Peering into a Tiny World—and Finding Surprises

Dr. Myriam Sarachik examines magnets and electrons at the quantum edges of physics.

In the grand auditorium of Paris' UNESCO House last March, five scientists from around the globe gathered to receive the L'OREAL-UNESCO for Women in Science awards of $100,000 each. There were researchers assembled from the University of Paris-Sud, the Federal University of Rio de Janeiro, the University of Tunis, and the University of Keio (in Japan) at the table of honor--and also, one from City College and The Graduate Center. That was Distinguished Professor of Physics Dr. Myriam Sarachik, decorated as North American Laureate by the awards jury for her "high level of creativity and openmindedness."

Distinction--and travel--are hardly new for Sarachik, who has served as the third-ever female president of the American Physical Society, in 2003; received the Sloan Public Service Award from the Fund for the City of New York in 2004 for "blazing trails as a scientist, researcher, teacher, mentor, and humanitarian"; been awarded the 2005 Oliver E. Buckley Prize in Condensed Matter Physics; testified before Congress about the importance of funding for scientific research; and authored some 150 professional journal articles in her career to date.

Born in Antwerp, Belgium and possessing an early love of puzzle-solving and music, Sarachik moved to Cuba as a child of 8 with her family, later immigrating to the U.S. and attending the prestigious Bronx High School of Science. She has been a faculty member at City College for four decades, continuously rising in a field where only a small percentage of physicists are women.

Talk about your work studying tiny, so-called 'nanomagnets'. Why do you work with Manganese-12?

Manganese-12 is the simplest and most studied member of an interesting class of materials called molecular magnets, or single-molecule magnets. It is an organic material that consists of molecules composed of carbon, hydrogen, oxygen and manganese. Each molecule has twelve manganese atoms locked together to form a magnet that is large by atomic standards but tiny by everyday standards. These little magnets like to point along a particular direction in the crystal, either with the north pole "up" or "down".

The size of the magnets is intermediate between the world of the small, where quantum physics dominates, and the large, where classical physics rules; the connection between these two worlds has always been fascinating to physicists. At high temperatures, the magnets have access to a lot of energy and they can flip from one orientation to the other with the greatest of ease. At low temperatures, the magnets have much less energy and they tend to get stuck in the "up" or the "down" position.

However, quantum mechanics makes it possible for them to flip over by a process called 'tunneling,' even when they don't have enough energy to do it classically. That's very interesting and potentially useful.

Why is it useful? What's the practical application of this?

There are two ways in which this could be useful: for high density storage of information, and also possibly for quantum computation, an entirely new method that has been proposed for doing computation using quantum mechanics.

Current technology stores information in the form of bits (one or zero, up or down). If we could store the ones and zeroes (magnets pointing up or down) on Mn-12 molecules, we could pack 10,000 more bits on a square than we can now.

When you deal with elements that are as small as one nanometer, you're down to dimensions where quantum mechanics dominates the behavior. That means you're no longer dealing with bits that are reliably 'one' or 'zero', but rather a combination called a "qubit" [cue-bit]. It may be possible to take advantage of this to do a completely different kind of computation which is potentially much more powerful.

Most of your work is done at very low temperatures. Why?

It is important in these molecular magnets to go down to low temperatures because the clusters of manganese atoms that form the little magnets fall apart at higher temperatures. Things also become complicated at higher temperatures because other things happen: the atoms and molecules of the crystal vibrate, for example.

Does that mean any resulting technologies will need to be kept very, very cold as they operate?

The attempt now is to try to achieve the same technologies at temperatures that are not so low. Chemists are trying to make other variants of these materials that do not require such low temperatures. There are many people doing a lot of work on this.

You have also studied resistance and conductivity of electrons at very low temperatures. What did you find?

As you decrease the temperature of a metal, the resistance to current flow goes down, while in an insulator it does the opposite. It was believed for many years that two-dimensional systems (thin layers) are always insulating at very low temperatures, that is, the resistance is expected to go up as you lower the temperature.

However, we found something completely unexpected. Contrary to all expectations, the resistance goes down in high-mobility two-dimensional layers, like in a metal. Is it possible to have a metal in two dimensions? This is now under intense discussion and scrutiny. We've also been studying the effect of a magnetic field, which provides another important piece of the puzzle. A magnetic field suppresses all this anomalous behavior and brings the material back to the insulating phase.

Why is this sort of research so important?

My research is quite basic, not aimed at applications. Although it gives me extra pleasure when I can see how what I'm doing could ultimately lead to a specific application or advance, my focus has been on understanding how nature works. It is very important that this activity be well funded and continued. It builds the knowledge base from which all the applications ultimately grow. And, indeed, the applications have already transformed the world we live in.

How do you see your role as a leading woman in science?

We need more women in physics, and in the hard sciences generally. We need to attract them to the field, to show them how interesting and rewarding it is. I think many students are frightened of physics. I don't really understand exactly why it is, but women in particular shy away from physics. It's a great field to be in, and I've had enormous fun in it.