A philosophical explorer of the quantum frontier in materials science

Gregor Jotzu, who joined EPFL last year as tenure track professor, leads EPFL's Dynamic Quantum Materials Laboratory at the School of Engineering. Raised in Germany and of Romanian descent, Jotzu's academic and research pursuits have taken him across the globe. An avid oarsman, he has rowed the waters of Boston, Oxford, Zurich, Hamburg, and now Lausanne. At EPFL, he is exploring the intricate world of quantum phenomena in the hopes of discovering completely new properties in hybrid materials that are a combination of matter and light.

Jotzu's academic journey began at the University of Oxford, followed by a prestigious fellowship at Harvard University as the Michael von Clemm Fellow. He completed his doctorate at ETH Zurich, focusing on quantum magnetism, driving-induced order, and topology using ultracold atoms in optical lattices. In Zurich, Gregor studied topological materials by creating an artificial solid made of atoms held in place by lasers in a vacuum chamber. By shaking this enlarged model of a solid, he could observe changes in the material’s properties as the topology changed.

In 2015, this significant contribution of an experimental setup to validate the topological model of Duncane Haldane – a prominent British physicist working at Princeton – was recognized with the Swiss Physical Society's Prize in General Physics. The following year, as Jotzu was delivering a talk as part of his application to a postdoctoral fellowship at the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) in Hamburg, news broke that Haldane had been awarded the Nobel Prize in Physics. This felicitous coincidence bodes well for the young researcher, as his work establishes an experimental platform to test the Haldane model – now forever inscribed in the halls of science.

At the MPSD, Jotzu studied novel states of matter created using ultrafast lasers. His investigations are driven by a fascination with the universe's complexity. "I think many physicists starting out want to find the Theory of Everything. And for me, it was a pivotal moment when I found out that you actually have to solve a many-body problem to just calculate the properties of a single proton," he explains.

This realization highlighted the significance of interrelatedness in physics for the researcher. Properties and behaviors of systems cannot be simply deduced by considering their individual components in isolation. Instead, these systems require an understanding of the complex interactions between numerous particles, hence the many-body problem. This early moment in his career steered his focus towards understanding and controlling the emergent properties in complex quantum systems.

As someone fascinated with interconnectedness and who is probing the relationship between the extremely small and the properties that emerge on a larger scale, it is not surprising that Jotzu finds it important to connect with nature in his downtime, notably through rowing. “When you’re rowing, you’re on the water and can observe the skyline. In Boston there were the skyscrapers, in Oxford it was a pleasant countryside. And in Lausanne, as the sun rises over the mountains on an early morning, rowing on the Lac Leman can be simply spectacular,” he says.

Where pure physics meets engineering

At EPFL, Gregor is again studying ways to control material properties using light-matter interactions. But rather than a model system, he is now working with real materials and using laser light to drive them into new states not found naturally. His work goes beyond simply probing materials to actively modifying them by creating hybrid light-matter states. This method enables him to observe the dynamics of these complex systems in real time, providing insights into the formation of new orders and states.

This is where theory and application find common ground for Jotzu, where the pure physicist meets the engineer. For insights gained from these experiments can lead to the development of novel materials with unique properties. For instance, understanding how materials transition between different states (like from an insulator to a conductor) can pave the way for creating advanced materials for electronics, photonics, or energy storage applications. “I’m currently looking into getting superconductivity to work at room temperature using a laser,” he states. If successful, this endeavor could no less than revolutionize materials science specifically, and technology in general.

A scientist for society

In addition to his research, Jotzu sees the role of the professor and researcher as a public one. “I also think we scientists need to participate in discussions about how to organize society, because ultimately, there are so many questions that have a certain technological or scientific component. This is actually why, before my PhD, I spent a year in the United States studying history and philosophy of science,” he says. This belief in the importance of an open dialogue among scientists, policymakers, and the public also comes with a responsibility for the scientist to be able to place his or her research in the appropriate context.

“I think every scientist should have a basic education in history and philosophy, just to be able to see things in a certain perspective. To see how people in the past reacted to conceptually very new things,” he says. He finds electromagnetism a telling example. When it was a new technology in the 19^th century, people thought they could use it communicate with the dead and solve the intractable mind/body problem. He thinks we are seeing a similar thing happening now with quantum physics.

Not surprisingly then, Jotzu is passionate about teaching and sees it as a vital part of his role at EPFL. He is looking forward to the fall semester of 2024, when he’ll teach a master’s class on quantum materials. This is where he sees the value of a university setting, compared to a research institute, where he can teach students the fundamentals, which have been known for a century, “but is also able to give a contemporary twist to it,” as he puts it.

Above all, he believes in nurturing a critical mindset among students, encouraging them to question and understand the limitations and assumptions in scientific theories. “I think as a teacher, you have a responsibility to get across an understanding of your subject, but also a certain meta-understanding,” he says. To him, it’s important to tell students: “Ok, I'm teaching you this now, but it’s only true under certain limits, under certain assumptions. Everything could be different when the timescale or regime changes, such as with the discovery of superconductivity at very low temperatures. It’s at these edges where the most interesting, unexpected things can happen.”

Gregor Jotzu's early career has already been characterized by a deep commitment to understanding the quantum world. Charting the edges between pure science and application, Jotzu will continue, in Lausanne, to push the boundaries of the known universe, driven by the insatiable curiosity of the scientist, the philosopher, and the explorer.