Condensed Matter Physics Research
The principal goal of materials science is to understand, and predict, just what properties will result from the combination of particular types of atoms into bulk matter. Condensed matter research at UT draws on the strength of renowned experimentalists and theorists to solve these puzzles.
Other useful Web sites include the Correlated Electron Materials Group based at ORNL and the Correlated Electrons Group.
Theory |
Experiment |
Elbio Dagotto |
|
Adolfo Eguiluz |
|
Stephen Nagler (adjunct) |
|
David Singh (adjunct) |
Jian Shen (adjunct) |
Zhenyu Zhang |
|
|
Thomas Callcott |
PROGRAM OVERVIEW
EXPERIMENT:
The experimental group includes Pengcheng Dai, Norman Mannella, Stephen Nagler, Jian Shen, James Thompson, Hanno Weitering, and Professor Emeritus Thomas Callcott.
Dr. Dai uses neutrons as probes to study strongly correlated electron systems. His interests include the microscopic origin of high-transition temperature (Tc) superconductivity, magnetism and electron-lattice coupling in high-Tc superconductors. He also studies magnetism and lattice effects in colossal magnetoresistance (CMR) manganese oxides as well as quantum criticality in Ru-based oxide materials and other transitional metal oxides. [Dr. Dai's Group Page]
Dr. Mannella's research interests are focused on the study of electron correlations and the mechanisms of the interactions among different degrees of freedom in complex electron systems such as, for example, high temperature superconductors, colossal magnetoresistive manganites, thermoelectric materials and transition metal oxides. These studies are typically carried out by means of spectroscopic and structural probes in the soft x-ray regime currently available at third-generation synchrotron radiation facilities, including angle resolved photoemission spectroscopy (ARPES), x-ray absorption spectroscopy (XAS), soft x-ray emission spectroscopy (XES) and resonant inelastic x-ray scattering (RIXS). [Dr. Mannella's Page]
Dr. Nagler's research focuses on understanding cooperative phenomena in novel materials. The primary tool for this work is neutron scattering, using facilities at Oak Ridge National Laboratory and other locations. He also experiments with X-ray scattering using synchrotron radiation to investigate problems such as nonequilibrium ordering kinetics associated with phase transitions.
Dr. Shen is with the Low-Dimensional Materials Physics Group at Oak Ridge National Laboratory. Their work focuses on exploring physical properties of materials in reduced dimensionality, often at nanoscale dimensions, where changes in physical properties are anticipated due to confinement effects either quantum in nature or resulting from surface or interface effects.
Dr. Thompson studies high temperature and conventional superconductors, especially their characterization and modification by tailored defects. He maintains an active collaboration with scientists in the Solid State Division at Oak Ridge National Laboratory, the IBM Watson Research Center, and a number of other international laboratories. He also investigates the property of novel materials. [Dr. Thompson's Page]
Dr. Weitering, another University-ORNL Joint Faculty member, studies the synthesis, structure, electronic structure, transport- and magnetic properties of low-dimensional materials such as quantum wires, surfaces, interfaces, and thin film materials including multilayers and superlattices. He also has research interests in correlated electron systems, cooperative phenomena, phase transitions. Specific techniques in his program include scanning-probe microscopy, electron spectroscopy, molecular beam epitaxy, and in-situ electrical transport measurements. [Dr. Weitering's Group Page]
Dr. Callcott and his collaborators use The Advanced Light Source at Lawrence Berkeley National Laboratory and soft X-ray fluorescence (SXF) spectroscopy to probe the electronic structure of solids. SXF studies are particularly valuable for the investigation of the electronic properties and bonding of complex solids. They provide selective information for each element of the materials, and for each angular momentum state, a property related to the angular distribution of the electrons about the atom. In addition, X-ray excitation simplifies complex spectra and reduces background radiation so that minor elements can be detected in much lower concentrations. These characteristics have made SXF spectroscopy useful in a wide variety of basic and applied studies of metals; alloys; and semiconducting, superconducting, and insulating compounds. An exciting prospect for the future is the study of impurities, clusters, and buried layers, including the investigation of biologically active metal complexes in organic systems. [Dr. Callcott's Page]
THEORY:
The condensed matter theory group consists of Distinguished Professor Elbio Dagotto, Adolfo Eguiluz, Adriana Moreo, John Quinn and Zhenyu Zhang. Working with the Solid State Division of Oak Ridge National Laboratory, the theory group has developed collaborations with other ORNL experimental and theoretical groups. The overall research program is quite diverse, and covers most of the major research topics in condensed matter theory. Although each professor has developed a distinctive research program, there is much overlap of interests among group members.
Dr. Dagotto studies models for Strongly Correlated Electrons, mainly using computational techniques such as the Monte Carlo and Lanczos methods, and several others. The focus in recent years have been on the analysis of the physics of High Temperature Superconductors and Colossal Magnetoresistance Manganites, as well as other materials of the transition metal oxide family. In addition, work in the context of Complexity in Correlated Electrons has recently started, showing that these hard compounds have a soft electronic component. Moreover, the expertise gathered in the study of correlated systems has been recently transfered to the analysis of transport in nanostructures where these correlations play a fundamental role, such as in quantum dots and small molecules. Near future developments include the study of time dependent Density Matrix Renormalization Group techniques to analyze transport in the presence of a finite bias voltage. In the area of low-dimensional electronic systems, the emphasis will be on the influence of phonons and quenched disorder on the properties of the system. The web page of Dr. Dagotto's group is at http://sces.phys.utk.edu/. Dagotto is also part of the Theory Group at the Condensed Matter Sciences Division of Oak Ridge National Laboratory, and his group will soon be located at the Spallation Neutron Source, next to the ORNL Nanocenter.
Dr. Eguiluz does calculations on many-body excitations in real metals. He calculates collective response systems using actual wave functions for metals. These computationally intense methods require parallel codes on vectorized computers. He also keeps abreast of recent advances in many-body theory, an interest he shares with Dr. Quinn.
Dr. Moreo has focused her research on the study of systems of Strongly Correlated Electrons, using a variety of many-body techniques including the use of computational methods. She recently introduced a phenomenological model to study High Temperature Superconductors, that captures the generation of stripes as observed experimentally. Recent efforts have included phonons in the simulations. Previous work also addressed the physics of CMR manganites and several spin systems. Currently she is devoting part of her time into the analysis of charge transport in correlated nanoscale systems. Her research web page is located at http://sces.phys.utk.edu/. She is also part of the Theory Group at the Condensed Matter Sciences Division of Oak Ridge National Laboratory, and her group will soon be located at the Spallation Neutron Source, next to the ORNL Nanocenter.
In addition to many-body theory, Dr. Quinn's interests encompass electronic structure, electron-electron and electron phonon interactions, superconductivity, magnetism, transport properties, nanostructures, magnetic semiconductors, strongly interacting two dimensional systems, quantum phase transitions, quantum Hall effect, composite Fermions, and collective excitations. [Dr. Quinn's Page]
Dr. Zhang's research areas are in theoretical condensed
matter physics, surface physics, and materials science. He uses a variety
of theoretical/computational approaches to investigate various surface
dynamical phenomena and fundamental mechanisms of pattern formation and
thin film growth.