Toward complete characterization of quantum critical dynamics in cuprate superconductors

Hsiao-Yu Huang^1*, Chung-Yu Mou^2,3, Amol Singh¹, Jia-Syuan Su¹, Jun Okamoto¹, Seiki Komiya⁴, Chien-Te Chen¹, Ting-Kuo Lee^3,5, Atsushi Fujimori^1,2,6, Di-Jing Huang^1,6,7

¹National Synchrotron Radiation Research Center, Hsinchu, Taiwan
²Center for Quantum Technology and Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
³Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
⁴Central Research Institute of Electric Power Industry, Kanagawa, Japan
⁵Institute of Physics, Academia Sinica, Taipei, Taiwan
⁶Department of Physics, University of Tokyo, Tokyo, Japan
⁷Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan

* Presenter:Hsiao-Yu Huang, email:huang.hy@nsrrc.org.tw

Superconducting cuprates exhibit novel physical properties within an intricate phase diagram. Quantum phase transitions, driven by quantum fluctuations at zero temperature, are expected to provide an underlying perspective on cuprate complexities. However, the existence of a quantum critical point (QCP) in cuprates remains controversial. Here, we present high-resolution resonant inelastic X-ray scattering measurements to unveil intriguing quantum fluctuations associated with charge density waves (CDW) that display distinct relaxation and damping characteristics in cuprate superconductor La_2-xSr_xCuO₄. As the QCP is approached, the characteristic energy of the fluctuation reduces, while the CDW relaxation rate increases. These intricate CDW dynamics illuminate the intertwining between CDW and superconductivity. Our findings introduce a new viewpoint for understanding the quantum phase transition in cuprates, shedding light on the challenges in detecting QCP.

Keywords: cuprate superconductor, quantum critical point, charge density wave