Nd_(4)Ni_(3)O_(10)的红外光谱研究

Infrared spectroscopic study of Nd_(4)Ni_(3)O_(10)

无限层平面四方相镍氧化物薄膜以及高压下双层Ruddlesden-Popper(RP)相镍氧化物单晶中相继发现的超导电性引起了超导领域的广泛兴趣.常压下RP相镍氧化物中迄今未观测到超导电性,但双层和三层RP相镍氧化物中存在金属-金属转变.本文对三层RP相镍氧化物Nd_(4)Ni_(3)O_(10)进行了红外光谱研究,发现低频的光电导谱存在Drude响应,和材料的金属性相符.低频的光电导谱需要两个Drude分量来描述,说明材料中有多个能带穿过费米能级.在金属-金属转变温度T^(*)以下,低频的光电导谱被压制,表明费米面上有能隙打开;丢失的谱重被转移到很高的能量范围,表明电子强关联效应在金属-金属转变中起重要作用.本文的实验结果为理解RP相镍氧化物中金属-金属转变的本质提供关键信息.

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 Nd_(4)Ni_(3)O_(10) 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 Nd_(4)Ni_(3)O_(10).This work offers key information to understand the mechanism of the metal-to-metal transition in RP-phase nickel oxides.