High-energy spin dynamics of the high-Tc nickelate superconductor La3Ni2O7

The mechanism of high-Tc superconductivity has been a long-standing question for several decades. In cuprate and iron-based superconductors, spin fluctuations have been widely believed to be important for the superconductivity. Recently, our group reported the superconductivity in the bilayer nickelate La3Ni2O7 with a maximum Tc of 80 K under pressure. So far, key spectroscopic results about the spin dynamics are absent to clarify if spin fluctuations are also important for the high-Tc superconductivity in La3Ni2O7. In last cycle, we have successfully performed an INS experiment on a powder sample of La3Ni2O7 at MERLIN to get INS results below 160 meV. However, no observable spin-excitation signal can be seen. A possible reason for the absence of spin fluctuation in La3Ni2O7 could be the formation of dimer singlet due to the bilayer structure. Based on the theoretical predictions, the intradimer interaction Jc can be as high as 180 meV, which means that there could be spin excitations from dimers in higher-energy region (beyond the coverage of the Ei = 160 meV at MERLIN). To clarify if there are dimer-induced spin excitations above 160 meV, we propose to perform high-energy INS measurements with higher Ei = 400 meV at MAPS on the same La3Ni2O7 sample. The coming results and our previous results from MERLIN experiment will provide a clear and complete picture on the spin dynamics of La3Ni2O7, which is crucial to understand its high-Tc superconductivity.