Chris Greene - 2020 Herbert Newby McCoy Award

Chris Greene – 2020 Herbert Newby McCoy Award

Herbert Newby McCoy Distinguished Lecture

Strengthening our theoretical understanding of the quantum world involves both detailed quantitative computations of the relevant equations, and an enhancement of our qualitative intuition. This strategy has enabled the Greene group's discovery of new phenomena, such as the “trilobite molecule” and the interpretation of puzzling experiments.

Biography

Chris Greene earned his undergraduate BS in physics and mathematics from the University of Nebraska, and his Ph.D. from the University of Chicago. Following a one-year postdoctoral stint at Stanford, he held faculty positions at Louisiana State University and the University of Colorado before joining the Purdue faculty in 2012. He is currently the Albert Overhauser Distinguished Professor of Physics and Astronomy. He has received two prizes from the American Physical Society, namely the inaugural I. I. Rabi Prize and the Davisson-Germer Prize. He has also received the the Hamburg Prize for Theoretical Physics, and was elected to the U.S. National Academy of Sciences in 2019.

Over his career, Greene has mentored 26 postdocs and 26 completed Ph.D. students, two of whom received the annual Thesis Prize awarded by the Division of Atomic, Molecular and Optical Physics of the American Physical Society. With his students, postdocs and other collaborators, he has published more than 350 refereed articles, including more than 50 in the journal Physical Review Letters. His articles have been cited in the literature more than 14,000 times.

Making the Counterintuitive Intuitive in the Quantum World

Abstract

The bizarre nature of quantum mechanical phenomena might seem too counterintuitive, from the perspective of daily life, to ever yield qualitative insights. Yet by diving deep into the quantum world, developing theory to describe experiments that confirm the basic correctness of our quantum mechanical techniques, this research not only demonstrates the confirmation of theory and experiment, but also showcases a deepening of our intuition and our ability to predict new phenomena. Much of the progress in Greene's research group, both quantitatively and qualitatively, has derived from advancing a theoretical toolkit that identifies a single degree of freedom in the problem to treat adiabatically, i.e., evolving slowly. This lecture will show examples of how use of this simple theoretical idea can address issues across a broad range of scientific problems in condensed matter physics, atomic and molecular physics, and nuclear physics. As one illustration, he will describe his group's recent theoretical prediction of a way to create a ghost chemical bond.

Research Accomplishments

Greene and his collaborators have developed novel theoretical methods for solving challenging quantum mechanical problems, especially in atomic, molecular and optical physics, but with applications in other physics subfields as well. This research effort has provided the first explanation of some experimental results that were not previously understood, and it has also predicted phenomena such as new types of quantum states that have subsequently been detected in experiments. The following is a selection of some of the major contributions:

• Developed a theoretical formulation to predict the loss rate of atoms from a quantum gas caused by three-body recombination at ultracold temperatures, including the role of the bizarre so-called Efimov states.

• Predicted a novel class of ultra-long-range trilobite molecules that are bound together by a single highly excited Rydberg electron, which by now have been observed by multiple experimental groups.

• Extended adiabatic hyperspherical coordinate theory from atomic and molecular physics to yield insights into systems of interest in condensed matter and in nuclear physics, namely in connection with the fractional quantum Hall effect and the four-neutron problem.

• Established the connection between asymmetrical spectral line shapes in photoabsorption by any system and the phase of oscillation created by an ultrafast laser pulse excitation of the same system.

• Developed a new way to solve the complex quantum mechanical problem of a low energy electron that efficiently destroys a symmetrical polyatomic molecule such as the triatomic hydrogen ion, a process important for the astrochemistry of interstellar clouds.