Superconductivity in a unique type of copper oxide

Li, W. M.; Zhao, Jinyu; Cao, Lipeng; Hu, Zhiwei; Huang, Q.; Wang, X. C.; Liu, Y.; Zhao, Guoqiang; Zhang, J.; Liu, Q. Q.; Yu, Richeng; Long, Youwen; Wu, Hui; Lin, Hong Ji; Chen, C. T.; Li, Z.; Gong, Zizhou; Guguchia, Zurab; Kim, J. S.; Stewart, G. R.; Uemura, Y. J.; Uchida, S.; Chen, Jin

doi:10.1073/pnas.1900908116

Cited by 106 publications

(69 citation statements)

References 37 publications

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“…In our Ba 2 CuO 4-y system, we have indeed observed the preedge peak in the O-K XAS spectrum as shown in figure 4 in ref. 1. This experimental observation firmly demonstrates the equivalence to La 2 CuO 4 .…”

supporting

confidence: 69%

Reply to Yamamoto: A cuprate superconductor with unconventional features

Li¹,

Zhao²,

Cao³

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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supporting

confidence: 69%

Reply to Yamamoto: A cuprate superconductor with unconventional features

Li¹,

Zhao²,

Cao³

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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“…High-Tc superconductivity in cuprates is commonly spawned in the intact two-dimensional CuO2 plane [1][2][3][4][5][6]. However, a new cuprate superconductor Ba2CuO4-δ appears to be an exception [7]. Ba2CuO4-δ crystallizes into the typical 214 layered perovskite structure [ Fig.…”

mentioning

confidence: 99%

“…Due to the missing O atoms along the middle Cu chain, the electron hopping along such a Cu chain or to its two neighboring CuO chains may be greatly suppressed (due to the absence of the Zhang-Rice singlet [18]). Figure 4(a) displays the calculated DFT bands of the = 0.67 lowest-energy 7 structure, which purely consists of the ladders. By projecting the wavefunction to atomic orbitals, the nearly flat band around 1.3 eV can be clearly attributed to the Cu in the middle (Cu2).…”

mentioning

confidence: 99%

In-plane ordering of oxygen vacancies in a high- Tc cuprate superconductor with compressed Cu-O octahedrons: An automated cluster expansion study

Weng

et al. 2020

Phys. Rev. Materials

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A recently discovered high-Tc cuprate superconductor Ba2CuO4-δ exhibits exceptional Jahn-Teller distortion, wherein the CuO6 octahedrons are compressed along the c axis. As a consequence, the O vacancies prefer to reside in the CuO2 plane, but the exact structure is not known. By combining first-principles total energy calculation with the automated structure inversion method, the effective cluster interactions of O vacancies are mapped out. Around δ=0.8, where the 73K superconductivity was observed experimentally, we predict that the ordered O vacancies slice the CuO2 plane into not only 1D chains and but also two-leg ladders. A Monte Carlo simulation is performed based on the effective cluster interaction model, showing that such an ordering pattern is stable up to ~900 K. Our results put forth a concrete structural basis to discuss the underlying superconducting mechanism.2 Main Text:High-Tc superconductivity in cuprates is commonly spawned in the intact two-dimensional CuO2 plane [1][2][3][4][5][6]. However, a new cuprate superconductor Ba2CuO4-δ appears to be an exception [7]. Ba2CuO4-δ crystallizes into the typical 214 layered perovskite structure [ Fig. 1(a)], but the CuO6 octahedrons are largely compressed along the c axis, making the in-plane Cu-O bonds weaker than the out-of-plane ones. Consequently, in contrast to the apical substitution as typically observed in other high-Tc cuprates [3][4][5][6], here the O vacancies prefer to be created in the CuO2 plane [8,9]. Surprisingly, superconductivity emerges at a very high concentration of in-plane O vacancies, when the 2D parent lattice has been strongly disrupted, and the superconducting transition temperature reaches as high as 73 K around δ=0.8.At present, the in-plane O vacancy structure is still largely unknown except for the δ=1 limit, i.e. Ba2CuO3 [8]. This stoichiometric compound as a quasi-1D Mott insulator consists of paralleled (-O-Cu-O-) chains. One can reversely consider that superconductivity emerges from Ba2CuO3+γ around γ=0.2, when excess O atoms link the 1D chains, which appears to play an important role in the 73 K superconductivity, because in other quasi-1D cuprates with charge doping only, such a high Tc has never been observed.[9-12] An interesting observation is that the atomic structure of Ba2CuO3 can be viewed as long-range ordering of in-plane O vacancies in Ba2CuO4. Ba2CuO3 shares exactly the same lattice as Ba2CuO4, with only slight changes of the lattice constants (Tab. I). The O atoms are missing along all the unidirectional (-O-Cu-O-) arrays, like cutting either the warp or the weft of a fabric. The coordinates of the remaining atoms stay almost unchanged.

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“…Finally, we comment that there is actually one more intriguing possibility for the superconducting phase observed in the high x range, that is, the superconductivity in the heavily over-doped cuprate. A few recent experimental [24,25] and theoretical [26,27] [24,26]. Another case is the superconductivity in Ba 2 CuO 4−y in which the octahedron was found in an exceptionally compressed version [25,27].…”

Section: Discussionmentioning

confidence: 99%

High-temperature interface superconductivity in bilayer copper oxide films by pulsed laser deposition

Den

Ren

et al. 2019

Sci. China Mater.

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In a seminal work, Gozar et al. reported on the high-temperature interface superconductivity in bilayers of insulating La 2 CuO 4 and metallic La 2−x Sr x CuO 4 (x=0.45). An interesting question to address is how general and robust this interface superconductivity is. In the past, the cuprate bilayers were grown in a unique atomic-layer molecular beam epitaxy system, with a Sr doping range of x≤0.47, and the atomically flat interface was thought to be indispensable. Here, we have fabricated bilayers of La 2 CuO 4 and La 2−x Sr x CuO 4 by pulsed laser deposition. We have tried to extend the nominal doping range of Sr from the previous maximum of 0.47 to the present 1.70 (the nominal Sr content in the targets). X-ray diffraction result indicates that our La 2−x Sr x CuO 4 films with x≤0.60 have very high crystalline quality; but the film crystalline structure degrades gradually with further increasing x, and finally the structure is fully lost when x reaches 1.40 and higher. Although the film quality scatters dramatically, our experiments show that there exists superconductivity for bilayers in nearly the entire over-doped Sr range, except for a non-superconducting region at x~0.80. These observations demonstrate that the interface superconductivity in copper oxides is very general and robust.

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Superconductivity in a unique type of copper oxide

Cited by 106 publications

References 37 publications

Reply to Yamamoto: A cuprate superconductor with unconventional features

Reply to Yamamoto: A cuprate superconductor with unconventional features

In-plane ordering of oxygen vacancies in a high- Tc cuprate superconductor with compressed Cu-O octahedrons: An automated cluster expansion study

High-temperature interface superconductivity in bilayer copper oxide films by pulsed laser deposition

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