Research Breakthrough in Quantum Materials
Researchers at the Korea Advanced Institute of Science and Technology (KAIST), in collaboration with Stanford University, have successfully visualized the formation and disappearance of charge density waves (CDWs) within quantum materials. This achievement marks the first direct spatial observation of these electronic patterns.
Understanding Charge Density Waves
Charge density waves are ordered patterns formed when electrons align at regular intervals in certain quantum materials, typically at very low temperatures. Understanding these patterns is crucial for comprehending quantum phenomena such as superconductivity, where electric current flows without energy loss. Superconductivity is utilized in technologies like MRI scanners and maglev trains, and strongly correlated quantum states are foundational for next-generation quantum technologies, including quantum computers. Precise control over electrons is necessary to apply these phenomena to quantum computing.
Methodology
The research team, led by Professors Yongsoo Yang, SungBin Lee, Heejun Yang, and Yeongkwan Kim of KAIST’s Department of Physics, utilized a specialized electron microscope cooled with liquid helium and four-dimensional scanning transmission electron microscopy (4D-STEM). This enabled real-time observation of electronic pattern changes at temperatures as low as approximately –253 °C. The resolution of the electron microscope allowed for the visualization of features one hundred-thousandth the width of a human hair.
Key Findings
The study revealed several significant observations:
- Non-uniform Pattern Appearance: Electronic patterns did not appear uniformly throughout the material. Some regions exhibited clear stripe-like patterns, while adjacent areas showed no such organization, indicating a coexistence of ordered and disordered states.
- Influence of Internal Strain: The non-uniformity of these patterns was linked to subtle internal strain within the material, suggesting that minor pressures or distortions can disrupt electronic pattern formation.
- Persistent Quantum Order Islands: In certain areas, electronic patterns remained stable even as temperatures increased, indicating the existence of localized "islands" of quantum order that persist at higher temperatures. This behavior challenges existing theoretical frameworks.
- Quantitative Spatial Influence: The study also quantitatively determined the spatial extent of influence among electrons forming a charge density wave, providing a new analytical method for understanding electron order and maintenance in quantum materials.
Implications for Quantum Technology
The findings provide direct insights into the behavior of electrons in quantum materials, which was previously studied primarily through theoretical models or indirect measurements. Since charge density waves can either compete with or cooperate with superconductivity, this research has implications for high-temperature superconductors. Understanding the conditions for stable electronic patterns may lead to the development of materials where superconducting currents flow more efficiently.
Professor Yongsoo Yang stated that this work allows direct observation of subtle changes in electronic order and quantum states at ultralow temperatures, accelerating the development of materials for future quantum technologies.
Publication and Support
The research was co-authored by Seokjo Hong, Jaewhan Oh, and Jemin Park from KAIST. The results were published on January 6, 2026, in Physical Review Letters. Support for the research was provided by the National Research Foundation of Korea through various programs and the KAIST Singularity Professor Program.