NTHU Researchers Identify Quantum Critical Point in Cuprate Superconductors

Insider Brief

• Researchers from National Tsing Hua University (NTHU) and international partner institutions have identified definitive evidence of a quantum critical point in high-temperature cuprate superconductors.
• Using resonant inelastic X-ray scattering (RIXS), the team observed quantum critical scaling in lanthanum strontium copper oxide (LSCO), providing evidence for the previously obscured critical point.
• The findings distinguish two electronic regimes, with charge density waves, superconductivity and pair density waves coexisting on one side of the critical point, while a superconducting state exists beyond it.

PRESS RELEASE — Nearly 40 years after the discovery of cuprate high-temperature superconductors, the key mechanism behind their superconductivity at relatively high temperatures remains one of the most important unsolved problems in physics. An international research team including Chung-Yu Mou, Dean of the College of Science at National Tsing Hua University (NTHU) in Taiwan, has provided the first definitive evidence of a quantum critical point (QCP) in the complicated phase diagram of high-temperature cuprate superconductors—a point long obscured by the superconducting state. The team also clarified how the material’s quantum states change on either side of this critical point.