Rigorous test of electron-hole symmetry for high- Tc superconductivity using epitaxial thin films

使用外延薄膜严格测试高温超导的电子-空穴对称性

基本信息

批准号：
18340098
负责人：
NAITO Michio
金额：
$ 11.09万
依托单位：
Tokyo University of Agriculture and Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18340098/
关键词：
high- T_c superconductors electronic phase diagram electron-hole symmetry Mott-Hubbard insulators epitaxial thin films molecular beam epitaxy metal organic decomposition 酸化物高温超伝導体

项目摘要

The playground for high-T_c superconductivity is the CuO_2 plane common to both p- and n-type high-T_c superconductivity, and the electronic phase diagram of high-T_c cuprates is roughly symmetric between p- and n-type doping. Hence, it has been claimed that "electron-hole" symmetry holds for high-T_c superconductivity. Based on this claim, the doped Mott insulator scenario has been widely accepted, in which the parent material is a Mott insulator (anti-ferromagnetic insulator) and high-T_c superconductivity develops when the insulator is exposed to either p- or n-type doping. However, it should be borne in mind that electron-hole symmetry is far from obvious and even surprising. Since the mother compounds of high- T_c superconductors can be regarded as charge-transfer insulators, doped holes go on the oxygen sites but doped electrons go on the Cu sites, which should result in doped carriers with quite different natures. Furthermore it must be emphasized that the argument for the above … More "electron-hole" symmetry is based on a comparison of p- and n-type doping in different structures, namely, hole doping in the K_2NiF_4 (T) structure and electron doping in the Nd_2CuO_4 (T) structure.In principle, it is desirable to compare hole and electron doping in the same crystal structure. However, such a comparison has not yet been undertaken because it is empirically known in bulk synthesis that hole doping is possible only in octahedral (CuO_6) or pyramidal (CuO_5) cuprates whereas electron doping is possible only in square-planar (CuO_4) cuprates. For example, electron doping in the T structure or hole doping in the T' structure has never been achieved in bulk synthesis. However, in this project we report that Ce can be incorporated into the K_2NiF_4 lattice [T-La_2CuO_4 (LCO)] by employing a low-temperature synthetic route with molecular beam epitaxy (MBE) and that Sr/Ca can be incorporated into the Nd_2CuO_4 lattice by employing a low-temperature synthetic route with metal organic deposition (MOD). The former results revealed that Ce doping makes T-LCO more insulating, which is in sharp contrast to Sr (or Ba) doping in T-LCO, which makes the compound metallic and superconducting. The observed smooth increase in resistivity from the hole-doped side to the electron-doped side indicates that the electron-hole symmetry is broken in the T-phase materials. The latter result revealed that T'-RE_2CuO_4 can be superconducting even with no doping and that hole doping increases T whereas electron doping decreases T_c. Electron-hole symmetry is also broken in the T'-phase materials. Both of the results throw strong skepticism on the currently accepted "doped Mott-insulator scenario" on high- T_c superconductivity. Less

p和n型高-T_C超导性的高-T_2平面和高-T_C蛋白酶的电子phagr AM在P-and N型掺杂之间大致对称。 “对称性具有高-T_C超导性。基于EEN广泛接受，其中母体是Mott材料是Mott绝缘体（抗有效性绝缘体）和高T_C超导性时，当绝缘子暴露于任何一种P-OR N型掺杂时， y。 ABE的论点...更多的“电子”对称性是基于在ND_2CUO_4（t）结构中的k_2nif_4（t）de ping中的P-和N型差异的比较。原则上，它是在相同的晶体结构中的设计孔和电子掺杂。例如，电子掺杂仅在平面（Cuo_4）中，例如，电子掺杂在the tsh tsh tsh tsh tsh tsh中。 T-LA_2CUO_4（LCO）]通过使用分子束的低温途径与ND_2CUO_4晶格使用低温束外观，使用低温合成途径使用金属有机沉积（MOD）与T-LCO D金属和超导的SR（或BA）掺杂的鲜明对比。 . '-RE_2CUO_4 Can Be SuperConducting Eventing with no Doping and that Hole Doping Increase ELECTRON DOPING Decreases T_c. "Doped Mott-Insulator Scenario" on High- T_c SuperConductivity. Less