or a protein in a chromosome, by substituting deuterium for hydrogen at the interesting sites. This allows them to glean independent structural information on each component within the macromolecular complex. The structures of complex fluids and biomolecular systems both in bulk and as films and membranes, are being studied at IU.
Formation of benzene from acetylene on palladium, revealed in STM* (left and vibrational spectra in electron scattering (right)
Thin and multi-layered films represent prototypical examples of nano-structured materials whose structure and properties can be easily controlled through layer-by-layer growth through vacuum, chemical, or electro-deposition processes. The growth can be used to tune the composition of the material at length scales comparable to the fundamental physical lengths that determine a material's properties. For instance, in the Giant Magnetoresistance (GMR) effect, it is possible to make a magnetic field sensor by separating two magnetic materials by a non-magnetic layer that is thin enough for electrons traveling between the two magnetic layers to maintain memory of their quantum mechanical phase and momentum. The GMR effect has provided a rich variety of phenomena to unravel, and the magnetic recording industry is now completely dominated by GMR technology for its read heads. Researchers at IUCF are interested in such questions as how you can quantify the disorder at interfaces in these materials (and how that disorder is correlated from one interface to the next), as well as how that disorder influences the properties of the material.
TEM of Vicor glass
Studies of the confinement of gases, liquids and solids in porous materials is of great interest both for practical applications, such as oil refinery, ceramics and catalysis, and from a fundamental scientific standpoint. The appearance of new phenomena, ranging from modifications of the structure to the enhancement of quantum effects, arise due to the finite size of the confined system, and the enhanced importance of the interactions with the pore walls.
Structure factor of Xerogel
Liquids and solids adsorbed in porous materials have been of long standing interest since their properties can be significantly different from those of the bulk phase.Confinement induced changes include enhancement of the liquid-vapor transition, suppression of the liquid-solid transition, hysteresis between melting and freezing, modification of the structure of the solid phase and the elimination or introduction of solid phases.