RUI: Quantum Criticality in Rare-Earth and Actinide-Based Intermetallics

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****NON-TECHNICAL ABSTRACT****Classical phase transitions, such as the freezing or boiling of water, involve heat energy. This individual investigator award will support a study of quantum phase transitions which 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. 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 a magnetic field changes. A high-precision technique, developed with NSF support, will be used to search for these characteristic changes in volume in order to identify and characterize the underlying quantum phase transition. Novel states of matter that may occur near quantum phase transitions will be sought out and studied. Undergraduate students will participate in all aspects of this work, both on-campus and during trips to national laboratories and other collaborating institutions. ****TECHNICAL ABSTRACT****This individual investigator award will support a study of quantum criticality in several rare-earth and actinide-based intermetallic compounds. The thermal expansion and magnetostriction of these materials will be measured using a capacitive dilatometer developed with NSF support. Phase diagrams will be mapped out and phase transitions between the low temperature states of these materials will be thermodynamically characterized. These dilation measurements will be combined with existing specific heat measurements in a Gruneisen analysis to determine the volume dependence of the characteristic energies of these fascinating materials. Specific signatures of quantum criticality will be sought, such as a sign change of the thermal expansion and divergence of the Gruneisen parameter as the temperature approaches absolute zero. Novel states of matter that may occur near quantum phase transitions will be sought out and studied. Undergraduate students will participate in all aspects of this work, both on-campus and during trips to national laboratories and other collaborating institutions.