Physicist Suchitra Sebastian speaks with OZY after a monthlong journey along the Silk Route. At one point, she found herself stranded at the Uzbekistan-Kyrgyzstan border, denied entry into Kyrgyzstan. Undeterred, she traveled through the night, attempting to re-enter Kyrgyzstan through Russia and was stopped periodically by rifle-armed guards.
Even in her research, Sebastian feels drawn to what she calls the “spaces betwixt.” At the University of Cambridge, she seeks to discover the bizarre properties that emerge when materials enter an in-between state as they start to shift from one phase of matter to another. These properties include superconductivity — the ability to conduct electricity without resistance or energy loss. Physicists have typically made superconductors by cooling certain materials to near-absolute zero — about -460°F, the point at which molecules and atoms show minimal movement, and a factor limiting their application in the real world. But Sebastian’s explorations of in-between states of matter may one day lead to materials that superconduct at higher temperatures.
This adventurer scientist worries that physics has become less about exploration and more about avoiding mistakes.
“If you can find [a material] that superconducts at room temperature, then you can change the world,” says Peter Abbamonte, a physicist at the University of Illinois. Superconducting cables, for instance, could transmit electricity without losing energy, unlike conventional cables, which lose up to 30 percent of the energy carried over long distances. They could also broaden the use of renewable energy, delivering electricity generated by wind and solar power plants — often concentrated in remote deserts and offshore regions — to dense cities.
In 2015, Sebastian made the renowned — and controversial — discovery that a material known as samarium hexaboride acts like both an insulator, which doesn’t conduct electricity, and a metal, which does. If reproduced and validated by other research groups, “that would really be a landmark for the field,” says Abbamonte. Ruslan Prozorov, a condensed matter physicist at Iowa State University and DOE Ames National Laboratory, adds that Sebastian “doesn’t shy away from making statements she thinks are correct, even if they go against common theories.”
It’s out-of-the-box thinking that’s essential for scientific progress, but Prozorov cautions that more research is needed to confirm Sebastian’s claims. What’s more, Abbamonte says, “most of the projected uses are maybe not even a few years, but quite some years away.”
Sebastian, 41, has large, wide-set eyes and speaks with breathless enthusiasm. Raised by her mother, she spent a peripatetic youth in India, the U.K. and Berkeley, California. She loved studying physics at the Women’s Christian College in Chennai but found academia “very insular” and switched gears. After earning an MBA, she worked in management consulting, which lacked the possibility of discovery she craved. She returned to physics, enrolling in a doctoral program at Stanford.
And that’s when she saw a material she was researching behave differently at extremely low temperatures from what she had predicted. “It looked like we were measuring a three-dimensional piece of crystal,” Sebastian says, “but the spins [of the elementary particles comprising it] were behaving like they would in a two-dimensional material” — that is, the spins were arranged in layers, and only those in the same layer aligned with each other. “It was my first exposure to making a discovery,” she recalls. “It didn’t seem like work anymore. It was play.”
Sebastian continues to adjust the parameters of materials — exposing them to high pressure and strong magnetic fields — thereby nudging them toward the liminal state between different phases of matter, known as the quantum critical point. Think of the point when water turns into steam: The quantum critical point is similar, except it’s dominated by strange quantum behavior, such as the fleeting appearance of particles out of nothing. The phases of matter on either side of this point are so unstable they create the opportunity for a new, more stable phase to emerge — one featuring exotic properties — like superconductivity.
In this way, rather than rely on serendipity, Sebastian seeks to systematically identify the ingredients needed for superconductivity at higher temperatures and find materials that naturally possess them. And if they turn out to be not quite superconducting? She could “fine-tune” them by adjusting the magnetic field or pressure to trigger superconductivity. Ultimately, she hopes to use this “quantum alchemy” to make superconductors from a variety of materials, cull the most promising candidates and use them to guide the production of optimal superconductors.
Copper oxide superconductors may offer a starting point. They’re the best-studied materials that superconduct far above near-absolute zero. Earlier studies suggest their high-temperature superconductivity may be connected to a mysterious in-between state, in which they show properties of both metals and nonmetals. The state of matter Sebastian discovered in samarium hexaboride could shed light on the origins of high-temperature superconductivity in copper oxide superconductors, which could, in turn, suggest how to fine-tune other materials so they too could superconduct at higher temperatures, possibly even at room temperature.
Sebastian’s group has found that 2D materials, and those on the cusp of being magnetic, also seem to have the necessary ingredients for high-temperature superconductivity. They’ve shown that pinching a magnet with a diamond anvil at extremely high pressures turns the magnet into a superconductor, a method they’ve used with other materials they suspect to be close to superconducting.
While it’s unclear whether Sebastian’s research will lead to room-temperature superconductors, she doesn’t let doubt consume her. “If it stops being fun, I’ll find the next thing to do,” she says. This adventurer scientist worries that physics has become less about exploration and more about avoiding mistakes. “If the goal is never to make a mistake, you’re never going to make a discovery.” The quest for energy efficiency may be well worth the wrong turns along the way.
