2024 Von Hippel Award

Claudia Felser, Max Planck Institute for Chemical Physics of Solids

Topology and Chirality

Written by Vineeth Venugopal

The Von Hippel Award, the highest honor bestowed by the Materials Research Society (MRS), recognizes exceptional originality and wisdom in scientific contributions that transcend the traditional boundaries of materials science. At the 2024 MRS Fall Meeting, this prestigious accolade was awarded to Claudia Felser of the Max Planck Institute for Chemical Physics of Solids. Felser’s pioneering research on topology and chirality has not only advanced the understanding of these fundamental phenomena but also opened doors to transformative applications in materials science and beyond.

Exploring the Intersection of Topology and Chirality

In her lecture, titled “Topology and Chirality,” Felser captivated the audience by weaving together concepts from mathematics, chemistry, and condensed matter physics. At its core, her work revolves around the design, synthesis, and investigation of single crystals and films with unique physical and chemical properties.

Topology, derived from mathematics, describes properties of structures that remain unchanged under continuous deformation. Using the Gauss-Bonnet theorem, Felser illustrated how topology governs which structures can transform into one another based on their genus, a fundamental property in mathematics. Applying this principle to condensed matter physics, topology provides a framework for understanding the behavior of electron bands, leading to the discovery of topological materials.

Chirality, on the other hand, refers to the “handedness” of a structure, whether it is left- or right-handed. In chemistry, creating chiral molecules requires chiral catalysts—a concept encapsulated in the phrase "chirality in, chirality out." Felser pointed out the universality of chirality, highlighting its role in parity violation and speculating on its relevance to the origins of the universe, as described by the Dirac equation.

Topological Materials: A Revolution in Condensed Matter Physics

Felser’s work has significantly contributed to the discovery and classification of topological materials. Among the 250,000 inorganic materials screened for topological properties, around 30% exhibit topological characteristics, ranging from insulators to semimetals. These materials challenge conventional understanding, with exotic properties rooted in their electron band topology.

One particularly groundbreaking discovery involves Dirac and Weyl semimetals. These materials host chiral electrons in their bulk, and under parallel magnetic and electric fields, they exhibit the “chiral anomaly”—a phenomenon where the conservation of chiral current breaks down. Felser’s work in this area has drawn widespread attention, even earning coverage in The New York Times under the evocative title “Universe in a Crystal.”

Chiral Crystals: Bridging Physics, Chemistry, and Applications

Felser’s research extends beyond topological materials into chiral crystals, which possess inherent handedness. These materials exhibit unique optical and electronic properties, driven by their crystal structure. For instance, PdGa, a homochiral crystal, is not only a promising catalyst but also a platform for understanding chiral electrons and spin-momentum locking at the surface.

By synthesizing materials like PtAl and PdGa, Felser and her collaborators have discovered novel fermions and giant surface states, further enriching the landscape of condensed matter physics. Such advancements provide a new basis for technologies like solar panels and catalysts, demonstrating how topological and chiral materials can address real-world challenges.

Chirality and Catalysis: A Leap in Efficiency

One of Felser’s most impactful contributions lies in the application of chirality to catalysis, particularly in oxygen reduction and oxygen evolution reactions. Her team showed that topological homochiral PdGa exhibits unprecedented catalytic efficiency, achieving over 200 times the performance of conventional materials. These findings have profound implications for sustainable energy solutions, including fuel cells and water splitting technologies.

Felser also highlighted the concept of Chirality-Induced Spin Selectivity (CISS), where the electronic spin is influenced by the chirality of a material. By integrating this principle into catalytic systems, her work bridges the gap between chemistry and physics, offering a potential pathway to solve enduring puzzles such as the chiral anomaly.

A Vision for the Future

Claudia Felser’s Von Hippel Award lecture emphasized the synergy between chemistry and physics in tackling fundamental and applied challenges. Her research not only sheds light on the universal principles underlying topology and chirality but also demonstrates their transformative potential in catalysis, renewable energy, and beyond.

As Felser concluded her talk, she inspired the materials research community to continue exploring the intersections of disciplines, where the most groundbreaking discoveries often emerge. Her work serves as a testament to the spirit of the Von Hippel Award—pioneering science that transcends conventional boundaries.

The Von Hippel Award, the Materials Research Society's highest honor, recognizes those qualities most prized by materials scientists and engineers—brilliance and originality of intellect, combined with vision that transcends the boundaries of conventional scientific disciplines.