Theoretical analysis on the possibility of superconductivity in the trilayer Ruddlesden-Popper nickelate La4Ni3O10 under pressure and its experimental examination: Comparison with La3Ni2O7

Abstract

We study the possibility of superconductivity in a trilayer Ruddlesden-Popper nickelate La4Ni3O10 under pressure both theoretically and experimentally, making comparison with the recently discovered high Tc superconductor La3Ni2O7, a bilayer nickelate. Through DFT calculations, we find that a structural phase transition from monoclinic to tetragonal takes place around 10–15 GPa. Using the tetragonal crystal structure, we theoretically investigate the possibility of superconductivity, where a combination of fluctuation exchange approximation and linearized Eliashberg equation is applied to a six-orbital model constructed from first-principles band calculations. The obtained results suggests that La4Ni3O10 may also become superconducting under high pressure with Tc comparable to some cuprates, although it is not as high as La3Ni2O7. We also perform experimental studies using our polycrystalline samples of La3Ni2O7.01 and La4Ni3O9.99. The superconducting transition of La3Ni2O7.01, with a maximum onset Tc of 67.0 K at a pressure of 26.5 GPa, is confirmed by a drop in the electrical resistance as well as the magnetic-field dependence of the resistance. Quite interestingly, similar temperature and magnetic field dependencies of the resistance are also observed for La4Ni3O9.99, where a drop in the resistance is observed at lower temperatures compared to La3Ni2O7.01, under pressures of 32.8 GPa and above. Given the theoretical expectation, the reduction in the resistance can most likely be attributed to the occurrence of superconductivity in La4Ni3O9.99. The temperature at which the resistance deviates from linear behavior, considered as the onset Tc, monotonically increases up to 23 K at 79.2 GPa, which is opposite to the pressure dependence of Tc in La3Ni2O7.01.

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