Pioneer in spintronics celebrates birthday

What might be Harvard’s oddest birthday party unfolded last over Feb. 29 and March 1. In a lecture hall at Maxwell Dworkin, 50 physicists gathered to share the latest research in spintronics, an emerging branch of their science concerned with the quantum spin states of electrons, and to honor one-time Soviet scientist Emmanuel I. Rashba who turned 80 last October.

Rashba, a research associate in his fourth year at Harvard, helped pave the way for spintronics with his Cold War theoretical work in condensed matter physics. The field might someday displace conventional electronics, experts say, and inspire technologies that among other things compress massive amounts of data for computer memory.

Electrons — the tiny particles within atoms — have charge (negative), they have mass, and they move. But electrons also have “spin,” analogous to the way the Earth rotates on its axis.

Controlling electrons — and the “magnetic moment” their spin produces — offers the prospect of breaking away from the transistor, a 1948 invention that is still the main element of computers. (In transistors, only an electron’s charge is used, not its spin.)

Rashba is engaging, lively, and thin, though he uses a cane or walker to get around now. While his birthday occurred five months ago — the gap between event and celebration that didn’t seem to faze anyone in attendance.

Physics practitioners at the symposium honoring Rashba came from all corners of the United States and the globe, including Japan, Russia, Denmark, and Germany. “Nobody said ‘no,’” said organizer Charles Marcus. He’s a Harvard professor of physics and director of the Center for Nanoscale Systems — co-sponsor of the meeting along with the Harvard School of Engineering and Applied Sciences. (Additional funding was provided by the Office of Naval Research and the Defense Advanced Research Projects Agency.) 

There were 12 lectures and a Friday afternoon display of research called a poster session. The lectures investigated issues such as spin-orbit coupling, spin coherence in semiconductors, graphene bilayers, and optical control of spin in quantum dots.

Along with Rashba, quantum dots were the stars of the conference. As small as 100 nanometers — billionths of a meter — across, quantum dots are artificial atoms whose size and shape can be changed by applying an electrical field. These tiny semiconductor devices may someday speed up, miniaturize, and otherwise improve transistors, lasers, and medical imaging.

“It’s in the spirit of collegiality, more than honor, that we meet today,” said Marcus, opening the conference. “Be as open and as loud and as disrespectful of authority as we are in the Journal Club Emmanuel [attends] every Thursday.”

Thursday is the on-campus day for Rashba, who lives in Newton with his wife Erna, a Soviet-trained architect. He sits in on two seminars: a condensed matter theory group, and the spirited Journal Club, which is devoted to facets of spintronics being pursued by several research groups at Harvard.

Despite the deeply technical nature of the two-day conference, it started on a nearly sentimental note. Standing just a few feet in front of his old friend Rashba, German physicist Gottfried Landwehr of the University of Würtzburg — a world expert in high magnetic fields — recalled a scientific relationship that began when the Iron Curtain was still in place. (The two co-edited two volumes reviewing East-West advances in condensed matter physics.)

“You have a worldwide reputation now,” said Landwehr, wishing Rashba years more of health and work. He made note of his friend’s breakthrough 1960 paper, whose main concept is now memorialized as the “Rashba effect.” (The idea: In semiconductors, the effect of electrical field on electron spin may be orders of magnitude more efficient than that of magnetic field.)

Landwehr also alluded to a lesser-known paper, “Looking Back,” an autobiographical essay Rashba wrote in 2003 for the Journal of Superconductivity.

The essay had drama: Two weeks after the Nazis invaded the Soviet Union, the 13-year-old Rashba and his family fled eastward from Kyiv, Ukraine. Two months later, all the Jews who had stayed in Kyiv were murdered.

The essay acknowledged luck too. Luck that made that escape possible, and luck that Rashba was born in 1927, the cut-off year for wartime conscription into the Soviet army. Boys only a couple of years older, he wrote, “got a long break in their education, and only a few of them came back.” (During World War II, the Soviet Union lost about one-sixth of its population — and the fraction was much larger for young men.)

Landwehr told his old friend, “You had a very strong will to survive.”

In Rashba’s career, that also meant surviving a Soviet scientific bureaucracy — “a scientific Khmer Rouge,” he wrote — that failed to promote the gifted, smothered progress with secrecy and political intrigue, blocked international dialogue, and restricted advancement for Jews.

Being from a Jewish family was a racial mark that followed Rashba like a shadow after graduation from Kyiv University, despite his excellent grades. That accident of birth delayed Rashba’s graduate work by five years, and slowed his professional progress even after a Ph.D.

Rashba was 40, and living in Moscow — seven years after his breakthrough paper — before he was finally allowed to teach physics at a university. And until 1991, when Rashba and his wife emigrated to the United States, he could travel abroad only rarely.

Starting academic life anew at age 64, Rashba spent six months at City College of New York, taught at the University of Utah, and worked for the State University of New York at Buffalo before moving to Harvard.

In closing remarks at the conference, Rashba seemed to want to put things back in order — away from his personal story. “Our main business here is physics,” he told the assembled scientists — and in spintronics, advances are coming very fast.

In 2001, experiments were on a macroscopic scale, said Rashba. Today they are “nanoscopic,” he said, involving studies of single electrons spinning in a semiconductor environment.

“Further progress requires new physical ideas,” said Rashba, including new materials. He called the future of spintronics “promising.”

At the end of two days, did Rashba himself learn anything? “Of course,” he said, leaning on a cane near his Lyman Hall office. “It’s a way of catching up. Nobody can do everything. The brain won’t allow it.”