News & Highlights

In everyday life, conductors are materials that conduct electricity. These materials are used to make metallic wires that carry electricity into our homes.  In contrast, insulators, which don’t conduct electricity, surround these wires in our plugs so we don’t get electrocuted plugging in our computers, appliances, and lights. The difference between a conductor and an insulator is often the amount of disorder, or impurities, present in an electronic material. If such disorder exceeds a certain threshold, the impurities can actually stop electron flow and turn a conductor into an insulator, all because of a phenomenon known as localization.

In 2013, the Cornell and Jin groups created and studied an extremely strongly interacting Bose-Einstein condensate (BEC) of rubidium atoms (⁸⁵Rb). This BEC was short lived and far out of equilibrium. At the time the experimentalists wondered if this new BEC could be a quantum liquid because the quantum mechanical waves of these puffed-up atoms were rubbing up against each other and sliding past one another—like atoms do in liquids we are familiar with in everyday life.

Dynamical phase transitions in the quantum world are wildly noisy and chaotic. They don’t look anything like the phase transitions we observe in our everyday world. In Colorado, we see phase transitions caused by temperature changes all the time: snow banks melting in the spring, water boiling on the stove, slick spots on the sidewalk after the first freeze. Quantum phase transitions happen, too, but not because of temperature changes. Instead, they occur as a kind of quantum “metamorphosis” when a system at zero temperature shifts between completely distinct forms.

New theory describing the spin behavior of ultracold polar molecules is opening the door to explorations of exciting, new physics. According to the Gurarie and Rey theory groups, ultracold dipolar molecules can do even more interesting things than swapping spins. For instance, spin swapping occurs naturally when ultracold potassium-rubidium (KRb) molecules are in two of their four possible excited and ground states. The differences in two states are sufficient to cause a spinning molecule to slow down at the same time another molecule begins to rotate.