Graduate student comes up big twice with research

Shanti Deemyad hit the jackpot. Not once, but twice.

Deemyad, a fifth-year graduate student in physics in Arts & Sciences, recently concluded groundbreaking research on the superconductivity of lithium.

And her study was a recent cover story of Physical Review Letters, the pre-eminent physics journal in the world for publishing important results in the field, with her as first author.

To publish in this journal at all is difficult, as the acceptance rate is very low. And for a graduate student to be the first author of a groundbreaking study is even rarer.

Superconductors are materials with infinite electrical conductivity and perfect diamagnetism — meaning that contrary to regular conductors, there are no energy losses when the electrical power is carried through a superconductor.

Four years ago, lithium was predicted to become a superconductor under pressure. But due to difficult experimental conditions of working with lithium, the discovery of the superconductivity in lithium didn’t happen until 2002.

But that first discovery was somewhat flawed.

“Two groups reported the observation of superconductivity in lithium before us,” said Deemyad, who is doing her doctoral research with James S. Schilling, Ph.D., professor of physics. “Neither of these groups used any pressure medium, which means that their samples were squashed under non-uniform pressure conditions.

“Since the distribution of pressure in the material under these highly non-hydrostatic conditions is not known, it is difficult to analyze the results of these experiments.”

So Deemyad and Schilling drew up their own experiments, using liquid helium as a pressure medium and performed the first experiments on lithium under the most hydrostatic conditions possible. Basically, she applied pressures as high as 670,000 atmospheres to the helium, which in turn pressed on the lithium sample equally on all sides.

This procedure was in direct contrast to the first two groups’ experiments, in which a lithium sample “was brutally squashed between two ultra-hard diamonds to 200,000 atmospheres. In such primitive experiments, the sample is squashed flat, creating a multitude of defects,” according to Schilling.

“Our phase diagram (the pressure dependence of the superconducting transition temperature) is well reproducible and differs markedly from that of the non-hydrostatic studies,” Deemyad said. “We also studied the effect of magnetic field on the superconducting transition temperature of lithium in low field regime and under different pressures.

“Our study provides the first reliable information about the superconducting phase diagram of lithium.”

The research could have important repercussions for those interested in understanding more about the core elements of the universe.

“Understanding the mechanism of superconductivity in lithium could be used to find other good candidates that may show superconductivity at higher temperatures — for example, metallic hydrogen,” Deemyad said. “These kinds of studies help us expand our horizons in basic science and may lead to very important technological advances in the future.”

To be published as first author in Physical Review Letters is almost a logical progression for Deemyad, who has attended and presented her work at six conferences and has had four papers published, three of which she is first author.

“The fact that my work on lithium was approved from the critical point of view of Physical Review Letters referees was a good measure of what is necessary for doing an attractive and high-quality scientific work,” said Deemyad, whose husband, Saveez Saffarian, is a research instructor in biochemistry and molecular biophysics in the School of Medicine. “Having our work published in a highly esteemed journal like PRL will provide us with an opportunity to attract the attention of other groups to our work.”

Her research has immediate ramifications from a personal standpoint, too.

“Having a publication in a good journal, and especially as a first author, in the short term can have a positive impact on other people’s judgment of my ability to do high quality scientific work,” she said. “However, I should and do view this only as a starting point in my scientific career.

“For a successful scientific career, many good contributions are required. And I hope to reach that point some day in the future.”

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