Physics Colloquium: Isaac Silvera, Harvard University
Professor Isaac Silvera, Department of Physics, Harvard University
Hydrogen is the simplest and most abundant element in the Universe. There are two pathways for creating metallic hydrogen under high pressures. Over 80 years ago Wigner and Huntington predicted that if solid molecular hydrogen was sufficiently compressed in the T=0 K limit, molecules would dissociate to form atomic metallic hydrogen. We have observed this transition at a pressure of 4.95 megabars. MH in this form has probably never existed on Earth or in the Universe; it may be a room temperature superconductor and is predicted to be metastable. If metastable it will have an important technological impact.
Hydrogen makes up ~90% of the planet Jupiter. It is believed to occur as a layer of liquid metallic hydrogen surrounding Jupiter’s core, responsible for Jupiter’s magnetic field, with molecular hydrogen as the outermost layer. Descending through the atmosphere, a phase transition from liquid molecular to liquid atomic metallic hydrogen occurs as the pressure and temperature increase. This first-order phase transition to liquid metallic hydrogen is at intermediate pressures (~1-2 megabars) and temperatures of ~1000-2000 K. We have also observed this liquid-liquid transition, known as the plasma phase transition. We shall discuss the methods used to observe these phases of hydrogen at extreme conditions of static pressure in the laboratory, extending our understanding of the phase diagram of the simplest atom in the periodic table.
Wednesday, September 13, 2017 at 4:00pm