cuprate high-temperature superconductor, quantum critical point, resonant inelastic X-ray scattering, Taiwan Photon Source, synchrotron radiation
First Observation of a Hidden Quantum Critical Point in Cuprate High-Temperature Superconductors by NSRRC TPS 41A Research Team Led by Dr. Di-Jing Huang
2026/08/17
Since their discovery, high-temperature superconductors have remained a major research focus in condensed matter physics, with their underlying mechanisms continuing to intrigue scientists for decades. An international research team led by NSRRC Distinguished Scientist Di-Jing Huang, as well as Chair Professor Chung-Yu Mou, Honorary Chair Professor Atsushi Fujimori, and Academician Ting-Kuo Lee from National Tsing Hua University has, for the first time, confirmed the existence of a quantum critical point in the phase diagram of cuprate high-temperature superconductors, which has been a long-sought feature that had remained undiscovered for more than 30 years. The research findings have been published in the prestigious journal Nature Communications.
Using high-resolution resonant inelastic X-ray scattering (RIXS) measurements at TPS 41A of Taiwan Photon Source at NSRRC, the research team identified a quantum critical point hidden beneath the d-wave superconducting phase in the cuprate high-temperature superconducting phase diagram. The study reveals that this quantum critical point arises from the interplay between charge density waves and superconducting pairing density waves, belonging to a universality class with O(4) symmetry. This breakthrough provides a new understanding of the complex physical behaviors of high-temperature superconductors, including the long-standing “strange metal” phenomenon, and represents a significant step toward unraveling the mysteries of high-temperature superconductivity. It also highlights the key role of synchrotron radiation in advancing frontier research in physics.
