Magnet-Superconductor Hybrids

The upcoming 2011 year marks a century of superconductivity discovery. This field is currently experiencing a renaissance associated with advances in nanotechnology. Among the most promising of all the new materials are Magnet-Superconductor Hybrids. These materials combine two mutually exclusive states of nature: superconductivity and magnetism. The study of such systems has two sides. The first is the fundamental question Can we integrate materials whose properties tend to be mutually exclusive such as ferromagnetic and superconducting materials? This question was posed as one of the ten grand challenges that S. Bader, the Chair of the Division of Materials Physics of the American Physical Society, discussed in an email to the members of this society. The second side is an application of fundamental studies to the design of new superconducting materials to serve the nation energy needs.

Many people are familiar with a picture of a small magnet being repelled (levitating) by a piece of a high temperature superconductor. This is the standard demonstration in our bi-annual Physics Show. In experiment a bigger magnet would simply kill superconductivity. This shows graphically that magnets and superconductors are mutually exclusive. Ten years ago I had suggested embedding an array of magnetic nanorods into a superconductor to strongly improve its superconducting properties. Though magnets and superconductors are mutually exclusive at the macroscale (and at the atomic scale too), when combined at the nanoscale, they produce a synergistic effect: a strong increase of superconducting properties. Recently my research group has demonstrated this effect experimentally. I currently plan to continue this work on the fundamentals of interaction between nanomagnets and superconductors.

Figure shows Scanning Electron Microscope Image (top view) of the array of magnetic (nickel) nanorods (bright dots) with the height 350nm and diameter 70nm embedded into the superconducting film with thickness 100nm (light grey color). Upper dark part shows nanorods array without superconducting film.

Cold Molecules

The second direction of my research is focused on cold/slow molecular beams. This is a joint project with Dudley Herschbach. The development of laser cooling techniques has revolutionized atomic physics. However, the laser cooling method effective for alkali atoms fails for molecules, thwarted because molecules have myriad vibrational and rotational energy levels. In response to this challenge, over the past decade many innovative efforts to slow and cool molecules have been pursued. This has proved difficult, and as yet no method has emerged comparable to laser cooling in efficacy. Yet experimental advances, although thus far modest in scope, have encouraged a burgeoning variety of anticipatory theory. During the past year four book length collections of papers treating cold and ultracold molecules have appeared. Over the past three years, our team has set up a molecular beam laboratory at TAMU Physics Department. We have recently demonstrated beams of various molecules and atoms with a speed as low as 40 m/s with temperature as low as 0.5K. This is the only installation in the world, which can, in principle, decelerate any molecule/atom available as a gas. First we plan to focus on ultracold chemical reactions in cooperation with Herschbach. However, this installation can have numerous applications in different fields of physics and technology starting from quantum computing with cold dipolar molecules to slow beams of He or H atoms for use instead of very cold neutron beams, to a microscope with atomic beams with nanometer wavelengths and many other applications.

In his book Imagined Worlds, Freeman Dyson emphasizes that new directions in science are launched by new tools much more often than by new concepts. He says: The effect of a concept-driven revolution is to explain old things in new ways. The effect of a tool-driven revolution is to discover new things that have to be explained. I would add that often old concepts and new tools, when combined, enable major advances.
The slow molecule field, still fledgling, is awaiting new tools. I am captivated by the opportunity to develop such tools and to apply them to different problems in physics and chemistry. This work will be shaped by the capabilities our team will be able to develop. I feel sure, however, that this tool can also be used by other researchers.

Figure shows rotor (gold color) mounted on the top of the motor(black with white rectangular) with the gas feeding system mounted on the top of the rotor in the vacuum chamber.