Infrared spectroscopic study of Nd4Ni3O10

This is the authors' abstract. We don't add key points for this paper.

The discovery of superconductivity in infinite-layer planar square phase nickel oxide thin films and bilayer Ruddlesden-Popper (RP)-phase nickel oxide single crystals under high pressure has garnered extensive interest in the superconductivity field. Superconductivity has not yet been observed in RP-phase nickel oxides at ambient pressure, but a metal-to-metal transition in the bilayer and trilayer RP-phase nickel oxides is observed. In this work, the optical properties of the trilayer RP-phase nickel oxide Nd4Ni3O10 are studied. Low-frequency optical conductivity shows a Drude response, which is consistent with the metallic nature of the material. Two Drude components are needed to describe the low-frequency optical response, demonstrating the presence of multiple electronic bands crossing the Fermi level. Below the metal-to-metal transition temperature T*, low-frequency optical conductivity is suppressed, suggesting the opening of an energy gap on the Fermi surface; the lost spectral weight is transferred to a very high energy range, hinting that the strong electronic correlation effect plays a significant role in the metal-to-metal transition in Nd4Ni3O10. This work offers key information to understand the mechanism of the metal-to-metal transition in RP-phase nickel oxides.