Quantum fluctuations of charge order induce phonon softening in a superconducting cuprate
Hsiao-Yu Huang1*, A. Singh1, C. Y. Mou2,3, S. Johnston4, A. F. Kemper5, J. van den Brink6, P. J. Chen7,8, T. K. Lee9,10, J. Okamoto1, Y. Y. Chu1, J. H. Li3,1, S. Komiya11, A. C. Komarek12, A. Fujimori13,1, C. T. Chen1, D. J. Huang1
1National Synchrotron Radiation Research Center, Hsinchu, Taiwan
2Center for Quantum Technology, National Tsing Hua University, Hsinchu, Taiwan
3Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
4Department of Physics and Astronomy, The University of Tennessee, Knoxville, USA
5Department of Physics, North Carolina State University, Raleigh, USA
6Institute for Theoretical Solid State Physics, IFW Dresden, Dresden, Germany
7Department of Mechanical Engineering, City University of Hong Kong, Hong Kong, China
8Hong Kong Institute for Advanced Study, City University of Hong Kong, Hong Kong, China
9Institute of Physics, Academia Sinica, Taipei, Taiwan
10Department of Physics,, National Sun Yat-sen University, Kaohsiung, Taiwan
11Central Research Institute of Electric Power Industry, Kanagawa, Japan
12Max Planck Institute for Chemical Physics of Solids, Dresden, Germany
13Department of Applied Physics, Waseda University, Tokyo, Japan
* Presenter:Hsiao-Yu Huang, email:huang.hy@nsrrc.org.tw
Quantum phase transitions play an important role in shaping the phase diagram of high-temperature cuprate superconductors. These cuprates possess intertwined orders which interact strongly with superconductivity. However, the evidence for the quantum critical point associated with the charge order in the superconducting phase remains elusive. Here we show the short-range charge orders and the spectral signature of the quantum fluctuations in La2-xSrxCuO4 (LSCO) near the optimal doping using high-resolution resonant inelastic X-ray scattering. On performing calculations through a diagrammatic framework, we discovered that the charge correlations significantly soften several branches of phonons. These results elucidate the role of charge order in the LSCO compound, providing evidence for quantum critical scaling and discommensurations associated with charge order.

Keywords: Charge density waves, Superconductivity, Phonons, Resonant inelastic X-ray scattering