These are exciting times for computational and quantitative biology. Amazing amounts of information have been gathered about genes, about proteins and their interactions with each other, about DNA-protein interactions, about gene expressions, about metabolic and regulatory networks, about development and pattern formation. Synthesizing this information and combining it with the basic principles of physics and statistical mechanics could produce tremendous advances in medical and genetic technologies. It could also lead to a qualitatively new level of understanding of the meaning of life itself from a physicist's perspective--a perspective that asserts that the world we see around us can ultimately be understood in terms of the atoms and molecules making it up.

We are interested in various aspects of such studies, including physical properties of individual biomolecules, cooperative properties of biomolecules such as aggregation and complex formation, and abstract representations of biomolecular interactions and dynamics.

One of the most exciting areas of research in condensed matter physics in recent years is high temperature superconductivity. Superconductivity is a very subtle phenomena. It is a distinct phase of matter that exhibits, besides zero resistance or infinite conductivity ( from which the name superconductor is derived), a number of truly dramatic properties. Perhaps the most intriguing is the fact that it shows quantum mechanical behavior on a human scale. These quantum interference properties can be used to make very sensitive detectors of electromagnetic fields. This is just one of many technological applications of superconductivity. One difficulty with superconductivity, which has prevented it from becoming even more useful for applications, is that it occurs at very low temperatures (typically below 5 degrees K). Recent discovery of superconductivity in Copper Oxide based ceramic materials, above 100 degrees K, may allow us to overcome some of these limitations.

Understanding the phenomenon of superconductivity has occupied some of the best minds of our times. The conventional theory of Bardeen, Cooper and Schrieffer is a landmark in the study of theoretical physics. It took almost half a century for theoretical physicists to develop a comprehensive understanding of this phenomena in simple metals. The burning question today is what makes the Copper Oxide based ceramic materials superconducting at much higher temperatures. It is widely believed that clues to the answer may lie in the nearby insulating magnetic phases and in the fact that as a metal, above the superconducting transition temperature, these materials behave in a very unusual way. Thermodynamic and transport properties of most metals can be described quite adequately in terms of nearly free conduction electrons. Such a picture appears to break down in these materials. When prepared at stochiometric compositions, these materials are insulating and magnetic, although textbook chemistry arguments would lead one to expect a metal. Even as metals, which is obtained off stoichiometry, they are poor conductors and show a lot of residual magnetic behavior.

Our work has focused on understanding the magnetic properties of the insulating parent phase and the abnormal properties of the metallic phase. Theoretical modeling of these phases raises profound questions about the nature of elementary excitations in many-particle systems and leads one to reexamine the very basic properties that differentiate metals and insulators. These studies are intellectually very demanding and require bringing together diverse analytical, numerical and computational techniques. Today, despite much effort, there remain many unresolved questions about these materials and their models.

One of the central themes in our understanding of macroscopic systems is that they exist in a few distinct thermodynamic phases, which are characterized by different symmetries. One interesting idea that has surfaced in various theoretical studies of high temperature superconductivity is the possibility of unusual superconductivity, which differs from the conventional one in terms of its basic symmetries. Whether Copper Oxide superconductors are indeed unconventional in this sense is currently a matter of extensive investigations.

In addition to high temperature superconductivity, we are also interested in the broader question of characterizing and understanding different thermodynamic phases and phase transitions in condensed matter systems.

Honors and Awards
for
Rajiv R.P. Singh

Memberships
  • American Physical Society

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    E-mail singh@physics.ucdavis.edu

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