Hong Y. Ling, Professor

Department of Physics and Astronomy

Rowan University

Glassboro, New Jersey 08028

(856) 256-4342

ling@rowan.edu

 

 

Ph. D. Drexel University

Field: Theoretical atomic, molecular & optical physics (AMO) and condensed matter physics.

Click here to see my Publications.

 

Atoms, like elementary particles, can be classified into bosons and fermions whose behavior are governed by two very different statistics while there is no limit to the number of bosons each quantum state can share, no two fermions can occupy the same quantum state, a rule known as the Pauli exclusion principle. It has been known for more than half century that depending on whether they are bosons or fermions or mixtures of both, atomic gases (or liquids) can exhibit different but equally fascinating quantum effects at the macroscopic level that are of fundamental interest across broad spectrum of physics, especially within the disciplines of condensed matter and nuclear physics. As most substances in nature solidify before the temperature could reach the regime where macroscopic quantum nature of gas can be manifested, experimentally accessible samples of quantum gases have been limited only to a few isotopes such as 3He and 4He, until recently when the rapid technological advancement in cooling and trapping of neutral atoms has completely turned the situation around. The list of possible quantum gases under this new technology seems endless in view of the rich existence of atomic elements and their isotopes in nature. Further, new systems are often of multi components in nature, e.g., a spinor condensate where population can be exchanged among Zeeman sublevels of a same hyperfine state, and a coupled atom-molecule condensate where atoms can be combined into molecules either by photo-association or magneto-association (also known as the Feshbach resonance). An important feature is that with ultracold atomic gases, key system parameters, including the interaction between particles of same and different species, can be tuned precisely, thereby allowing the low-temperature physics to be explored in a well controlled manner, in regimes possibly far beyond the reach by typical solid state systems. It is of no surprise that recent years have witnessed a dramatic rise of the interest, by physicists from many disciplines, in the study of ultracold quantum gases, a rapidly emerging field interdisciplinary both to AMO and to condensed matter physics.

 

The primary focus of my current research is on the multi-component quantum gas containing both atomic and molecular species in which photoassociation or Feshbach resonance serve as the underlying physical mechanism for interspecies population exchange. This atom-atom-molecule gas can exist not only as bose-bose-bose, but also as fermi-fermi-bose or as bose-fermi-fermi mixture, capable of a rich set of intriguing physical phenomena, which have been the main source of inspiration for much recent excitement at the forefront of ultracold atomic physics.

 

One area of interest is to use the model to create the molecular condensate. The road to molecular condensation is complicated by the fact that more degrees of freedom are needed to describe molecules than atoms. As a result, cooling particles by entropy removal, a direct method popular with atoms, has so far proved to be unable to lower the temperature of molecules down to the regime of quantum degeneracy. The new opportunity brought by the atom-molecule condensate system is that when combined with a pair of Raman laser fields, it allows the deeply bound (and hence stable) molecular condensate to be coherently generated by the technique of stimulated Raman adiabatic passage (STRAP). As matter of fact, this has been the path taking virtually by all the current experiments in creating molecular condensate.

 

Another interest is to explore and find ways to differentiate varies exotic phases in the resonant fermi-fermi-bose mixture. In addition to being an ideal system for the exploration of the crossover from a Bose-Einstein condensate (BEC) of highly localized pairs to nonlocal Bardeen-Cooper-Schrieffer (BCS) pairs, the two-component atomic Fermi gas, when operating in the unitarity regime, constitutes a strongly interacting Fermi gas exhibiting a rich set of physics, and therefore serves as a fertile playground for studying exotic phases that may shed light on long-standing problems in many different areas of physics, including high-temperature superconductivity, nuclei, compact stars, quantum chromodynamics, etc..

 

Finally, the coupled atom-molecule systems with stable heteronuclear molecules of large electric dipoles are of particular importance. First, it can be employed to create a stable dipolar quantum gas, which represents a novel state of matter with long-range and anisotropic dipole-dipole interactions that are highly amenable to the manipulation by dc and ac microwave fields. The creation of such a gas holds the promise of greatly spurring activities at the forefront of physics research, particularly with respect to quantum computing and simulation and precision measurement. Second, in the BEC extreme, the fermi-ferm-bose model in which bosons are polar molecules represents a special mixture of quantum gas where due to the anisotropic nature of the dipole-dipole interaction, the effective fermi-fermi interaction mediated by the polar molecules become anisotropic as well, creating opportunities for fermions to undergo unconventional BCS pairings. In the BCS extreme, the same combination serves as an excellent model for studying the effect of fermionic superfludity on the stability of the quantum dipolar gas.