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Articles by Ke-Jin Zhou
Superconducting phase diagram of multilayer square-planar nickelates
Editor’s summary Abstract Supplementary Materials References and Notes Information & Authors Metrics & Citations Check Access References Figures Tables Media Share Editor’s summary Superconductivity in the nickelates, layered compounds with notable similarities to the cuprates, can be tuned by chemical doping and by applying pressure. Pan et al. used a different approach: varying the number of NdNiO2 layers (n) sandwiched between NdO2 layers, synthesizing a series of Ndn+1NinO2n+2 compounds.
Light-triggered oxygen redox activity at the edge of cobalt oxyhydroxide for superior water oxidation
Abstract Introducing oxygen redox chemistry into cobalt oxyhydroxide effectively enhances catalytic activity by enabling direct O-O coupling, thereby bypassing the rate-limiting *OOH step in the conventional adsorbate evolution mechanism. However, the key challenge is to preserve the accessibility of non-bonding oxygen states while maintaining cobalt-oxygen covalency.
Persistent paramagnons in high-temperature infinite-layer nickelate superconductors
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Abstract The recent discovery of high-temperature superconductivity in hole-doped SmNiO2, exhibiting the record-high transition temperature Tc among infinite-layer (IL) nickelates, has opened a new avenue for exploring design principles of superconductivity. Experimentally determining the electronic structure and magnetic interactions in this new system is crucial to elucidating the mechanism behind the enhanced superconductivity.
By Yujie Yan, Ying Chan, Zhaoyang Luo, Yuehong Li, Tianren Wang, Yuetong Wu, Izabela Biało, Nurul Ainun Fitriyah, Saurav Prakash, Xing Gao, Yau Yip, Qiang Gao, Xiaolin Ren, Jaewon Choi, Jun Okamoto, Xingjiang Zhou, Zhihai Zhu, Mirian García-Fernández, Ke-Jin Zhou, Hsiao-Yu Huang, Di-Jing Huang, Johan Chang, A. Ariando, Qisi Wang, Xunyang Hong, Ganesha Channagowdra
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Nature
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Unconventional polaronic ground state in superconducting LiTi2O4 - Nature Communications
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Abstract Geometrically frustrated lattices can display a range of correlated phenomena, ranging from spin frustration and charge order to dispersionless flat bands due to quantum interference. One particularly compelling family of such materials is the half-valence spinel LiB2O4 materials. On the B-site frustrated pyrochlore sublattice, the interplay of correlated metallic behavior and charge frustration leads to a superconducting state in LiTi2O4 and heavy fermion behavior in LiV2O4.
By Zubia Hasan, Grace A. Pan, Harrison LaBollita, Austin Kaczmarek, Purnima P. Balakrishnan, Alpha T. N’Diaye, Zaher Salman, Thomas Prokscha, Andreas Suter, Alexander J. Grutter, Mirian García-Fernández, Ke-Jin Zhou, Jonathan Pelliciari, Valentina Bisogni, Darrell G. Schlom, Katja C. Nowack, Vivek Bhartiya
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Nature
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Orbital inversion and emergent lattice dynamics in infinite layer CaCoO2 - npj Quantum Materials
Abstract The layered cobaltate CaCoO2 exhibits a unique herringbone-like structure. Serving as a potential prototype for a new class of complex lattice patterns, we study the properties of CaCoO2 using X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS). Our results reveal a significant inter-plane hybridization between the Ca 4s- and Co 3d- orbitals, leading to an inversion of the textbook orbital occupation of a square planar geometry.
Resolving the orbital character of low-energy excitations in Mott insulator with intermediate spin-orbit coupling - Communications Physics
Abstract Multi-band Mott insulators with moderate spin-orbit and Hund’s coupling are key reference points for theoretical concept developments of correlated electron systems. The ruthenate Mott insulator Ca2RuO4 has therefore been intensively studied by spectroscopic probes. However, it has been challenging to resolve the fundamental excitations emerging from the hierarchy of electronic energy scales.
Decoupling Capacity Fade and Voltage Decay of Li-rich Mn-rich Cathodes by Tailoring Surface Reconstruction Pathways
Decoupling Capacity Fade and Voltage Decay of Li-rich Mn-rich Cathodes by Tailoring Surface Reconstruction Pathways Exploiting oxygen anion redox in Li-/Mn-rich layered oxides (LMR-NMCs) offers the highest capacity among cathode materials for Li-ion batteries (LIBs). However, its long-term utilization is challenging due to continuous voltage and capacity decay caused by irreversible phase transitions involving cation disordering and oxygen release.
Electronic and magnetic excitations in La3Ni2O7 - Nature Communications
Abstract High-temperature superconductivity was discovered in the pressurized nickelate La3Ni2O7 which has a unique bilayer structure and mixed valence state of nickel. The properties at ambient pressure contain crucial information of the fundamental interactions and bosons mediating superconducting pairing.
Evolution from a charge-ordered insulator to a high-temperature superconductor in Bi2Sr2(Ca,Dy)Cu2O8+δ - Nature Communications
Abstract How Cooper pairs form and condense has been the main challenge in the physics of copper-oxide high-temperature superconductors. Great efforts have been made in the ‘underdoped’ region of the phase diagram, through doping a Mott insulator or cooling a strange metal. However, there is still no consensus on how superconductivity emerges when electron-electron correlations dominate and the Fermi surface is missing.
Strain-tuned incompatible magnetic exchange-interaction in La2NiO4 - Communications Physics
Abstract Magnetic frustration is a route for novel ground states, including spin liquids and spin ices. Such frustration can be introduced through either lattice geometry or incompatible exchange interactions. Here, we find that epitaxial strain is an effective tool for tuning antiferromagnetic exchange interactions in a square-lattice system.
Resonant inelastic X-ray scattering - Nature Reviews Methods Primers
Abstract Resonant inelastic X-ray scattering (RIXS) is a powerful technique that combines spectroscopy and inelastic scattering to probe the electronic structure of materials. RIXS is based on the interaction of X-rays with matter in which the dependence on energy, momentum and polarization is introduced. The RIXS spectra can be approximated as a combination of X-ray absorption and X-ray emission. A 2D RIXS plane can be measured as a function of excitation and emission energies.
Magnetic excitations in strained infinite-layer nickelate PrNiO2 films - Nature Communications
Abstract Strongly correlated materials respond sensitively to external perturbations such as strain, pressure, and doping. In the recently discovered superconducting infinite-layer nickelates, the superconducting transition temperature can be enhanced via only ~ 1% compressive strain-tuning with the root of such enhancement still being elusive.
Trapped O2 and the origin of voltage fade in layered Li-rich cathodes - Nature Materials
Abstract Oxygen redox cathodes, such as Li1.2Ni0.13Co0.13Mn0.54O2, deliver higher energy densities than those based on transition metal redox alone. However, they commonly exhibit voltage fade, a gradually diminishing discharge voltage on extended cycling. Recent research has shown that, on the first charge, oxidation of O2− ions forms O2 molecules trapped in nano-sized voids within the structure, which can be fully reduced to O2− on the subsequent discharge.
Signature of quantum criticality in cuprates by charge density fluctuations - Nature Communications
Abstract The universality of the strange metal phase in many quantum materials is often attributed to the presence of a quantum critical point (QCP), a zero-temperature phase transition ruled by quantum fluctuations. In cuprates, where superconductivity hinders direct QCP observation, indirect evidence comes from the identification of fluctuations compatible with the strange metal phase.
Chiral phonons in quartz probed by X-rays - Nature
Abstract The concept of chirality is of great relevance in nature, from chiral molecules such as sugar to parity transformations in particle physics. In condensed matter physics, recent studies have demonstrated chiral fermions and their relevance in emergent phenomena closely related to topology1,2,3. The experimental verification of chiral phonons (bosons) remains challenging, however, despite their expected strong impact on fundamental physical properties4,5,6.
Magnetic excitations beyond the single- and double-magnons - Nature Communications
Abstract A photon carrying one unit of angular momentum can change the spin angular momentum of a magnetic system with one unit (ΔMs = ±1) at most. This implies that a two-photon scattering process can manipulate the spin angular momentum of the magnetic system with a maximum of two units. Herein we describe a triple-magnon excitation in α-Fe2O3, which contradicts this conventional wisdom that only 1- and 2-magnon excitations are possible in a resonant inelastic X-ray scattering experiment.
Critical role of hydrogen for superconductivity in nickelates - Nature
Author notes These authors contributed equally: Xiang Ding, Charles C. Tam, Xuelei Sui Authors and Affiliations School of Physics, University of Electronic Science and Technology of China, Chengdu, China Xiang Ding, Yan Zhao, Minghui Xu, Huaqian Leng, Haiyan Xiao, Xiaotao Zu & Liang Qiao Diamond Light Source, Harwell Campus, Didcot, UK Charles C. Tam, Jaewon Choi, Mirian Garcia-Fernandez, Stefano Agrestini & Ke-Jin Zhou H. H. Wills Physics Laboratory, University of Bristol, Bristol, UK Charles C.
Delocalized electron holes on oxygen in a battery cathode - Nature Energy
Abstract Oxide ions in transition metal oxide cathodes can store charge at high voltage offering a route towards higher energy density batteries. However, upon charging these cathodes, the oxidized oxide ions condense to form molecular O2 trapped in the material. Consequently, the discharge voltage is much lower than charge, leading to undesirable voltage hysteresis.
Charge density waves in infinite-layer NdNiO2 nickelates - Nature Materials
Abstract In materials science, much effort has been devoted to the reproduction of superconductivity in chemical compositions, analogous to cuprate superconductors since their discovery over 30 years ago. This approach was recently successful in realising superconductivity in infinite-layer nickelates1,2,3,4,5,6.
A broken translational symmetry state in an infinite-layer nickelate - Nature Physics
Abstract A defining signature of strongly correlated electronic systems is a rich phase diagram, which consists of multiple broken symmetries, such as magnetism, superconductivity and charge order1,2. In the recently discovered nickelate superconductors3,4,5,6,7,8,9,10, a large antiferromagnetic exchange energy has been reported, which implies the existence of strong electronic correlations11. However, signatures of a broken-symmetry state other than superconductivity have not yet been observed.
Author Correction: Spectroscopic fingerprint of charge order melting driven by quantum fluctuations in a cuprate
Author Correction: Spectroscopic fingerprint of charge order melting driven by quantum fluctuations in a cuprate W. S. Lee ORCID: orcid.org/0000-0001-7677-04211, Ke-Jin Zhou ORCID: orcid.org/0000-0001-9293-05952, M. Hepting ORCID: orcid.org/0000-0002-5824-89011, J. Li2, A. Nag2, A. C. Walters2, M. Garcia-Fernandez2, H. C. Robarts2, M. Hashimoto3, H. Lu4, B. Nosarzewski4, D. Song5, H. Eisaki5, Z. X. Shen ORCID: orcid.org/0000-0002-1454-02811,6, B. Moritz ORCID: orcid.org/0000-0002-3747-84841, J. Zaanen7 & T. P.
Spectroscopic fingerprint of charge order melting driven by quantum fluctuations in a cuprate
Abstract Copper oxide high-TC superconductors possess a number of exotic orders that coexist with or are proximal to superconductivity. Quantum fluctuations associated with these orders may account for the unusual characteristics of the normal state, and possibly affect the superconductivity1,2,3,4. Yet, spectroscopic evidence for such quantum fluctuations remains elusive.
Doping evolution of the charge excitations and electron correlations in electron-doped superconducting La2−xCexCuO4
Abstract Electron correlations play a dominant role in the charge dynamics of the cuprates. We use resonant inelastic X-ray scattering (RIXS) to track the doping dependence of the collective charge excitations in electron doped La\({}_{2-x}\)Ce\({}_{x}\)CuO\({}_{4}\) (LCCO).
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