Five physicists elected Fellows of the American Physical Society

Five physicists at Penn State have been elected Fellows of the American Physical Society (APS): John Collins, distinguished professor of physics; Vincent Crespi, professor of physics and of materials science and engineering; Paul Sommers, professor of physics and of astronomy and astrophysics; David Weiss, professor of physics; and Xiaoxing Xi, professor of physics and of materials science and engineering. The society is the largest physics organization in the world and publishes a wide range of research journals. The APS Fellowship Program recognizes members who have made advances in knowledge through original research and publication, have made significant and innovative contributions in the application of physics to science and technology, or who have made significant contributions to the teaching of physics or to service opportunities and activities of the society. Each year the society elects no more than one-half of one percent of its then-current membership to the status of Fellow in the American Physical Society.

A theoretical physicist, Collins was elected a Fellow for his seminal contributions to the foundation of the theory of strong nuclear interaction in elementary particles, known as quantum chromodynamics (QCD).  He has played a vital role in formulating and proving many of the mathematical results that underlie QCD calculations.  Without the aid of these results, it would not be possible to interpret experimental data produced by modern high-energy particle accelerators or to use the accelerators to search for new phenomena. The result is that these accelerators now can be used, in effect, as microscopes to probe fundamental physics at distance scales on the order of a hundredth or a thousandth the size of a proton.

Crespi was named a Fellow for his creative ideas and innovative computations that enhance understanding of nanoscale matter and that predict new structures and materials with properties possessing technological and/or fundamental scientific value. Crespi is a theoretical physicist whose research is aimed at developing a broad framework of knowledge in condensed-matter physics. He focuses on novel semiconductors, structural energies of materials, electron transport, and superconductivity. Among the applications he is interested in are novel carbon-tubule-based nanodevices that are one-billionth of a meter in size.  He is studying their synthesis, mechanical properties, and electronic structures, including certain mechanical deformations that have a powerful influence on the semiconducting bandgap.

Sommers was elected a Fellow for his significant contributions to experimental cosmic-ray physics, for his major part in designing and building the Pierre Auger Cosmic Ray Observatory, and for his leadership role in using the observatory to obtain novel and important insights into the nature and properties of the highest-energy cosmic rays. The Pierre Auger Cosmic Observatory is an array of cosmic-ray detectors located in a remote part of Argentina. The observatory was built to decipher the messages carried by the highest-energy cosmic rays. These ultrahigh-energy cosmic rays offer a new window for observing extreme processes at work in the universe. Sommers also was an early advocate of combining air-fluorescence detectors with the instrument's giant surface-detector array. He led the team that developed the fluorescence detectors during the design and prototype phases of the observatory.

Weiss was named a Fellow for his seminal contributions to laser cooling, precision measurements, the study of atoms in optical lattices, and for the experimental implementation of one-dimensional gases.  Weiss's research involves experiments with laser-cooled atoms in optical lattices and other light traps. He uses cold, trapped atoms to make precise measurements of fundamental constants and to test fundamental symmetries. He also uses these atoms as model systems to address issues in atomic physics, condensed-matter physics, quantum mechanics, and statistical mechanics.

Xi was elected a Fellow for his extensive and seminal contributions to the science and applications of thin-film materials including high-temperature superconductors, ferroelectrics, and magnesium diboride. Xi's research concerns the materials physics underlying the applications of metal-oxide thin films; in particular, nanoscale-sized thin films. Xi focuses on understanding fundamental electrical, optical, and magnetic properties of these thin films and the effects on them of structural and interfacial defects. He uses the pulsed-laser deposition technique to fabricate oxide thin films and heterostructures. His research group developed a Hybrid Physical-Chemical Vapor Deposition (HPCVD) technique for epitaxial magnesium-diboride thin films.