Research Highlights

Some of the biggest questions about our universe may be solved by scientists using its tiniest particles. Since the 1960s, physicists have been looking at particle interactions to understand an observed imbalance of matter and antimatter in the universe. Much of the work has focused on interactions that violate charge and parity (CP) symmetry. This symmetry refers to a lack of change in our universe if all particles’ charges and orientations were inverted. “This charge and parity symmetry is the symmetry that high-energy physicists say needs to be violated to result in this imbalance between matter and antimatter,” explained JILA research associate Luke Caldwell. To try to find evidence of this violation of CP symmetry, JILA and NIST Fellows Jun Ye and Eric Cornell, and their teams, including Caldwell, collaborated to measure the electron electric dipole moment (eEDM), which is often used as a proxy measure for the CP symmetry violation. The eEDM is an asymmetric distortion of the electron’s charge distribution along the axis of its spin. To try to measure this distortion, the researchers used a complex setup of lasers and a novel ion trap. Their results, published in Science as the cover story and Physical Review A, leveraged a longer experiment time to improve the precision measurement by a factor of 2.4, setting new records. 

In a new paper published in Physical Review Letters, JILA and NIST Fellows Eric Cornell, Jun Ye, and Konrad Lehnert developed a method for measuring a potential dark matter candidate, known as an axion-like particle. Axion-like particles are a potential class of dark matter particle which could explain some aspects of galactic structure. This work is also a result of collaboration with Victor Flambaum who is a leading theorist studying possible violations of fundamental symmetries. 

New research from the Cornell Group suggests that the van der Waals universality may have limitations.

Why are we here? This is an age-old philosophical question. However, physicists like Will Cairncross, Dan Gresh and their advisors Eric Cornell and Jun Ye actually want to figure out out why people like us exist at all. If there had been the same amount of matter and antimatter created in the Big Bang, the future of stars, galaxies, our Solar System, and life would have disappeared in a flash of light as matter and antimatter recombined.

Newly minted JILA Ph.D. Catherine Klauss and her colleagues in the Jin and Cornell group decided to see what would happen to a Bose-Einstein condensate of Rubidium-85 (⁸⁵Rb) atoms if they suddenly threw the whole experiment wildly out of equilibrium by quickly lowering the magnetic field through a Feshbach resonance.

Newly minted Ph.D. Ming-Guang Hu and his colleagues in the Jin and Cornell groups recently investigated immersing an impurity in a quantum bath consisting of a Bose-Einstein condensate, or BEC. The researchers expected the strong impurity-boson interactions to “dress” the impurity, i.e., cause it to get bigger and heavier. In the experiment, dressing the impurity resulted in it becoming a quasi particle called a Bose polaron.

It took Eric Cornell three years to build JILA’s first Top Trap with his own two hands in the lab. The innovative trap relied primarily on magnetic fields and gravity to trap ultracold atoms. In 1995, Cornell and his colleagues used the Top Trap to make the world’s first Bose-Einstein condensate (BEC), an achievement that earned Cornell and Carl Wieman the Nobel Prize in 2001.

The Cornell and Jin groups have just met the challenge of creating and studying an extremely strongly interacting Bose-Einstein condensate (BEC). This feat was reported in Nature Physics online January 12, 2014. An example of an ordinary weakly interacting Bose-Einstein condensate (BEC) is a quantum gas of rubidium atoms (⁸⁵Rb) all piled up in a little ball whose temperature is a chilly 10 nK.

Physicists wonder about some pretty strange things. For instance, one burning question is: How round is the electron? While the simplest picture of the electron is a perfect sphere, it is possible that it is instead shaped like an egg. The egg shape would look a bit like a tiny separation of positive and negative charges. Physicists call this kind of charge separation an electric dipole moment, or EDM. The existence of an EDM in the electron or any other subatomic particle will have a profound impact on our understanding of the fundamental laws of physics. 

The Jin and Cornell groups have discovered irrefutable evidence for the contact. The contact appears in ultracold gases under conditions when the atoms are close “contact” in a Bose-Einstein condensate, or BEC.  Like pressure, volume, and temperature, the contact is an important property of ultracold ensembles of atoms.  The contact is particularly important when the atoms interact with each other, since the contact tells you how likely it is that an atom in the ensemble is having a close encounter with another atom.

Graduate students or research associates at JILA have the option of signing up to help teach after-school science classes to elementary and middle school students in the St. Vrain School District. The volunteers expect to stimulate the children to learn to think critically, enjoy science activities, and become confident in their own abilities to master difficult concepts. What they may not anticipate at first is that they will learn some important skills themselves, including the ability to communicate scientific concepts in everyday language and, with that new ability, gain a better understanding of education.

A while back, Fellow Eric Cornell started thinking about all the waste heat produced by the use of water to cool refi neries and other industrial plants. In a few places, the waste hot water — at ~212°F — is used to heat commercial and apartment buildings. 

The Anderson and Cornell groups have adapted two statistical techniques used in astronomical data processing to the analysis of images of ultracold atom gases. Image analysis is necessary for obtaining quantitative information about the behavior of an ultracold gas under different experimental conditions. 

The mission to find the electron electric dipole moment (eEDM) recently took a menacing turn. Chief Eric Cornell and his protégés were already hard at work characterizing the hafnium fluoride ion (HfF⁺). Their goal was to be the first in the world to complete the mission. In their choice of molecule, they owed a lot to JILA theorists Ed Meyer and John Bohn (a.k.a. Agents 13 and 86), who had taken the theory world by storm in 2006 when they devised a simple and straightforward method for the evaluation of molecular candidates for an eEDM search.

What happens to a Bose-Einstein condensate (BEC) when its atoms interact strongly? One possibility for large attractive interactions is that the condensate shrinks and then explodes, as the Cornell and Wieman groups discovered in 2001.

In the quantum world inside Fellow Eric Cornell’s lab, communication occurs across a two-dimensional lattice array of Bose-Einstein condensates (BECs) when atoms tunnel out of superatoms (made from about 7000 garden-variety rubidium (Rb) atoms) into neighboring BECs. This communication keeps the array coherent, i.e., the phases of all condensates remain locked to each other. But something interesting happens when the tiny superatoms stop communicating among themselves. Vortices form. And how many appear depends on temperature.

Small changes in the quantum fluctuations of free space are responsible for a variety of curious phenomena: a gecko’s ability to walk across ceilings, the evaporation of black holes via Hawking radiation, and the fact that warmer surfaces can be stickier than cold ones in micro- and nanoscale electromechanical systems (MEMS and NEMS). The tendency of tiny parts to stick together is a consequence of the Casimir force.

Does the electron have an electric dipole moment (eEDM)? If it does, the standard model of elementary particle physics says this dipole moment is many orders of magnitude below what can be measured experimentally. As Fellow John Bohn quips, "It's a darn small one."

Graduate students Dave Harber and John Obrecht, postdoc Jeff McGuirk, and Fellow Eric Cornell recently devised a clever way to use a Bose-Einstein condensate (BEC) inside a magnetic trap to probe the quantum behavior of free space. To do this, the researchers first created a BEC inside a magnetic trap, whose shape (where the condensate forms) resembles a cereal bowl. Then as shown in the diagram to the right, they moved the BEC in the bowl closer and closer to a glass surface until distortions in the shape of the bowl appeared.