NSF Award
1408598
Non-Technical Abstract:<br/><br/>Ordinary phase transitions, such as the freezing or boiling of water, involve heat energy. This team will study quantum phase transitions that occur at absolute zero where there is no heat. Zero-point energy, associated with the Heisenberg uncertainty principle, plays the role of heat in these transitions. A rising paradigm in physics, quantum phase transitions may be the origin of high-temperature superconductivity and have informed the theory of black holes. Quantum phase transitions can dramatically affect the behavior of matter at surprisingly high temperatures and lead to characteristic changes in volume as the temperature or magnetic field changes. A high-precision technique, developed with National Science Foundation support, will be used to search for these characteristic changes in volume in order to identify and better understand the underlying quantum phase transition. Novel states of matter that are expected to occur near quantum phase transitions will be sought out and studied as well. Undergraduate students participate in all aspects of this work, both on-campus and during trips to visit collaborators at research universities, national laboratories, and a company that manufactures automated temperature and magnetic field testing platforms for materials characterization. Students visiting these institutions are exposed to a "big science" environment complementing the "small science" environment at Occidental College, a national liberal arts college in metropolitan Los Angeles where most of the work will be carried out.<br/><br/>Technical Abstract: <br/><br/>Theh team seeks a better understanding of the nature of matter near quantum phase transitions, especially the delicate ordered phases that can appear nearby. Our primary focus is on Yb- and U-based heavy fermion compounds exhibiting magnetic-field induced quantum criticality and related phenomena such as magnetic order, novel superconductivity, and "hidden order." Physical behavior near a quantum phase transition is dominated by quantum fluctuations associated with the zero-point energies of the adjacent states. Remarkably, these quantum fluctuations can affect physical behavior at temperatures well above absolute zero. Low temperature phase transitions and the quantum phase transitions associated with them are a major focus of condensed matter physics, a focus on which thermodynamic information is sparse. Such information is needed for a better understanding of quantum many-body problems. A rising paradigm in physics, quantum phase transitions are invoked in explanations of high temperature superconductivity and black holes. The primary experimental method is to measure thermal expansion and magnetostriction using capacitive dilatometers (all but one developed with National Science Foundation support). The team will search for characteristic changes in volume at low temperatures in order to identify and better understand the underlying quantum phase transition. This work is carried out in collaboration with scientists at research universities, national laboratories, and a company that manufactures automated temperature and magnetic field testing platforms for materials characterization. Undergraduate students visiting these institutions will be exposed to a "big science" environment complementing the "small science" environment at Occidental College, a national liberal arts college in metropolitan Los Angeles where most of the work will be carried out.
