For decades, it has been widely believed that electrons move most efficiently in materials that are clean and highly ordered. Much like water flowing more easily through a smooth pipe, conventional wisdom has held that electrical transport improves as a material's internal structure becomes more perfectly arranged.
However, a recent study shows that the opposite can also be true. A research team at POSTECH in South Korea has discovered that engineered disorder can actually enhance electron transport.
The work was conducted by Prof. Hyungyu Jin of the Department of Mechanical Engineering at POSTECH (Pohang University of Science and Technology), Dr. Sang Jun Park (currently a postdoctoral researcher at the National Institute for Materials Science (NIMS), Japan), Prof. Hyun-Woo Lee of the Department of Physics at POSTECH, and Ph.D. student Hojun Lee. Their findings were recently published in Physical Review Letters, a leading journal in physics published by the American Physical Society.
The researchers investigated a phenomenon known as transverse electron transport, in which an electrical voltage emerges perpendicular to the direction of the applied current or temperature gradient. Such effects occur in magnetic materials and are actively studied because they can be used in technologies such as magnetic sensors, next-generation electronic devices, and thermoelectric systems that convert heat into electricity.
Until now, achieving strong transverse transport was generally thought to require exotic quantum materials or extremely high-quality single crystals with very few defects. In other words, the prevailing view was that materials needed to be as structurally ordered as possible.
Instead of trying to eliminate disorder, the research team took a different approach. They physically combined two magnetic materials while preserving the distinct properties of each component. The resulting composite contained coexisting amorphous (disordered) and crystalline regions.
Surprisingly, the transverse electron transport in this mixed structure became significantly stronger than in either material alone. Both experiments and theoretical calculations confirmed the enhancement.
The key lies in how electrons move through the composite material. Rather than traveling in straight paths, electrons follow complex trajectories as they pass through regions with different structural and electronic properties. As their motion repeatedly bends while navigating these regions, the sideways component of their movement becomes amplified, leading to stronger transverse transport.
The findings challenge a long-standing assumption in materials science that the properties of composite materials simply reflect the average of their constituent components. Instead, the study demonstrates that the way different materials are structurally integrated can itself generate entirely new physical effects.
The researchers also showed that the phenomenon does not rely on rare or expensive quantum materials. Experiments using iron-based magnetic systems produced transverse transport performance comparable to that of some high-quality quantum materials, suggesting a new pathway for designing high-performance electronic materials using relatively accessible compounds.
"This work opens a pathway toward designing high-performance materials without relying on rare quantum materials," said Prof. Hyungyu Jin, the corresponding author of the study. "The concept could lead to new opportunities in spintronics and thermoelectric energy-conversion technologies."
Co-corresponding author Prof. Hyun-Woo Lee added, "Our results suggest a new perspective in which disorder is not merely a defect to avoid, but a structural element that can be deliberately used in materials design."
The research was supported by the Samsung Future Technology Development Program, the National Research Foundation of Korea, and the Ministry of Science and ICT. The experimental samples were provided by Proterial Korea.
