Magnetism and Ion Diffusion in Honeycomb Layered Oxide K$_2$Ni$_2$TeO$_6$: First Time Study by Muon Spin Rotation & Neutron Scattering
N. Matsubara, E. Nocerino, O. K. Forslund, A. Zubayer, K. Papadopoulos, D. Andreica, J. Sugiyama, R. Palm, Z. Guguchia, S. P. Cottrell, T. Kamiyama, T. Saito, A… 展开作者
N. Matsubara, E. Nocerino, O. K. Forslund, A. Zubayer, K. Papadopoulos, D. Andreica, J. Sugiyama, R. Palm, Z. Guguchia, S. P. Cottrell, T. Kamiyama, T. Saito, A. Kalaboukhov, Y. Sassa, T. Masese, M. Månsson
In the quest of finding novel and efficient batteries, a great interest has raised in K-based honeycomb layer oxide materials both for their fundamental properties and potential applications. A key issue in the realization of efficient batteries based on such compounds, is to understand the K-ion diffusion mechanism. However, investigation of potassium-ion (K$^+$) dynamics in materials using magneto-spin properties has so far been challenging, due to its inherently weak nuclear magnetic moment, in contrast to other alkali ions such as lithium and sodium. Spin-polarised muons, having a high gyromagnetic ratio, make the muon spin rotation and relaxation ($μ$+SR) technique ideal for probing ions dynamics in weak magneto-spin moment materials. Here we report the magnetic properties and K+ dynamics in honeycomb layered oxide material of the K$_2$Ni$_2$TeO$_6$ using $μ$+SR measurements. Our low-temperature $μ$+SR results together with, with complementary magnetic susceptibility, find an antiferromagnetic transition at 26 K. Further $μ$+SR studies performed at higher temperatures reveal that potassium ions (K$^+$) become mobile above 250 K and the activation energy for the diffusion process is Ea = 121(13) meV. This is the first time that K+ dynamics in potassium-based battery materials has been measured using $μ$+SR. Finally our results also indicate an interesting possibility that K-ion self diffusion occurs predominantly at the surface of the powder particles. This opens future possibilities for improving ion diffusion and device performance using nano-structuring.
The nature of Na ion distribution, diffusion path, and the spin structure of $P2$-type Na$_2$Ni$_2$TeO$_6$ with a Ni honeycomb network has been explored. The nuclear density distribution of Na ions reveals a 2D chiral pattern within Na layers without breaking the original 3D crystal symmetry, which has been achieved uniquely via an inverse Fourier transform (iFT)-assisted neutron diffraction technique. The Na diffusion pathway described by the calculated iso-surface of Na ion bond valence sum (BVS) map is found consistent to a chiral diffusion mechanism. The Na site occupancy and Ni$^{2+}$ spi…
Natural abundance, impressive chemical characteristics and economic feasibility have rekindled the appeal for rechargeable sodium (Na) batteries as a practical solution for the growing energy demand, environmental sustainability and energy independence. However, the scarcity of viable positive electrode materials remains a huge impediment to the actualization of this technology. In this paper, we explore honeycomb layered oxides adopting the composition Na$_2$Ni$_{2-x}$Co$_x$TeO$_6$ ($x = 0, 0.25$ and $0.50$) as feasible positive electrode (cathode) materials for rechargeable sodium batteries …
Spin-1/2 chains with alternating antiferromagnetic (AF) and ferromagnetic (FM) couplings exhibit quantum entanglement like the integer-spin Haldane chains and might be similarly utilized for quantum computations. Such alternating AF-FM chains have been proposed to be realized in the distorted honeycomb-lattice compound Na$_2$Cu$_2$TeO$_6$, but to confirm this picture a comprehensive understanding of the exchange interactions including terms outside of the idealized model is required. Here we employ neutron scattering to study the spin dynamics in Na$_2$Cu$_2$TeO$_6$ and accurately determine th…
The magnetic and electrical properties of Co$_3$TeO$_6$ single-crystals with corundum related structure reveal a magnetic-field induced polarization below 21 K. A sharp peak in the specific heat at \approx 18 K indicates a reconstructive-type first-order phase transition. From second-harmonic generation (SHG) measurements breaking of inversion symmetry is evident and the point-group symmetry was determined as m. The temperature and magnetic-field dependence of the magnetic and electrical polarizations are discussed in the light of the SHG results.
The Johns Hopkins University（约翰斯·霍普金斯大学）；Institute for Quantum Matter, William H. Miller III Department of Physics and Astronomy（量子物质研究所，威廉·H·米勒三世物理与天文系）；Quantum Matter Institute, University of British Columbia（不列颠哥伦比亚大学量子物质研究所）；Neutron Scattering Division, Oak Ridge National Laboratory（橡树岭国家实验室中子散射部）；Department of Physics & Astronomy, University of British Columbia（不列颠哥伦比亚大学物理与天文系）；Centre for Molecular and Materials Science, TRIUMF（TRIUMF分子与材料科学中心）
In search of the potential cathode materials for sodium-ion batteries and to understand the diffusion kinetics, we report the detailed analysis of electrochemical investigation of honeycomb structured Na$_{2}$Ni$_{2}$TeO$_{6}$ material using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), galvanostatic charge-discharge (GCD) and galvanostatic intermittent titration technique (GITT). We found the discharge capacities of 82 and 77 mAhg$^{-1}$ at 0.05~C and 0.1~C current rates, respectively, and the mid-working potential of $\approx$3.9~V at 1~C and high capacity retention …
Despite being relevant to better understand the properties of honeycomb-like systems, as graphene-based compounds, the electron-phonon interaction is commonly disregarded in theoretical approaches. That is, the effects of phonon fields on \textit{interacting} Dirac electrons is an open issue, in particular when investigating long-range ordering. Thus, here we perform unbiased quantum Monte Carlo simulations to examine the Hubbard-Holstein model (HHM) in the half-filled honeycomb lattice. By performing careful finite-size scaling analysis, we identify semimetal-to-insulator quantum critical poi…
We study the spin-1 honeycomb lattice magnets with frustrated exchange interactions. The proposed microscopic spin model contains first and second neighbor Heisenberg interactions as well as the single-ion anisotropy. We establish a rich phase diagram that includes a featureless quantum paramagnet and various spin spiral states induced by the mechanism of order by quantum disorder. Although the quantum paramagnet is dubbed featureless, it is shown that, the magnetic excitations develop a contour degeneracy in the reciprocal space at the band minima. These contour degenerate excitations are res…
Honeycomb layered oxides with monovalent or divalent, monolayered cationic lattices generally exhibit myriad crystalline features encompassing rich electrochemistry, geometries and disorders, which particularly places them as attractive material candidates for next-generation energy storage applications. Herein, we report global honeycomb layered oxide compositions, ${\rm Ag_2}M_2{\rm TeO_6}$ ($M = \rm Ni, Mg, \textit{etc}.$) exhibiting $\rm Ag$ atom bilayers with sub-valent states within Ag-rich crystalline domains of ${\rm Ag_6}M_2{\rm TeO_6}$ and $\rm Ag$-deficient domains of ${\rm Ag}_{2 -…
The discovery of monolayer graphene has initiated two fertile fields in modern condensed matter physics, Dirac semimetals and atomically-thin layered materials. When these trends meet again in transition metal compounds, which possess spin and orbital degrees of freedom and strong electron correlations, more exotic phenomena are expected to emerge in the cross section of topological states of matter and Mott physics. Here, we show by using ab initio calculations that a monolayer form of transition metal trichalcogenides (TMTs), which has a honeycomb network of transition metal cations, may exh…
Spin $\frac{1}{2}$ honeycomb materials have gained substantial interest due to their exotic magnetism and possible application in quantum computing. However, in all current materials out-of-plane interactions are interfering with the in-plane order, hence a true 2D magnetic honeycomb system is still of demand. Here, we report the exfoliation of the magnetic semiconductor $α$-RuCl$_3$ into the first halide monolayers and the magnetic characterization of the spin $\frac{1}{2}$ honeycomb arrangement of turbostratically stacked RuCl$_3$ monolayers. The exfoliation is based on a reductive lithiatio…
Anyonic excitations emerging from a Kitaev spin liquid can form a basis for quantum computers. Searching for such excitations motivated intense research on the honeycomb iridate materials. However, access to a spin liquid ground state has been hindered by magnetic ordering. Cu2IrO3 is a new honeycomb iridate without thermodynamic signatures of a long-range order. Here, we use muon spin relaxation to uncover the magnetic ground state of Cu2IrO3. We find a two-component depolarization with slow and fast relaxation rates corresponding to distinct regions with dynamic and static magnetism, respect…
In the quest for materials hosting Kitaev spin liquids, much of the efforts have been focused on the fourth- and fifth-row transition metal compounds, which are spin-orbit coupling assisted Mott insulators. Here, we study the structural and magnetic properties of 3$d$ transition metal oxides, Na$_2$Co$_2$TeO$_6$ and Na$_3$Co$_2$SbO$_6$. The partial occupancy of sodium in former compound is addressed using a cluster expansion, and a honeycomb lattice of sodiums is found to be energetically favored. Starting from the \textit{ab initio} band structures, a many-body second order perturbation theor…
The physics of Mott insulators underlies diverse phenomena ranging from high temperature superconductivity to exotic magnetism. Although both the electron spin and the structure of the local orbitals play a key role in this physics, in most systems these are connected only indirectly --- via the Pauli exclusion principle and the Coulomb interaction. Iridium-based oxides (iridates) open a further dimension to this problem by introducing strong spin-orbit interactions, such that the Mott physics has a strong orbital character. In the layered honeycomb iridates this is thought to generate highly …
Very recently, a 3$d$ based honeycomb cobaltate Na$_2$Co$_2$TeO$_6$ has garnered tremendous attention due to the proposed proximity to the Kitaev spin-liquid state as its 4$d$/5$d$ counterparts. Here, we use Zn to substitute Co in a broad range and perform systematic studies on Na$_2$Co$_{2-x}$Zn$_x$TeO$_6$ by structural, magnetic, and thermodynamic measurements, and track the doping evolution of its magnetic ground states. Due to the extremely close radii of Zn$^{2+}$ and high-spin Co$^{2+}$ ions, the substitution can be easily achieved. X-ray diffractions reveal no structural transition but …
We use x-ray spectroscopy at Ir L$_3$/L$_2$ absorption edge to study powder samples of the intercalated honeycomb magnet Ag$_3$LiIr$_2$O$_6$. Based on x-ray absorption and resonant inelastic x-ray scattering measurements, and exact diagonalization calculations including next-neighbour Ir-Ir electron hoping integrals, we argue that the intercalation of Ag atoms results in a nearly itinerant electronic structure with enhanced Ir-O hybridization. As a result of the departure from the local relativistic $j_{\rm eff}\! = \!1/2$ state, we find that the relative orbital contribution to the magnetic m…
Based on first principles calculations, this study reveals that magnetism in otherwise non-magnetic materials can originate from the partial occupation of antibonding states. Since the antibonding wavefunctions are spatially antisymmetric, the spin wavefunctions should be symmteric according to the exchange antisymmetric principle of quantum mechanics. We demonstrate that this phenomenon can be observed in a graphitic carbon nitride material, $g$-C$_4$N$_3$, which can be experimentally synthesized and seen as a honeycomb structure with a vacancy. Three dangling bonds of N atoms pointing to the…
The exactly solvable Kitaev model on the honeycomb lattice has recently received enormous attention linked to the hope of achieving novel spin-liquid states with fractionalized Majorana-like excitations. In this review, we analyze the mechanism proposed by G. Jackeli and G. Khaliullin to identify Kitaev materials based on spin-orbital dependent bond interactions and provide a comprehensive overview of its implications in real materials. We set the focus on experimental results and current theoretical understanding of planar honeycomb systems (Na$_2$IrO$_3$, $α$-Li$_2$IrO$_3$, and $α$-RuCl$_3$)…
Because of its novel physical properties, two-dimensional materials have attracted great attention. From first-principle calculations and vibration frequenceis analysis, we predict a new family of two-dimensional materials based on the idea of octet stability: honeycomb lattices of pnictogens (N, P, As, Sb, Bi). The buckled structures of materials come from the sp3 hybridization. These materials have indirect band gap ranging from 0.43eV to 3.7eV. From the analysis of projected density of states, we argue that the s and p orbitals together are sufficient to describe the electronic structure un…
We investigated the magnetic properties of the ilmenite-type iridate CdIrO$_3$ with a honeycomb lattice formed by Ir$^{4+}$ ions prepared via a solid-state metathesis. The magnetization measurements with using the powder sample reveal a large effective magnetic moment and a fairly strong antiferromagnetic interaction, indicating a deviation from the Kitaev model. Considering the relationship between magnetism and crystal structure in CdIrO$_3$ with comparing with the other ilmenite-type iridates ZnIrO$_3$ and MgIrO$_3$, we conclude that insulating CdIrO$_3$ cannot be describe as a $J_{\rm eff}…
Single-crystal growth, structural characterization, and physical properties of a decorated square-kagome antiferromagnet KCu$_7$TeO$_4$(SO$_4$)$_5$Cl
Chongqing University（重庆大学）；Karlsruhe Institute of Technology（卡尔斯鲁厄理工学院）；North China Electric Power University（华北电力大学）；Renmin University of China（中国人民大学）；Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；Spallation Neutron Source Science Center（中国散裂中子源科学中心）
Beyond Kitaev exchange: $Γ'$-driven magnetism in Ag$_3$LiRh$_2$O$_6$
Felix Bloch Institute for Solid-State Physics, University of Leipzig（莱比锡大学菲利克斯·布洛赫固体物理研究所）；Technical University of Munich, TUM School of Natural Sciences, Physics Department（慕尼黑工业大学自然科学学院物理系）；Munich Center for Quantum Science and Technology (MCQST)（慕尼黑量子科学与技术中心）；Department of Physics and Center for Functional Materials, Wake Forest University（维克森林大学物理与功能材料中心）；Department of Physics, Loughborough University（拉夫堡大学物理系）；Blackett Laboratory, Imperial College London（帝国理工学院布莱克特实验室）
We report the structure, magnetic, and thermal property measurements on single crystalline and polycrystalline samples of Ru substituted honeycomb lattice iridate Na$_2$Ir$_x$Ru$_{1-x}$O$_3$ (x = 0, 0.05, 0.1, 0.15, 0.2, 0.3, 0.5). The evolution of magnetism in Na$_2$Ir$_x$Ru$_{1-x}$O$_3$ has been studied using dc and ac magnetic susceptibility, and heat capacity measurements. The parent compound Na$_2$IrO$_3$ is a spin-orbit driven Mott insulator with magnetic order of reduced moments below $T_N = 15$~K\@. In the Ru substituted samples the antiferromagnetic long range state is replaced by a s…
Spin-orbit coupled honeycomb magnets with the Kitaev interaction have received a lot of attention due to their potential of hosting exotic quantum states including quantum spin liquids. Thus far, the most studied Kitaev systems are 4d/5d-based honeycomb magnets. Recent theoretical studies predicted that 3d-based honeycomb magnets, including Na2Co2TeO6 (NCTO), could also be a potential Kitaev system. Here, we have used a combination of heat capacity, magnetization, electron spin resonance measurements alongside inelastic neutron scattering (INS) to study NCTO's quantum magnetism, and we have fo…
Honeycomb or triangular lattices were extensively studied and thought to be proper platforms for realizing quantum anomalous Hall effect (QAHE), where magnetism is usually caused by d orbitals of transition metals. Here we propose that square lattice can host three magnetic topological states, including the fully spin polarized nodal loop semimetal, QAHE and topologically trivial ferromagnetic semiconductor, in terms of the symmetry and k$\cdot$p model analyses that are materials-independent. A phase diagram is presented. We further show that the above three magnetic topological states can be …
$α$-RuCl$_3$ has been proposed recently as an excellent playground for exploring Kitaev physics on a two-dimensional (2D) honeycomb lattice. However, structural clarification of the compound has not been completed, which is crucial in understanding the physics of this system. Here, using {\it ab-initio} electronic structure calculations, we study a full three dimensional (3D) structure of $α$-RuCl$_3$ including the effects of spin-orbit coupling (SOC) and electronic correlations. Three major results are as follows; i) SOC suppresses dimerization of Ru atoms, which exists in other Ru compounds …
We report the crystal structure and magnetic behavior of the $4d^3$ spin-$\frac32$ silicophosphate MoP$_3$SiO$_{11}$ studied by high-resolution synchrotron x-ray diffraction, neutron diffraction, thermodynamic measurements, and ab initio band-structure calculations. Our data revise the crystallographic symmetry of this compound and establish its rhombohedral space group ($R\bar 3c$) along with the geometrically perfect honeycomb lattice of the Mo$^{3+}$ ions residing in disconnected MoO$_6$ octahedra. Long-range antiferromagnetic order with the propagation vector $\mathbf k=0$ observed below $…
Heisenberg interactions are ubiquitous in magnetic materials and have been prevailing in modeling and designing quantum magnets. Bond-directional interactions offer a novel alternative to Heisenberg exchange and provide the building blocks of the Kitaev model, which has a quantum spin liquid (QSL) as its exact ground state. Honeycomb iridates, A2IrO3 (A=Na,Li), offer potential realizations of the Kitaev model, and their reported magnetic behaviors may be interpreted within the Kitaev framework. However, the extent of their relevance to the Kitaev model remains unclear, as evidence for bond-dir…
Low Energy Excitations in a [4]Triangulene Honeycomb Antiferromagnet
University of California, Berkeley（加州大学伯克利分校）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；Kavli Energy NanoScience Institute at the University of California Berkeley and the Lawrence Berkeley National Laboratory（加州大学伯克利分校与劳伦斯伯克利国家实验室卡弗里能源纳米科学研究所）
The ruthenium halide $α$-RuCl$_{3}$ is a promising candidate for a Kitaev spin liquid. However, the microscopic model describing $α$-RuCl$_{3}$ is still debated partly because of a lack of analogue materials for $α$-RuCl$_{3}$, which prevents tracking of electronic properties as functions of controlled interaction parameters. Here, we report a successful synthesis of RuBr$_{3}$. The material RuBr$_{3}$~possesses BiI$_3$-type structure (space group: $R\overline{3}$) where Ru$^{3+}$ form an ideal honeycomb lattice. Although RuBr$_{3}$ has a negative Weiss temperature, it undergoes a zigzag antif…
It is known that there is a wide class of quasi-two-dimensional graphenelike nanomaterials which in many respects can outperform graphene. So, here in addition to graphene, the attention is directed to stanene (buckled honeycomb structure) and phosphorene (puckered honeycomb structure). It is shown that, depending on the doping, these materials can have magnetically ordered edges. Computed diagrams of magnetic phases illustrate that, on the one hand, n-type doped narrow zigzag nanoribbons of graphene and stanene have antiferromagnetically aligned magnetic moments between the edges. On the othe…
The current family of experimentally realized two-dimensional magnetic materials consist of 3$d$ transition metals with very weak spin-orbit coupling. In contrast, we report a new platform in a chemically bonded and layered 4$d$ oxide, with strong electron correlations and competing spin-orbit coupling. We synthesize ultra-thin sheets of SrRu$_2$O$_6$ using scalable liquid exfoliation. These exfoliated sheets are characterized by complementary experimental and theoretical techniques. The thickness of the nano-sheets varies between three to five monolayers, and within the first-principles calcu…
Recent observations of novel spin-orbit coupled states have generated tremendous interest in $4d/5d$ transition metal systems. A prime example is the $J_{\text{eff}}=\frac{1}{2}$ state in iridate materials and $α$-RuCl$_{3}$ that drives Kitaev interactions. Here, by tuning the competition between spin-orbit interaction ($λ_{\text{SOC}}$) and trigonal crystal field splitting ($Δ_\text{T}$), we restructure the spin-orbital wave functions into a novel $μ=\frac{1}{2}$ state that drives Ising interactions. This is done via a topochemical reaction that converts Li$_{2}$RhO$_{3}$ to Ag$_{3}$LiRh$_{2}…
Electronic and topological properties of Ce-based honeycomb ferromagnet Ce$_2$Zn$_6$Ge$_3$
New Cornerstone Science Laboratory, Center for Correlated Matter and School of Physics, Zhejiang University（新Cornerstone科学实验室，关联物质中心与物理学院，浙江大学）；Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences（凝聚态物理北京国家实验室，物理研究所，中国科学院）；School of Physical Sciences, University of Chinese Academy of Sciences（物理科学学院，中国科学院大学）；Institute of Fundamental and Transdisciplinary Research, Zhejiang University（基础与交叉研究 institute，浙江大学）；State Key Laboratory of Silicon and Advanced Semiconductor Materials, Zhejiang University（硅与先进半导体材料国家重点实验室，浙江大学）；Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China（先进微结构协同创新中心）
