Theoretical physicist Shoucheng Zhang, a pioneer in the study of topological states of matter, died on 1 December. He was 55. In a note to his friends and collaborators on 6 December, Zhang’s family said that the scientist died after “a battle with depression”.
Zhang, who was at Stanford University in California, was among the first physicists to realize — and predict in detailed calculations — how some materials long known to be insulators should be able to conduct electricity on their outer surface1,2,3. Such effects should arise because the quantum states of electrons can form shapes that are robust under perturbation, similar to knots on a string that can be pulled and twisted but not undone — features described by the mathematics of topology. The materials were dubbed topological insulators.
Zhang worked with Laurens Molenkamp, an experimental physicist at the University of Würzburg in Germany, and others to confirm his predictions in the lab. Zhang also received numerous prizes, and was, for several years, on many researchers’ lists of favourites for the Nobel Prize in Physics.
“He had an uncanny ability to join profound theoretical beauty with real-world materials and experiments,” says theorist Charles Kane of the University of Pennsylvania in Philadelphia, another pioneer in the field. “That, to me, is what is best about theoretical physics.”
Beyond the lab
Molenkamp and others remember Zhang as someone who would often go above and beyond his professional role to be kind to others. “I know many people who had personal problems, and he always helped them,” he says.
Zhang was born in Shanghai, China, in 1963. He left the country to study in Germany and, later, in the United States. More recently, he had also branched into finance and co-founded a venture-capital firm.
But the field of physics that he helped to found has had a veritable boom in the past decade. “In addition to his path-breaking scientific contributions,” Kane wrote in an e-mail to Nature, “I am grateful for Shoucheng’s tireless leadership, which played a key role in the rapid development of the field of topological insulators.”
Zhang also continued to develop ideas on other topological states of matter, including ‘Majorana states’, because they mimic the behaviour of elementary particles — first hypothesized by Italian physicist Ettore Majorana — that are their own antiparticles. Majorana states are considered to be promising candidates on which to base future quantum computers. In a paper published in October4, Zhang and his collaborators described a scheme to put this into practice that could be simpler than those suggested in previous proposals.
Claudia Felser, a materials scientist at the Max Planck Institute for Chemical Physics of Solids in Dresden, Germany, says that Zhang had a profound impact on her life — even acting as a matchmaker between her and her husband, who is a physicist — as well as on her career. “I would never have worked on topology without meeting him and being inspired by him,” she says. “He was a legend, this person.”