News & Research Highlights

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.

A key challenge in developing new nanotechnologies is figuring out a fast, low-noise technique for translating small mechanical motions into reasonable electronic signals. Solving this problem will one day make it possible to build electronic signal processing devices that are much more compact than their purely electronic counterparts. Much sooner, it will enable the design of advanced scanning tunneling microscopes that operate hundreds to thousands of times faster than current models.

Researchers are investigating a new kind of microelectronics called spintronics. These devices will rely on the spindependent behavior of electrons in addition to (or even instead of) conventional charge-based circuitry. Researchers in physics and engineering anticipate that these devices will process data faster, use less power than today's conventional semiconductor devices, and work well in nanotechnologies, where quantum effects predominate. Spin-FETs (field effect transistors), spin-LEDs (light-emitting diodes), spin-RTDs (resonant tunneling devices), terahertz optical switches, and quantum computers are some of the multifunctional spintronic devices being envisioned.

JILA physicists are investigating complex and interesting materials, circuits, and devices based on ultracold atoms instead of electrons. Collectively known as atomtronics, they have important theoretical advantages over conventional electronics, including (1) superfluidity and superconductivity, (2) minimal thermal noise and instability, and (3) coherent flow. With such characteristics, atomtronics could play a key role in quantum computing, nanoscale amplifiers, and precision sensors.

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."

When illuminated by X-ray and infrared light beams in tandem, electrons can tap dance off a platinum surface because they've actually grabbed a photon from both beams simultaneously. As you might have guessed, there is more going on here than the ordinary photoelectric effect, which Albert Einstein explained more than a century ago. In the photoelectric effect, electrons escape from a solid after absorbing a single photon or bundle of light energy. 

What do fermions in atomic nuclei, neutron stars, and ultracold trapped gases have in common? They have the same fundamental behavior. The exciting news is that there's now hard evidence that this is true, thanks to graduate students Jayson Stewart and John Gaebler, Cindy Regal who received her Ph.D. in physics in November, and Fellow Debbie Jin.

"Chemistry is a highly improbable science," says Graduate Student Mike Deskevich, who adds "It's good for life on Earth that things are so unreactive." For instance, if chemical reactions happened easily and often, oxygen in the air would cause clothing and other flammable materials to burst into flame. In addition to making life difficult, high probability chemistry would render theoretical chemical physics much less interesting. As it is, theorists spend months determining the particular molecular shapes, vibrations, and energy states that make the simplest chemical reactions possible.

The breakdown of chlorofluorocarbons (CFCs) in the stratosphere has been implicated in the destruction of Earth's protective ozone layer. Consequently, scientists have undertaken studies to better understand the structure and behavior of highly reactive, but short-lived, free radicals produced during the breakdown process. The molecules, which contain either fluorine or chlorine, are an important source of atmospheric halogen atoms. Elucidating their 3D structure and dynamical behavior will help scientists better understand atmospheric chemistry as well as their fundamental molecular properties.

A solvent is something that dissolves or disperses something else. It's the water in salt water, the alcohol in cough syrup, the lactates or ethers in inks. For many of us, solvents are the background music of the chemistry taking place all around us. But this isn't how Fellow Carl Lineberger and his colleagues in chemical physics think about solvents. Lineberger, Former Research Associate Vladimir Dribinski, Graduate Students Jack Barbera and Josh Martin, and student visitor Annette Svendsen see them as key players in some chemical reactions, right down to the level of quantum mechanical interactions.

Life can be challenging on the biophysics research frontier. Consider gold nanoparticles as a research tool, for example. Gold is ductile and malleable as well as being a good conductor of heat and electricity. Its unique chemistry allows proteins and DNA to be easily attached to these nanoparticles. Physicists have been investigating gold nanoparticles in optical-trapping experiments because they enhance trapping efficiency and potentially increase detection sensitivity.

The fine structure constant is getting a lot of attention these days. Known as α, it is the "coupling constant," or measure of the strength of the electromagnetic force that governs how electrons, muons, and light interact. What's intriguing is that new models for the basic structure of matter predict that α may have changed over vast spans of cosmic time, with the largest variations occurring in the early universe. However, the Standard Model says a has always been the same. Our basic understanding of physics depends on scientists' ability to determine whether or not α is an "inconstant constant."

Imagine trying to describe the intricate motions of a single atom as it interacts with a laser. Then suppose you could generalize this understanding to a whole cloud of similar atoms and predict the temperatures your experimental physicist colleagues could achieve with laser cooling. This way-cool theoretical analysis comes compliments of Graduate Student Josh Dunn and Fellow Chris Greene.

Our lives depend on heme. As part of hemoglobin, it carries oxygen to our tissues. As part of cytochrome c, it helps transform the energy in food into the energy-rich molecule ATP (adenosine triphosphate) that powers biochemical reactions that keep us alive and moving. As part of cytochrome P450, it helps break down toxic chemicals in our bodies.

JILA physicists are collaborating to explore the link between superconductivity and Bose-Einstein condensation (BEC) of fermions at ultracold temperatures. Fermions have an odd number of total protons, neutrons, and electrons, giving them a half integer spin, which is either up or down. At ultracold temperatures, this means fermions can't just occupy the same energy level (like bosons, which have an even number of atomic constituents) and form one superatom in a BEC. Instead, they stack up in the lowest energy states, with two fermions in each state, one spin up and one spin down, forming a Fermi sea.

When molecules smash into each other, things happen on the quantum level. Electrons get shoved around. They may even jump from one atom to another. Spin directions can change. A chemical reaction may even take place. Since it's not possible to directly observe this kind of electron behavior, scientists want to be able to probe it with novel spectroscopies. Now, thanks to a recent theoretical study, ultracold spectroscopy looks particularly promising for elucidating electron behavior during molecular impacts.

One way to understand unstable molecules is to systematically create slightly different versions of a similar stable molecule and investigate each new molecule with identical analysis and experiments. That is exactly what researchers from JILA and CU are doing with a series of ringed molecules.

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.

RNA molecules can perform amazing biological feats, including storing, transporting, and reading genetic blueprints as well as catalyzing chemical reactions inside living cells. To manage the latter feat, RNA molecules must rapidly fold into an exact three-dimensional (3D) shape. Understanding how RNA accomplishes this is a major scientific challenge. Former JILA postdoc Jose Hodak, Christopher Downey (doctoral candidate in Chemistry and Biochemistry), JILA graduate student Julie Fiore, Chemistry and Biochemistry Professor Arthur Pardi and Fellow David Nesbitt are meeting this challenge head on.

Imagine high-school or college students so excited about physics they can hardly wait to get to class every day and learn more about how the world works. Fellow Carl Wieman recently offered cogent suggestions to new physics teachers on coming closer to this ideal. First, he recommended starting with research on how people learn physics and paying particular attention to the concept of "cognitive load." This concept, which posits that people can only process about seven ideas in short-term working memory, sets clear limits on how much information can be effectively introduced in a single lesson (or scientific talk).