1994 McCoy Award Recipient
Anant K. Ramdas and Sergio Rodriguez
Professors of Physics
Anant K. Ramdas and Sergio Rodriguez, both professors of physics, are condensed matter physicists. Their research interests are directed toward the discovery, delineation, and understanding of solid state phenomena using optical - in particular spectroscopic - techniques. Their research has focused on the physics of semiconductors and their heterostructures. While Anant Ramdas is an experimenter who employs a wide range of spectroscopic techniques, Sergio Rodriguez is a theoretical physicist who uses quantum mechanics, symmetry principles, and other theoretical techniques to obtain insights into physical phenomena. Anant Ramdas and Sergio Rodriguez have collaborated extensively over the years on a wide range of research topics in semiconductor physics. Anant Ramdas received his undergraduate and graduate education in India, obtaining his Ph.D. in 1956 from the Raman Research Institute as a student of Professor C.V. Raman; he joined Purdue the same year. In 1977, he received the Alexander von Humboldt Senior U.S. Scientist Award. In 1994, the American Physical Society awarded him the Frank Isakson Prize and in 1993 the Indian Academy of Sciences appointed him to the Raman Professorship. Sergio Rodriguez received his undergraduate and graduate education from the University of California, Berkeley, where he obtained his Ph.D. in 1958 working with Professor Charles Kittel. He joined Purdue in 1960. In 1967 he received a John Simon Guggenheim Fellowship and in 1974 the Alexander von Humboldt Senior U.S. Scientist Award. He was awarded Fulbright Fellowships in 1978 and 1990.
Semiconductors such as elemental silicon and germanium are prototypes of crystals grown with unprecedented perfection, whose properties can be impressively manipulated in a flexible manner by the deliberate introduction of specific impurities. They are model systems in which many fundamental issues in condensed matter physics can be addressed under well-characterized conditions: How are electronic levels modified when atoms condense to form crystals? How do the atoms of a crystal vibrate? What is the nature of an imperfection - a chemical impurity - in an otherwise perfect crystal? What is the nature of the localized and collective excitations of the atoms, magnetic ions, and electrons in such crystals? These questions have led to numerous novel physical phenomena discovered through the application of spectroscopic techniques. Theoretical formulation of the physical principles underlying these phenomena have provided deep insights into concepts unique to condensed matter. Applications in solid state electronics, infrared sensors, and optoelectronics have originated in the basic understanding of semiconductors and constitute major factors in their appeal for current research. In recent years, ultrahigh vacuum techniques have been ingeniously employed in the fabrication of submicron layers of semiconductors deposited on substrates. A juxtaposition of such layers of different semiconductors leads to semiconductor, heterostructures that possess novel properties without counterparts in their bulk form. These structures are called 'quantum well structures' or 'superlattices.' A new generation of optoelectronic applications based on such structures has transformed solid state electronics. Ramdas and Rodriguez have investigated how charge carriers are bound to chemical impurities in semiconductors. Spectroscopic studies demonstrate that the charges thus bound to Coulomb centers are solid state analogs of the hydrogen atom, amenable to rigorous theoretical analysis and precise experimental investigations. Novel effects of reduced dimensionality in quantum well structures and superlattices as reflected in their electronic and vibrational excitations have been discovered by Ramdas and Rodriguez. The introduction of magnetic ions in semiconductors results in the formation of diluted magnetic semiconductors; their experimental and theoretical investigations form a major focus of the joint research of Ramdas and Rodriguez. Novel isotope related phenomena in semiconductors discovered by Ramdas and Rodriguez in recent years form the subject of their McCoy Lecture.