Infrared spectroscopic study of Nd4Ni3O10

The discovery of superconductivity in infinite -layer planar square phase nickel oxide thin films and bilayer RuddlesdenPopper (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.