Rutgers University Department of Physics and Astronomy

2000-01 Handbook for Physics and Astronomy Graduate Students

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Research Programs

Theoretical Condensed Matter Physics

The Rutgers faculty in condensed matter theory have interests spanning many areas including: Highly-correlated electron phenomena, such as high-temperature superconductivity, magnetism and heavy-fermion physics; physics at surfaces, including dynamic phenomena and electronic and geometrical structure; quantum liquids; equilibrium and non-equilibrium statistical mechanics; first principles calculations of electronic and structural properties; phase transitions and critical phenomena; semiconductor physics; quantum statistical mechanics and field theory; thermodynamics, transport and localization in disordered systems. At Rutgers, there is also a strong mathematical physics effort centered primarily on rigorous results in statistical mechanics and quantum field theory.

Professor Elihu Abrahams

My research activities are in theoretical condensed matter physics. My main interests concern the quantum-mechanical many-body problem in the presence of very strong particle-particle interactions. In this area, I have been using the techniques of quantum statistical mechanics and field theory to investigate the phase transitions and the transport and thermodynamic properties of a number of systems, including high-temperature superconductors, metals at the threshold of breakdown of Fermi-liquid behavior, helium at ultra-low temperatures, localized spins in metals, magnets with unusual spin correlations, and excitons in semiconductors.

Professor Natan Andrei

My research interests are in the areas of particle physics and condensed matter physics. In the former I am studying the relations between conformal and integrable field theories as well as formulations of string theories on loop space. My condensed matter interests center around strongly correlated electronic systems, in particular High Tc superconductors, heavy fermion compounds and quantum Hall systems.

Professor Kieron Burke (Chemistry)

My research is aimed at understanding the electronic structure of condensed matter, in the form of atoms, molecules, and solids. I develop and apply density functional theory, the most practical method for solving this many-body problem. Recently, I have ventured into time-dependent phenomena, and the interaction of matter with lasers. Applications are in the fields of solid-state physics, quantum chemistry, optical physics, nanoscience, and surface science.

Professor Piers Coleman

My research is concerned with the fundamentally new classes of collective condensed matter behavior that emerge in complex materials. Recently, I have been particularly interested in new types of metallic behavior, so called "non Fermi liquid" physics, that develop in the heavy fermion and cuprate metals, together with the unusual magnetic and superconducting phases, they give rise to. Novel magnetism, the possibility of "odd-frequency superconductivity", Kondo insulators and the transport properties of cuprate superconductors are examples of areas of my recent research activity.

Professor George K. Horton

We have been exploring the Feynman path integral formulation of statistical mechanics. For a crystal that leads to a classical partition function, using the Peierls variational principle, with all quantum effects contained in an effective potential. This treatment makes it possible to use powerful, modern versions of simulations such as Monte Carlo and molecular dynamics to study both static and dynamical properties of quantum crystals. ferroelectrics, alkali halides and alkaline earth oxides, e.g. MgO, throughout the phase diagram. Much of this work is supported by the Illinois and San Diego supercomputer centers using their massively parallel machines such as the Thinking Machines' CM5 computer.

Professor Lev Ioffe

My research is in theoretical condensed matter physics. I am mostly interested in problems in the following areas: (1) Strongly interacting electron systems, in particular, a possibility of non-Fermi liquid states in such systems and a theory of a metal- insulator transition; (2) Novel magnetic states as displayed by strongly frustrated materials; (3) Theory of spin glasses, in particular a theory of aging; (4) Flux states in disordered superconductors: flux lattice melting and pinning. I investigate these problems using the techniques of quantum statistical mechanics and field theory.

Professor Gabriel Kotliar

We apply methods of quantum statistical mechanics quantum field theory and computational physics to treat fundamental problems in material science and condensed matter physics. My main interest in the area of disordered and strongly interacting electronic systems. Problems of current interest include the metal-insulator transition in doped semiconductors, the physical properties of transition metal oxides and the phenomena of high temperature superconductivity, the non linear optical properties of artificially fabricated semiconductor systems and the anomalous non equilibrium phenomena in glasses.

Professor David Langreth

Current work in surface physics involves 1) dynamic phenomena including non-adiabatic charge transfer at surfaces, energy transfer in atom-surface scattering, and the theory of vibrational line shapes; 2) structural properties using ab initio electronic structure calculations, and 3) development of approximate methods for determining the long and short range interaction between a surface and an atomic species outside it. The long range goal of a good part of the surface work is to understand in principle how to treat situations where the electrons cannot be assumed to follow adiabatically the motions of the nuclei. It is typical that both the methods of many-body theory and quantum statistical mechanics as well as numerical computations are used.

Professor Paul Leath

My recent research interests have been in the area of breakdown phenomena in disordered materials, e.g. brittle fracture, electrical breakdown, and the critical current in superconductors. Most recently, we have studied the crossover from tough to brittle fracture in heterogeneous and composite materials by both analytic and numerical simulation techniques. I have also explored the role of vortex line creation at defects and their subsequent motion on the behavior near the critical current in superconducting arrays of Josephson junctions. For many years, I have also been interested in phenomena near percolation threshold, where rigidity fails and the elastic constants go to zero even though the material is still connected. Also, I have plans to work again on phonons and spin wave excitations in disordered materials.

Professor Andrei Ruckenstein

My recent interests involve two general areas. The first is concerned with the many-body theory of strongly correlated systems, with emphasis on models of the high-Tc oxides, many-body effects, and the metal-insulator transition in doped semiconductors, the nature of itinerant magnetism, and the physics of heavy fermion systems. The second area of interest is that of coherent phenomena in quantum gases, such as spin-polarized excitons in germanium or spin-polarized atomic hydrogen.

Professor Joseph Sak

My work has been mostly in the area of many body theory. Some examples are: 1) Critical phenomena in liquid crystals. We use renormalization group to study the phase transition between isotropic and nematic phases, especially in the neighborhood of the Landau point at which isotropic oblate, prolate and biaxial phases all coexist. 2) Many body effects in the optical absorption of metals. We study the effects of dynamical screening of the excitonic interaction. This screening shows singularities of the type "infrared catastrophe" which also appear in the self-energy studied previously. However, to have a consistent theory, all singularities must be included simultaneously.

Professor Michael Stephen

My research is mainly concerned with the thermodynamic and transport properties of disordered systems. Examples of such systems are disordered magnets, percolating systems, disordered conductors (classical and quantum mechanical), superconductors, and superfluids. Currently I am working on (1) the quantum tunneling of vortices in disordered superconductors and superfluids, (2) propagation and diffusion of light in a disordered medium near the mobility edge, and (3) diffusion of a passive scalar in a turbulent medium.

Professor David Vanderbilt

In recent years, it has become possible to carry out first-principles calculations of electronic and structural properties of solids with good accuracy using only the atomic numbers of the atoms and some initial guess at atomic coordinates as input. My interests are in applying such methods to study a variety of systems, including structural phase transitions in ferroelectric materials, dielectric properties of oxides, and structure at surfaces and interfaces. I am also involved in the development of novel algorithms and methods (e.g., for computing electric polarization, for constructing pseudopotentials, and for advancing the theory of Wannier functions).

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Revised November, 2000