Phases of Matter: Remarkable Changes of Properties By Varying Temperature and Pressure

Isaac Silvera (Department of Physics)
First-Year Seminar 52Y  4 credits (fall term)   Enrollment:  Limited to 12

A gas of atoms or molecules will usually condense into a liquid phase, followed by a solid phase as temperature is lowered. Consider water: vapor, liquid, solid! The solid phase will generally have a crystalline structure (liquid is amorphous or has no long-range order).  It can be an insulator, semiconductor, or metal; it can be magnetic or non-magnetic. In this seminar we shall discuss a number of remarkable phases of matter. Below a certain temperature a metal can become superconducting, flow of electrical current without resistance; helium liquifies and at lower temperature becomes a superfluid, fluid flow without dissipation. As temperature is lowered, magnetic moments on atoms in a solid align and one observes a ferromagnetic or antiferromagnetic phase. Not all materials have a solid phase: helium remains a liquid as temperature approaches absolute zero. But, applying pressure causes liquid helium to solidify.  We shall discuss not only the materials but the techniques to create high and low temperature, high pressure, and high magnetic fields that affect the phases of matter and how they are studied. We will not carry out rigorous arguments for the behavior of matter, but rather rely on so-called “hand-waving” arguments.