Pursuing the aesthetics in the movement of electrons
Prof. M. Zahid Hasan; An intimate profile
While studying a bismuth-containing thermoelectric material by a synchrotron facility at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), physicist M. Zahid Hasan of Princeton University noticed that something was interfering with the electrons’ behavior inside the material. He and his team also noticed that they have observed the same unusual interference more than a decade ago during a similar experiment with the same material.
At first, they saw the interference as a problem. However, around 2007 after doing more experiments and gaining some understanding of the theory related to his team’s observations, Hasan realized that this obstruction was actually a discovery: topological insulator. A groundbreaking discovery that triggered a revolution in quantum material science that continues today and could someday lead to new generations of electronics and technologies.
Trying to get a theoretical insight about the effect, Hasan struck up a conversation with some theoretical physicists, including a fellow professor, Duncan Haldane. “At that point, I was not aware of the theoretical predictions,” he says. Through their discussions about the theoretical works, it turned out some of them date back several decades. However, those theoretical works did not provide many clues in finding the effect in the materials exhibiting this phenomenon. Hasan found out the only way to tackle the problem is by combining the fields of quantum theory, particle physics, and complex mathematics. “I had to translate all of the abstract math into these experiments,” he says. “It was like translating from a foreign language.”
In 2016, Haldane and two other physicists won the Nobel Prize in Physics for their theoretical discoveries of topological phases of matter. At the time Nobel Prize announcement, Haldane said that in his first paper about such materials, he had mentioned: “this is unlikely to be anything anyone could make.” “My work sat around as an interesting toy model for a very long time—no one quite knew what to do with it.” In its supporting materials for the prize, the Nobel Committee had cited early experiments by Hasan’s team on materials exhibiting topological insulator phases.
Hassan was born and brought up in Dhaka, Bangladesh, in 1971. “As a child, I have been curious, adventurous, dreamer, and naturally driven to achieve goals.” He was a voracious reader, but his first wonder about science came about by playing with a navigation compass. “By playing with it, I became interested to learn the way it works. Something invisible pulling compass needle along a line - an invisible force at play,” he says. Trying to figure out the mystery, Hasan broke the compass into pieces. It seems the rule of the game remained the same for him today. “There was this mysterious and invariant force at play - and this same sense of mystery and search for the underlying fundamental law of nature seems to continue to drive my research today,” he says.
Growing up, Hasan was nowhere near sure about his passion for science. He was seriously interested in entirely different things like creative writing, poetry, art, and architecture with a drive towards aesthetics. “Over time, I seem to have developed an interest in more abstract arts like mathematics and physics.” However he believes, he is driven by the inner aesthetics of the interplay between physics and mathematics to describe nature. “I had a difficult time choosing between creative writing or arts and fundamental science. He even attended some art school for some time and wrote for magazines.
In college, Hasan had the chance to take the quantum mechanics lessons from Steven Weinberg, theoretical physicist Nobel Prize laureate, at the University of Texas at Austin. Through those classes, he was fascinated by the beautiful mathematics of the angular momentum of spins. “Much of what I do today is about understanding how electrons move through complex arrays of spins in novel materials using high-energy scattering techniques,” he says. However, his interest in condensed-matter quantum physics grew during his graduate at Stanford University, where he obtained his Ph.D. in 2002.
Despite his theoretical background, he went for an experimentally challenging thesis in high-temperature superconductivity and high-energy accelerator-based spectroscopy. As a fourth-year graduate student at Stanford, he led an international collaboration with researchers from some top research institutions and labs that showed the feasibility of performing a new class of high-energy scattering experiments in condensed-mater physics.
Eventually, in 2002, he joined Princeton University, where he has held the Eugene Higgins endowed professorship since 2017. Throughout his career, Hasan has been working in many top research institutions and labs. “I think a combination of traits made it possible to utilize, operate and collaborate at many top institutions. First, it comes with proposing a great new idea for projects that others get quickly excited about. Second, good work ethics and clarity of expectations from all parties. Third, high level of scientific productivity. All these factors contribute to maintain collaborations and create new opportunities in new environments,” he says.
Hasan describes himself as a curious and adventurous person and, at the same time, reflective and meditative, always searching for more profound and more significant meaning. “What are the quantum laws of nature that govern the physical property of complex materials? This sense of unraveling a mystery - that a tangible universe can be described by invisible forces and abstract rules inspired me to pursue physics.” However, when he is not drowned in physical thoughts, he directs his curiosity toward other subjects like the history of ideas and civilizations, including the history of Abrahamic faiths and cultures and their impacts on the history of the world. Besides exploring art and architecture, he is also into music, especially the Sufi genre.
He says his parents played pivotal roles in becoming the person he is now. He remembers the day his father brought home a fossilized piece of coral when he was 5 or 6 years old. “I was fascinated by the fact that such beautiful creatures grow deep under the ocean, where I have never seen.” Then he tried to learn more about deep-sea corals and creatures by reading books, but he eagerly wanted to see the ocean itself. Imaging the existence of corals under the oceans formed a sense of mystery and an aesthetic drive in him that turned into a passion for adventure.
The following year his father took him to Cox’s Bazar – a beach town by the Bay of Bengal about 200 miles south of Dhaka – on a family vacation. That was an amazing experience – Cox’s Bazar seashore is one of the longest and most beautiful ones in the world, but he was not entirely happy! “I wanted to see a bigger and more powerful ocean. So my father took my mother and me another 100 miles down the beach and rented a high-power speedboat.”
They started heading off towards the Indian Ocean. “I can still vividly recall the waves we were surfing through as we headed south,” Hasan says. Of course, they did not make it to the Indian Ocean, but “it gave me a sense of adventure and a sense that it is worth asking big questions – Is there a bigger ocean? What is beyond the ocean?”
“The event is perhaps my greatest memory with parents. This event shows how my father helped instill a sense of adventure in me and let me pursue and nurture it. That was how I learned to ask big questions and took on real adventures to answer them." Now, Hasan himself is a father and says he will be happy to support his children in whatever they choose to do later in life, but “I think we’ll definitely get them a fancy compass for their birthday.”