Study on the metal-insulator transition of Ti oxide single crystals caused from the band filling by means of photoemission and inverse-photoemission spectroscopies

利用光电发射光谱和反光电发射光谱研究Ti氧化物单晶因带填充引起的金属-绝缘体转变

• 批准号: 15540313
• 负责人: SATO Hitoshi
• 金额: $ 1.6万
• 依托单位: HIROSHIMA UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2004
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15540313/
• 关键词: Y_<1-x>Ca_xTiO_3; Metal-Insulator Transition; Electron Correlation; Hubbard Band; Photoemission Spectroscopy; Inverse-Photoemission Spectroscopy; 金属・絶縁体転移; Y1_<-X>CaxTiO3

Distorted perovskite-type Y_<1-x>Ca_xTiO_3 is a system which moves from the Mott insulator YTiO_3(x=0) to the band insulator CaTiO_3(x=1) across the metallic phase, by controlling the Ti 3d band filling with x. In particular, Y_<1-x>Ca_xTiO_3 with x=0.39 exhibits a sharp metal-insulator transition (MIT) around 150 K (high-temperature phase : insulator, low-temperature phase : metal).We have carried out for x=0.39 the Ti 3p-3d resonant photoemission and inverse-photoemission spectroscopies (PES abd IPES) and observed the occupied and unoccupied Ti 3d densities of states, that is, the remnant of the lower and upper Hubbard bands split by the electron correlation. The experimental results revealed that the U_<eff>-value, determined from their energy separation, increases with decreasing temperature. Since the Coulomb interaction energy of the bare Ti 3d electrons is considered to be almost intraatomic value, the U_<eff> reduction reflects that the Ti 3d bands become wider at low temperature.In order to analyze the IPES spectra of x=0.39, we have measured the O 1s soft x-ray absorption spectra in comparison with the IPES spectra. The subtle structure, possibly corresponding to the coherent part in the PES spectra, seems to appear in the lower energy side of the unoccupied Ti 3d structure. This component is considered to be closely related to MIT. We have to reconfirm the existence by the IPES with higher energy resolution.We have also PES for x=0.39 using hard x-ray (several keV), which is more bulk-sensitive. The lower Hubbard band shifts to the shallower binding-energy side compared with the PES spectra with several ten eV. This suggests that the correlation effect is strong near the surface. In addition, for the metallic phase, a new component has been found in the Ti 2p PES, probably being attributed to the well screened state as observed in the Mn 2p PES of La_<1-x>Sr_xMnO_3 in the metallic phase [1].[1]K.Horiba et al., Phys.Rev.Lett. 93,236401 (2004).

畸变钙钛矿型Y_<1-x>Ca_xTiO_3是通过控制Ti的3d能带被x填充，从Mott绝缘体YTiO_3（x=0）跨越金属相移动到能带绝缘体CaTiO_3（x=1）的系统。特别是<1-x>x=0.39的Y_ Ca_xTiO_3在150 K附近表现出尖锐的金属-绝缘体转变（MIT（高温相：绝缘体，低温相：我们对x=0.39的Ti进行了3 p-3d共振光电子能谱和逆光电子能谱（PES abd IPES），观察到了Ti的3d态密度，即被电子关联分裂的上、下Hubbard带的残余部分。实验结果表明，<eff>由能量分离确定的U值随温度的降低而增大。由于裸Ti 3d电子的库仑相互作用能几乎是原子内的值，U_2<eff>还原反映了Ti 3d带在低温下变宽，为了分析x=0.39的IPES谱，我们测量了O_1 s软X射线吸收谱，并与IPES谱进行了比较。精细结构，可能对应于PES谱中的相干部分，似乎出现在未占据的Ti 3d结构的较低能量侧。这一部分被认为与麻省理工学院密切相关。我们必须通过具有更高能量分辨率的IPES来重新确认其存在。我们还使用硬X射线（几keV）对x=0.39的PES进行了验证，这对体积更敏感。较低的哈伯德带移动到较浅的结合能侧相比，PES光谱与几十eV。这表明，相关效应在地表附近很强。此外，对于金属相，在Ti 2 p PES中发现了一种新的组分，这可能是由于在金属相中La_ Sr_xMnO_3的Mn 2 p PES中观察到的良好屏蔽状态<1-x>[1]。[1]K.Horiba等人，Phys.Rev.Lett. 93，236401（2004）。

项目成果

Hole-doping and pressure effects on the metal-insulator transition in single crystals of Y_<1-x>Ca_xTiO_3 (0.37【less than or equal】x【less than or equal】0.41)

空穴掺杂和压力对Y_<1-x>Ca_xTiO_3单晶金属-绝缘体转变的影响（0.37【小于等于】x【小于等于】0.41）

• 发表时间: 2003
• 期刊: Journal of the Physical Society of Japan 72・12
• 作者: K.Umemori;M.Izawa;K.Saito;S.Sakanaka;F.Iga et al.;H.Sato et al.;H.Matsuhata et al.;H.Sato et al.;F.Iga他12名;H.Sato他19名;H.Matsuhata他6名;H.Sato他10名;M.Tsubota 他13名
• 通讯作者: M.Tsubota 他13名

M Tsubota et al.: "Hole-doping and pressure effects on the metal-insulator transition in single crystals of Y_<1-x>Ca_xTiO_3 (0.37<x<0.41)"Journal of the Physical Society of Japan. 72・12. 3182-3188 (2003)

M Tsubota 等：“Y_<1-x>Ca_xTiO_3 (0.37<x<0.41) 单晶中的空穴掺杂和压力效应”日本物理学会杂志 72・12。 3182-3188 (2003)

Valence transition of YbInCu_4 observed in hard x-ray photoemission spectra

硬X射线光电子能谱观察到的YbInCu_4的价态跃迁

• 发表时间: 2004
• 期刊: Physical Review Letters 93・24
• 作者: K.Umemori;M.Izawa;K.Saito;S.Sakanaka;H.Sato 他19名
• 通讯作者: H.Sato 他19名

Phase separation in Y_<1-x>Ca_xTiO_3 associated with the insulator to metal transition

Y_<1-x>Ca_xTiO_3 中的相分离与绝缘体到金属的转变有关

• 发表时间: 2004
• 期刊: Physical Review B 70・13
• 作者: K.Umemori;M.Izawa;K.Saito;S.Sakanaka;H.Sato 他19名;H.Matsuhata 他6名
• 通讯作者: H.Matsuhata 他6名

Electronic structure of oxysulfide (LaO)CuS and (La_<1-x>Ca_xO)Cu_<1-x>Ni_xS (x【less than or equal】0.10) studied by PES and IPES

PES和IPES研究氧硫化物(LaO)CuS和(La_<1-x>Ca_xO)Cu_<1-x>Ni_xS (x【小于等于】0.10)的电子结构

• 发表时间: 2003
• 期刊: Physical Review B 68・3
• 作者: K.Umemori;M.Izawa;K.Saito;S.Sakanaka;F.Iga et al.;H.Sato et al.;H.Matsuhata et al.;H.Sato et al.;F.Iga他12名;H.Sato他19名;H.Matsuhata他6名;H.Sato他10名;M.Tsubota 他13名;H.Sato 他12名
• 通讯作者: H.Sato 他12名