Superconducting Nd _{1− x} Eu _x NiO ₂ thin films using in situ synthesis

Science Advances, Год журнала: 2023, Номер 9(27)

Опубликована: Июль 5, 2023

We report on superconductivity in Nd 1− x Eu NiO 2 using as a 4f dopant of the parent NdNiO infinite-layer compound. use an all–in situ molecular beam epitaxy reduction process to achieve superconducting phase, providing alternate method ex CaH induce nickelates. The samples exhibit step-terrace structure their surfaces, have T c onset 21 K at = 0.25, and large upper critical field that may be related doping.

Язык: Английский

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Optimizing Superconductivity: From Cuprates via Nickelates to Palladates

Physical Review Letters, Год журнала: 2023, Номер 130(16)

Опубликована: Апрель 20, 2023

Motivated by cuprate and nickelate superconductors, we perform a comprehensive study of the superconducting instability in single-band Hubbard model. We calculate spectrum transition temperature T_{c} as function filling Coulomb interaction for range hopping parameters, using dynamical vertex approximation. find sweet spot high to be at intermediate coupling, moderate Fermi surface warping, low hole doping. Combining these results with first principles calculations, neither nickelates nor cuprates are close this optimum within description. Instead, identify some palladates, notably RbSr_{2}PdO_{3} A_{2}^{'}PdO_{2}Cl_{2} (A^{'}=Ba_{0.5}La_{0.5}), virtually optimal, while others, such NdPdO_{2}, too weakly correlated.

Язык: Английский

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Limits to the strain engineering of layered square-planar nickelate thin films

Nature Communications, Год журнала: 2023, Номер 14(1)

Опубликована: Март 16, 2023

The layered square-planar nickelates, Nd$_{n+1}$Ni$_{n}$O$_{2n+2}$, are an appealing system to tune the electronic properties of nickelates via dimensionality; indeed, superconductivity was recently observed in Nd$_{6}$Ni$_{5}$O$_{12}$ thin films. Here, we investigate role epitaxial strain competing requirements for synthesis $n=3$ Ruddlesden-Popper compound, Nd$_{4}$Ni$_{3}$O$_{10}$, and subsequent reduction phase, Nd$_{4}$Ni$_{3}$O$_{8}$. We synthesize our highest quality Nd$_{4}$Ni$_{3}$O$_{10}$ films under compressive on LaAlO$_{3}$ (001), while NdGaO$_{3}$ (110) exhibits tensile strain-induced rock salt faults but retains bulk-like transport properties. A high density extended defects forms SrTiO$_{3}$ (001). Films reduced become insulating form $c$-axis canting defects, Nd$_{4}$Ni$_{3}$O$_{8}$ metallic. This work provides a pathway Nd$_{n+1}$Ni$_{n}$O$_{2n+2}$ sets limits ability engineer these compounds epitaxy.

Язык: Английский

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Synthesis and physical properties of LaNiO2 crystals

Physical Review Materials, Год журнала: 2023, Номер 7(1)

Опубликована: Янв. 30, 2023

Infinite-layer (IL) nickelates are an emerging family of superconductors whose similarities and differences to cuprate under intense debate. To date, the IL phase can only be reached via topotactic oxygen reduction perovskite phase, using H$_2$ gas or reducing agents such as CaH$_2$. While method has been widely employed on thin film polycrystalline powder samples, La$_{1-x}$Ca$_x$NiO$_3$ single-crystals with lateral dimensions up 150 $\mu$m was achieved recently, indirect contact Here we report transformation much larger LaNiO$_3$ crystals more than one millimeter, direct We characterize crystalline, magnetic, electronic properties obtained LaNiO$_{2}$ by single-crystal x-ray diffraction (XRD), magnetometry, electrical transport, photoelectron spectroscopy (XPS) measurements. The amount incorporated hydrogen due process is determined a extraction method. In addition, investigate evolution lattice parameters hydrostatic pressure 12 GPa, high-resolution synchrotron XRD. Furthermore, provide comparison several physical their counterparts.

Язык: Английский

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Experimental Progress in Superconducting Nickelates

Annual Review of Condensed Matter Physics, Год журнала: 2023, Номер 15(1), С. 305 - 324

Опубликована: Дек. 6, 2023

The superconducting nickelates were first proposed as potential analogs to the cuprate unconventional superconductors in 1999, but it took twenty years before superconductivity was successfully stabilized epitaxial thin films. Since then, a flurry of both experimental and theoretical efforts have sought understand similarities differences between two systems how they manifest macroscopic normal state properties. Although cuprates indeed share many commonalities within their respective phase diagrams, several notable also emerged, especially regarding parent compounds, electronic hybridization, fermiology. Here, we provide survey rapidly developing landscape layered nickelate superconductors, including recent progress probe not just other ordered phases these compounds.

Язык: Английский

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Topotactic hydrogen forms chains in ABO2 nickelate superconductors

Physical review. B./Physical review. B, Год журнала: 2023, Номер 107(16)

Опубликована: Апрель 10, 2023

Despite enormous experimental and theoretical efforts, obtaining generally accepted conclusions regarding the intrinsic magnetic electronic properties of superconducting nickelates remains exceptionally challenging. Experiments show a significant degree uncertainty, indicating hidden factors in synthesized films, which call for further investigations. One those is possibility intercalating hydrogen during chemical reduction process from $\mathrm{Nd}(\mathrm{La}){\mathrm{NiO}}_{3}$ to $\mathrm{Nd}(\mathrm{La}){\mathrm{NiO}}_{2}$ using ${\mathrm{CaH}}_{2}$. While has been detected samples, not much known about its distribution through crystal influence on environment. Here, we tendency toward formation one-dimensional chains infinite-layers ${\mathrm{LaNiO}}_{2}$ superconductors density-functional theory supplemented by dynamical mean-field theory. The such induces coexistence different oxidation states Ni competing phases, possibly explains recently observed charge order nickelate superconductors. Furthermore, it contributes difficulty synthesizing homogeneous determining their ground states. smoking gun detect excess flat phonon modes, are infrared active quite insensitive exact arrangement H atoms.

Язык: Английский

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Absence of hydrogen insertion into highly crystalline superconducting infinite layer nickelates

Physical Review Materials, Год журнала: 2024, Номер 8(8)

Опубликована: Авг. 12, 2024

The discovery of superconductivity in the infinite layer nickelates introduced a materials system analogous to cuprates for study unconventional superconductivity. synthesis nickelates, (${\mathrm{RNiO}}_{2}$, R = lanthanide) often uses calcium hydride (${\mathrm{CaH}}_{2}$) facilitate deintercalation apical site oxygen atoms from precursor perovskite (${\mathrm{RNiO}}_{3}$) phase via topotactic reduction. However, it remains uncertain whether use ${\mathrm{CaH}}_{2}$ results insertion hydrogen into structure, and if does, what implications are To quantify composition highly crystalline we synthesized ${\mathrm{Nd}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{NiO}}_{2}$ thin films on LSAT substrates conducted time-of-flight secondary ion mass spectroscopy measurements generate depth profiles. We compare density prepared with without ${\mathrm{SrTiO}}_{3}$ capping layer. Additionally, measure content nickelate samples at various doping levels spanning superconducting space, including underdoped, optimally doped, overdoped regime. report no significant increase between phases any measured samples. Furthermore, put an upperbound concentration our ${\mathrm{Nd}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{NiO}}_{2}{\mathrm{H}}_{0.05}$. Our imply that is not responsible emergence nickelates.

Язык: Английский

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Extensive hydrogen incorporation is not necessary for superconductivity in topotactically reduced nickelates

Nature Communications, Год журнала: 2024, Номер 15(1)

Опубликована: Авг. 27, 2024

Abstract A key open question in the study of layered superconducting nickelate films is role that hydrogen incorporation into lattice plays appearance state. Due to challenges stabilizing highly crystalline square planar films, are prepared by deposition a more stable parent compound which then transformed target phase via topotactic reaction with strongly reducing agent such as CaH 2 . Recent studies, both experimental and theoretical, have introduced possibility from may be critical for superconductivity. In this work, we use secondary ion mass spectrometry examine La 1− x X NiO / SrTiO 3 ( = Ca Sr) Nd 6 Ni 5 O 12 NdGaO along non-superconducting NdNiO (Nd,Sr)NiO We find no evidence extensive across broad range samples, including films. Theoretical calculations indicate broadly energetically unfavorable these systems, supporting our conclusion not generally required achieve state square-planar nickelates.

Язык: Английский

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Effects of different concentrations of topotactic hydrogen impurities on the electronic structure of nickelate superconductors

Physical review. B./Physical review. B, Год журнала: 2023, Номер 108(15)

Опубликована: Окт. 26, 2023

Infinite-layer nickelate superconductors have recently been discovered to share both similarities and differences with cuprate superconductors. Notably, the incorporation of hydrogen (H) through topotactic reduction has found play a critical role in their electronic structure and, consequently, superconductivity. In this study, we utilized theoretical approach combining density-functional theory impurity approximation design three characteristic multi-orbital Hubbard models representing low, moderate, high concentrations topotactic-hydrogen. Consistent experimental findings, our simulations revealed that low topotactic-hydrogen induce high-spin states ($S=1)$ are composed by holes at ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ ${d}_{{z}^{2}}$ orbitals consequently emergent intersite hopping between is unfavorable for Conversely, an optimal concentration 25% H aligns single Ni-${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ band picture superconductivity infinite-layer nickelates, demonstrating its beneficial effect on promoting superconducting behavior.

Язык: Английский

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Electronic properties of hydrogen-doped square-planar nickelates

Physical review. B./Physical review. B, Год журнала: 2024, Номер 109(15)

Опубликована: Апрель 22, 2024

The layered square-planar nickelates ${R}_{n+1}\mathrm{N}{\mathrm{i}}_{n}{\mathrm{O}}_{2n+2}$ (R: rare-earth element) hold great promise in realizing cupratelike superconductors. While the appearance of zero resistivity is extremely sensitive to concentration hydrogen($x$) infinite-layer $\mathrm{S}{\mathrm{r}}_{0.2}\mathrm{N}{\mathrm{d}}_{0.8}\mathrm{Ni}{\mathrm{O}}_{2}{\mathrm{H}}_{x}$, configurations many other $\mathrm{N}{\mathrm{d}}_{n+1}\mathrm{N}{\mathrm{i}}_{n}{\mathrm{O}}_{2n+2}{\mathrm{H}}_{x}$ and general roles H these systems are still unknown. Using first-principles calculations, we find that atoms prefer form staggered one-dimensional chains along $c$ axis, which obstructed by fluorite layer $\mathrm{N}{\mathrm{d}}_{n+1}\mathrm{N}{\mathrm{i}}_{n}{\mathrm{O}}_{2n+2}$. Importantly, charge-transfer energy between O $2p$ Ni $3d$, one key factors determining superconducting temperature cuprates, largely continuously tunable $n$ $x$ nickelates. Further, from perspective orbital hybridization polarization, quasi-two-dimensional electronic properties more pronounced for with smaller $n$, potentially facilitating superconductivity. These findings shed light on controlling provide valuable guidance experimental preparation materials.

Язык: Английский

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