The 1950s– and perhaps also the 1960s– were very special times for the development of solid-state/condensed-matter physics. The University of Illinois at Urbana was at the center of these activities. In areas like NMR and superconductivity, methods were developed which would form the basis for the next half century of science and technology. Experimentalists, including Charlie and John Wheatley, worked hand in hand with theorists, including the incomparable John Bardeen. They worked cooperatively to develop ideas, often born in Urbana, but with godparents at Harvard and Moscow and Paris. A characteristic style of broad collaboration and spirited exchange developed and spread from Illinois.

One of the defining characteristics of metals is the way they are held together. Essentially, a lattice of metal ions sits in a sea of delocalised electrons and this acts as a kind of glue that binds the structure together. These “metallic bonds” are entirely different from the covalent bonds that hold molecules together. For a start, metallic bonds are a collective phenomenon that come about because of the bulk behaviour of metal ions and delocalised electrons. But what of the bond that holds together the simplest metal structure imaginable–two metal atoms forming a bridge? Today, Harsh Deep Chopra and pals at The State University of New York at Buffalo say they have characterised the nature of this bond at room temperature for the first time. That could have important implications for the way atomic scale devices are designed and built. “The directional bonds provide high configurational stability to atomic-sized metallic devices,” say Chopra and co.