Lithium Under High Pressure

Dr. Shanti Deemyad
Department of Physics and Astronomy
University of Utah

At low temperature, large lattice zero point energy of light materials dominates the lattice kinetics leading to unusual effects such as superfluidity in helium isotopes. The physics of ultra light systems, especially at low temperatures, is not sufficiently explained by the static lattice models. It has been argued that lattice quantum contributions become enhanced under compression in systems with long range interactions such as Coulomb interactions. Lithium is the lightest metallic solid at ambient pressure and remains metallic up to 68 GPa. At ambient pressure, lithium is the prototype of a simple metal, with a nearly spherical Fermi surface. The structural and electronic properties of lithium at high densities, however, are highly counterintuitive and lithium undergoes series of symmetry breaking structural phase transition and a exhibits pressure induced superconductivity. In addition, because of its low atomic mass, lithium may behave as a quantum solid. If this is the case, the physics of lithium at high densities would resemble that of metallic hydrogen, and is of critical interest. Studies on properties of lithium under high pressure has been challenging due to its strong reactivity. In this talk I will review the unusual physics of lithium at extreme pressures and present our recent experimental results on P-T phase diagram of lithium.