Research Fellows Directory
Dr Christian Ruegg
University College London
Phase transitions are familiar from our everyday experience, such as water molecules forming a gas, liquid, or solid depending on temperature and pressure. Physicists are interested in finding model systems to understand similar transitions that do not involve changes in the form of the material being studied, but its internal properties. In a solid material containing copper atoms, for example, each atom has a magnetic moment associated with it, which can be thought of acting like it was a tiny magnet (spin). These magnets can exist in different arrangements (or, phases) that can be controlled by parameters like the interactions between moments, temperature, and magnetic field. Dr Christian Ruegg, a University Research Fellow at the London Centre for Nanotechnology, recently managed to explore and control such phases at the most fundamental atomic level; in particular, he looked at pairs of magnetic moments in so-called quantum magnets, at temperatures close to absolute zero. The quantum state of the pairs can be tuned and closely monitored by different experimental techniques, giving the unique opportunity to study exciting exotic properties of matter. In the words of Dr Ruegg, “For many years the arrangement of magnetic atoms on a ladder-like structure has been the prototypical system for theoretical studies in quantum magnetism, but suitable model materials were lacking, in particular for experiments in a magnetic fields. Well, I love it when, finally, a plan comes together”.
The results of these pioneering studies contribute directly to our fundamental understanding of the states of matter and interactions between magnetic moments. But Dr Ruegg also points out that the basic principles discovered now have also direct implications for future applications of magnetism in technology like the miniaturisation of storage devices and even maybe quantum computers.