Phase Transitions at BU, Looking at Stuff in a Whole New Way

in MSE Division Head's Blog
January 5th, 2012

BISHOP-172Traditionally the study of condensed matter physics focused on the nature of the ordered phases. This means the study of solids and liquids, their structures and properties. Some of the most impactful work leveraged the periodic nature of crystalline solids to gain an understanding of metals and semiconductors. The computer and the internet are the direct result of that work.

However, as research in condensed matter physics matured, the focus shifted from how these systems behaved and their properties to much more subtle questions beyond what they do to questions of why they exist at all. This is sort of like the difference between studying medicine and evolution. One field studies “how” the other studies “why”.

If you look at all the stuff in the universe, one way to think about it all is how disordered it is. Think about water for a minute. You can have crystalline solid phases, a liquid or a gas. These different phases all have very different properties and a unifying way to think about them is elusive but one useful approach is to think about disorder.

The crystalline solids are well-ordered (the molecules are all lined up like good soldiers on a parade ground), the liquid less well-ordered (commuters in Penn Station in NYC at rush hour) and the gas even less so (kindergartners at recess). As you raise the temperature you increasingly “disorder” the material as the thermally induced vibrations tear things apart. One of the surprising and interesting things about all the stuff in the universe is that many of the transitions between these various phases are abrupt, not gradual. These abrupt transitions are called “phase transitions” (the transitions between the various phases) and they can be quite sharp.

A different and important way to study condensed matter physics is to focus on how and why a system evolves from one phase to another one that might be more or less well-ordered. This is sort of like studying how one species evolves from another one less well-suited for survival. The differences tell you a lot about what is important and why.

Boston University has one of the real pioneers in this field, Gene Stanley. His seminal work on the “why” of condensed matter phases has helped to provide an intellectual framework that lets us understand the stuff in the universe in a whole new way. Interestingly, he has also taken those concepts first developed to understand condensed matter and shown that things like economies and heart attacks can also be understood within this framework. As an old guy with a lot of miles on my ticker, this last bit is of particular interest to me…..

Samuel Johnson famously said that when you are tired of London, you are tired of life. As I am discovering, the same could be said of Boston University.

Dave B.