1
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Koval AM, Jenness GR, Schutt TC, Kosgei GK, Fernando PUAI, Shukla MK. Periodic DFT calculations to compute the attributes of a quantum material: honeycomb ruthenium trichloride. Phys Chem Chem Phys 2024; 26:19369-19379. [PMID: 38967480 DOI: 10.1039/d4cp01383b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/06/2024]
Abstract
Quantum spin liquids (QSLs) have become prominent materials of interest in the pursuit of fault-tolerant materials for quantum computing applications. This is due to the fact that these materials are theorized to host an interesting variety of quantum phenomena such as quasi-particles that may behave as anyons as a result of the high entangled nature of the spin states within the systems. Computing the electronic and magnetic properties of these materials is necessary in order to understand the underlying interactions of the materials. In this paper, the structural, electronic, and magnetic properties including lattice parameters, bandgap, Heisenberg coupling constants, and Curie temperatures for α-RuCl3, a promising candidate for the Kitaev QSL model, are computed using periodic density functional theory. Furthermore, various parameters of the calculations (i.e. functional choice, basis set, k-point density, and Hubbard correction) are varied in order to determine what effect, if any, the computational setup has on the computed properties. The results of this study indicate that PBE functional with Hubbard corrections of 1.5-2.5 eV with a k-point density of 3.0 points per Å-1 appear to be the best parameters to compute Heisenberg coupling constants for α-RuCl3. These parameters with the addition of spin orbit coupling works well for computing Curie temperatures for α-RuCl3. Distinct differences are noted in the computations of the bulk structure vs. monolayer structures, indicating that interactions between the layers play a role in the material properties and changes to the inter-layer spacing may result in interesting and unique magnetic properties that require further investigation.
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Affiliation(s)
- Ashlyn M Koval
- Simetri Inc., 7005 University Blvd, Winter Park, Florida 32792, USA
- Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee 37830, USA
| | - Glen R Jenness
- Environmental Laboratory, US Army Engineer Research and Development Center, 3909 Halls Ferry Road, Vicksburg, Mississippi 39180, USA.
| | - Timothy C Schutt
- Environmental Laboratory, US Army Engineer Research and Development Center, 3909 Halls Ferry Road, Vicksburg, Mississippi 39180, USA.
| | - Gilbert K Kosgei
- Environmental Laboratory, US Army Engineer Research and Development Center, 3909 Halls Ferry Road, Vicksburg, Mississippi 39180, USA.
| | | | - Manoj K Shukla
- Environmental Laboratory, US Army Engineer Research and Development Center, 3909 Halls Ferry Road, Vicksburg, Mississippi 39180, USA.
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2
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Chen X, Xu S, Shabani S, Zhao Y, Fu M, Millis AJ, Fogler MM, Pasupathy AN, Liu M, Basov DN. Machine Learning for Optical Scanning Probe Nanoscopy. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2109171. [PMID: 36333118 DOI: 10.1002/adma.202109171] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 07/09/2022] [Indexed: 06/16/2023]
Abstract
The ability to perform nanometer-scale optical imaging and spectroscopy is key to deciphering the low-energy effects in quantum materials, as well as vibrational fingerprints in planetary and extraterrestrial particles, catalytic substances, and aqueous biological samples. These tasks can be accomplished by the scattering-type scanning near-field optical microscopy (s-SNOM) technique that has recently spread to many research fields and enabled notable discoveries. Herein, it is shown that the s-SNOM, together with scanning probe research in general, can benefit in many ways from artificial-intelligence (AI) and machine-learning (ML) algorithms. Augmented with AI- and ML-enhanced data acquisition and analysis, scanning probe optical nanoscopy is poised to become more efficient, accurate, and intelligent.
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Affiliation(s)
- Xinzhong Chen
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Suheng Xu
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Sara Shabani
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Yueqi Zhao
- Department of Physics, University of California at San Diego, La Jolla, CA, 92093-0319, USA
| | - Matthew Fu
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Andrew J Millis
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Michael M Fogler
- Department of Physics, University of California at San Diego, La Jolla, CA, 92093-0319, USA
| | - Abhay N Pasupathy
- Department of Physics, Columbia University, New York, NY, 10027, USA
| | - Mengkun Liu
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794, USA
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - D N Basov
- Department of Physics, Columbia University, New York, NY, 10027, USA
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3
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Han X, You JY, Wu S, Li R, Feng YP, Loh KP, Zhao X. Atomically Unveiling an Atlas of Polytypes in Transition-Metal Trihalides. J Am Chem Soc 2023; 145:3624-3635. [PMID: 36735914 DOI: 10.1021/jacs.2c12801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Transition-metal trihalides MX3 (M = Cr, Ru; X = Cl, Br, and I) belong to a family of novel two-dimensional (2D) magnets that can exhibit topological magnons and electromagnetic properties, thus affording great promises in next-generation spintronic devices. Rich magnetic ground states observed in the MX3 family are believed to be strongly correlated to the signature Kagome lattice and interlayer van der Waals coupling raised from distinct stacking orders. However, the intrinsic air instability of MX3 makes their direct atomic-scale analysis challenging. Therefore, information on the stacking-registry-dependent magnetism for MX3 remains elusive, which greatly hinders the engineering of desired phases. Here, we report a nondestructive transfer method and successfully realize an intact transfer of bilayer MX3, as evidenced by scanning transmission electron microscopy (STEM). After surveying hundreds of MX3 thin flakes, we provide a full spectrum of stacking orders in MX3 with atomic precision and calculated their associated magnetic ground states, unveiled by combined STEM and density functional theory (DFT). In addition to well-documented phases, we discover a new monoclinic C2/c phase in the antiferromagnetic (AFM) structure widely existing in MX3. Rich stacking polytypes, including C2/c, C2/m, R3̅, P3112, etc., provide rich and distinct magnetic ground states in MX3. Besides, a high density of strain soliton boundaries is consistently found in all MX3, combined with likely inverted structures, allowing AFM to ferromagnetic (FM) transitions in most MX3. Therefore, our study sheds light on the structural basis of diverse magnetic orders in MX3, paving the way for modulating magnetic couplings via stacking engineering.
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Affiliation(s)
- Xiaocang Han
- School of Materials Science and Engineering, Peking University, Beijing100871, China
| | - Jing-Yang You
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551Singapore
| | - Shengqiang Wu
- School of Materials Science and Engineering, Peking University, Beijing100871, China
| | - Runlai Li
- College of Polymer Science & Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu610065, China
| | - Yuan Ping Feng
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551Singapore
| | - Kian Ping Loh
- Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Hong Kong SAR, 999077, China
| | - Xiaoxu Zhao
- School of Materials Science and Engineering, Peking University, Beijing100871, China
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4
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Liu Y, Kelley KP, Funakubo H, Kalinin SV, Ziatdinov M. Exploring Physics of Ferroelectric Domain Walls in Real Time: Deep Learning Enabled Scanning Probe Microscopy. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2203957. [PMID: 36065001 PMCID: PMC9631058 DOI: 10.1002/advs.202203957] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2022] [Revised: 08/12/2022] [Indexed: 05/25/2023]
Abstract
The functionality of ferroelastic domain walls in ferroelectric materials is explored in real-time via the in situ implementation of computer vision algorithms in scanning probe microscopy (SPM) experiment. The robust deep convolutional neural network (DCNN) is implemented based on a deep residual learning framework (Res) and holistically nested edge detection (Hed), and ensembled to minimize the out-of-distribution drift effects. The DCNN is implemented for real-time operations on SPM, converting the data stream into the semantically segmented image of domain walls and the corresponding uncertainty. Further the pre-defined experimental workflows perform piezoresponse spectroscopy measurement on thus discovered domain walls, and alternating high- and low-polarization dynamic (out-of-plane) ferroelastic domain walls in a PbTiO3 (PTO) thin film and high polarization dynamic (out-of-plane) at short ferroelastic walls (compared with long ferroelastic walls) in a lead zirconate titanate (PZT) thin film is reported. This work establishes the framework for real-time DCNN analysis of data streams in scanning probe and other microscopies and highlights the role of out-of-distribution effects and strategies to ameliorate them in real time analytics.
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Affiliation(s)
- Yongtao Liu
- Center for Nanophase Materials SciencesOak Ridge National LaboratoryOak RidgeTN37830USA
| | - Kyle P. Kelley
- Center for Nanophase Materials SciencesOak Ridge National LaboratoryOak RidgeTN37830USA
| | - Hiroshi Funakubo
- Department of Material Science and EngineeringTokyo Institute of TechnologyYokohama226‐8502Japan
| | - Sergei V. Kalinin
- Department of Materials Science and EngineeringUniversity of TennesseeKnoxvilleTN37996USA
| | - Maxim Ziatdinov
- Center for Nanophase Materials SciencesOak Ridge National LaboratoryOak RidgeTN37830USA
- Computational Sciences and Engineering DivisionOak Ridge National LaboratoryOak RidgeTN37830USA
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5
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Wang Z, Liu L, Zheng H, Zhao M, Yang K, Wang C, Yang F, Wu H, Gao C. Direct observation of the Mottness and p-d orbital hybridization in the epitaxial monolayer α-RuCl 3. NANOSCALE 2022; 14:11745-11749. [PMID: 35917194 DOI: 10.1039/d2nr02827a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
α-RuCl3, a promising material to accomplish the Kitaev honeycomb model, has attracted enormous interest recently. Mottness and p-d bonds play vital roles in generating Kitaev interactions and underpinning the potential exotic states of quantum magnets, and the van der Waals monolayer is considered to be a better platform to approach a two-dimensional Kitaev model than the bulk. Here, we worked out the growth art of an α-RuCl3 monolayer on a graphite substrate and studied its electronic structure, particularly the delicate orbital occupations, through scanning tunneling microscopy and spectroscopy. An in-plane lattice expansion of 2.67 ± 0.83% is observed and the pronounced t2g-pπ and eg-pσ hybridization are visualized. The Mott nature is unveiled by an ∼0.6 eV full gap at the Fermi level located inside the t2g-pπ manifold which is further verified by the density functional theory calculations. The monolayer phase of α-RuCl3 fulfills the a priori criteria of recent theoretical predictions of tuning the relevant properties in this material and provides a novel platform to explore the Kitaev physics.
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Affiliation(s)
- Zhongjie Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, China.
| | - Lu Liu
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, China.
- Laboratory for Computational Physical Sciences (MOE), Fudan University, Shanghai 200438, China
| | - Haoran Zheng
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, China.
| | - Meng Zhao
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, China.
| | - Ke Yang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, China.
- Laboratory for Computational Physical Sciences (MOE), Fudan University, Shanghai 200438, China
| | - Chunzheng Wang
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, China.
| | - Fang Yang
- Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Songhu Rd. 2005, Shanghai 200438, China
- Zhangjiang Fudan International Innovation Center, Fudan University, Shanghai 201210, China
| | - Hua Wu
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, China.
- Laboratory for Computational Physical Sciences (MOE), Fudan University, Shanghai 200438, China
- Shanghai Qi Zhi Institute, Shanghai 200232, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Chunlei Gao
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, China.
- Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Songhu Rd. 2005, Shanghai 200438, China
- Zhangjiang Fudan International Innovation Center, Fudan University, Shanghai 201210, China
- Shanghai Qi Zhi Institute, Shanghai 200232, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
- Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
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6
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Mahatara S, Kiefer B. Layer dependent magnetism and topology in monolayer and bilayers Re X3( X=Br, I). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:455801. [PMID: 34375966 DOI: 10.1088/1361-648x/ac1c2e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Accepted: 08/10/2021] [Indexed: 06/13/2023]
Abstract
The realization of robust intrinsic ferromagnetism in two-dimensional materials with the possibility to support topologically non-trivial states has provided the fertile ground for novel physics and next-generation spintronics and quantum computing applications. In this contribution, we investigated the formation of topological states and magnetism in monolayer and bilayer systems of ReX3(X= Br, I), with PBE, ACBN0 (self-consistent Hubbard-U), excluding/including van der Waals (vdW) corrections and/or spin-orbit coupling. Bulk ReX3(X= Br, I) is predicted to crystallize in space groupR3¯(#148), similar to CrI3, with monolayer exfoliation energies that are comparable or less than that of graphite. The topological character of the monolayer and bilayer systems of ReX3(X= Br, I) is derived from anomalous Hall conductivity computations. Topologically non-trivial states in ReX3(X= Br, I) are absent in the Hubbard-Ucomputations if vdW interactions are included, a prediction that is attributed to the large Hubbard-Udifference between the chemical constituents, ΔU∼ 1.5-1.6 eV, and a significant ∼2.0%-3.6% compressive in-plane strain introduced by vdW interactions. In contrast to the fragile and likely absent topological states in ReX3(X= Br, I), magnetic properties are robust and independent of the level of theory: ferromagnetic monolayers are coupled antiferromagnetically to bilayers, with an energy separation between ferromagnetic and antiferromagnetic bilayer spin configurations that could be as low as 0.02 meV/Re (f= 4.8 GHz), well within the microwave range. This suggests that layer dependent magnetism in ReX3(X= Br, I) may support a microwave controllable magnetic qubit, consisting of a superposition of antiferromagnetic and ferromagnetic bilayer states.
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Affiliation(s)
- Sharad Mahatara
- Department of Physics, New Mexico State University, Las Cruces, NM 88003, United States of America
| | - Boris Kiefer
- Department of Physics, New Mexico State University, Las Cruces, NM 88003, United States of America
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7
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Kalinin SV, Dyck O, Jesse S, Ziatdinov M. Exploring order parameters and dynamic processes in disordered systems via variational autoencoders. SCIENCE ADVANCES 2021; 7:eabd5084. [PMID: 33883126 PMCID: PMC11426202 DOI: 10.1126/sciadv.abd5084] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 03/05/2021] [Indexed: 06/12/2023]
Abstract
We suggest and implement an approach for the bottom-up description of systems undergoing large-scale structural changes and chemical transformations from dynamic atomically resolved imaging data, where only partial or uncertain data on atomic positions are available. This approach is predicated on the synergy of two concepts, the parsimony of physical descriptors and general rotational invariance of noncrystalline solids, and is implemented using a rotationally invariant extension of the variational autoencoder applied to semantically segmented atom-resolved data seeking the most effective reduced representation for the system that still contains the maximum amount of original information. This approach allowed us to explore the dynamic evolution of electron beam-induced processes in a silicon-doped graphene system, but it can be also applied for a much broader range of atomic scale and mesoscopic phenomena to introduce the bottom-up order parameters and explore their dynamics with time and in response to external stimuli.
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Affiliation(s)
- Sergei V Kalinin
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
| | - Ondrej Dyck
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Stephen Jesse
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Maxim Ziatdinov
- Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
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8
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Abstract
Quantum spin liquids are an exciting playground for exotic physical phenomena and emergent many-body quantum states. The realization and discovery of quantum spin liquid candidate materials and associated phenomena lie at the intersection of solid-state chemistry, condensed matter physics, and materials science and engineering. In this review, we provide the current status of the crystal chemistry, synthetic techniques, physical properties, and research methods in the field of quantum spin liquids. We highlight a number of specific quantum spin liquid candidate materials and their structure-property relationships, elucidating their fascinating behavior and connecting it to the intricacies of their structures. Furthermore, we share our thoughts on defects and their inevitable presence in materials, of which quantum spin liquids are no exception, which can complicate the interpretation of characterization of these materials, and urge the community to extend their attention to materials preparation and data analysis, cognizant of the impact of defects. This review was written with the intention of providing guidance on improving the materials design and growth of quantum spin liquids, and to paint a picture of the beauty of the underlying chemistry of this exciting class of materials.
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Affiliation(s)
- Juan R Chamorro
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States.,Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Tyrel M McQueen
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States.,Institute for Quantum Matter, Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, United States.,Department of Materials Science and Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Thao T Tran
- Department of Chemistry, Clemson University, Clemson, South Carolina 29634, United States
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9
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Bergeron H, Lebedev D, Hersam MC. Polymorphism in Post-Dichalcogenide Two-Dimensional Materials. Chem Rev 2021; 121:2713-2775. [PMID: 33555868 DOI: 10.1021/acs.chemrev.0c00933] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Two-dimensional (2D) materials exhibit a wide range of atomic structures, compositions, and associated versatility of properties. Furthermore, for a given composition, a variety of different crystal structures (i.e., polymorphs) can be observed. Polymorphism in 2D materials presents a fertile landscape for designing novel architectures and imparting new functionalities. The objective of this Review is to identify the polymorphs of emerging 2D materials, describe their polymorph-dependent properties, and outline methods used for polymorph control. Since traditional 2D materials (e.g., graphene, hexagonal boron nitride, and transition metal dichalcogenides) have already been studied extensively, the focus here is on polymorphism in post-dichalcogenide 2D materials including group III, IV, and V elemental 2D materials, layered group III, IV, and V metal chalcogenides, and 2D transition metal halides. In addition to providing a comprehensive survey of recent experimental and theoretical literature, this Review identifies the most promising opportunities for future research including how 2D polymorph engineering can provide a pathway to materials by design.
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Affiliation(s)
- Hadallia Bergeron
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Dmitry Lebedev
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Mark C Hersam
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States.,Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States.,Department of Electrical and Computer Engineering, Northwestern University, Evanston, Illinois 60208, United States
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10
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Pereira RG, Egger R. Electrical Access to Ising Anyons in Kitaev Spin Liquids. PHYSICAL REVIEW LETTERS 2020; 125:227202. [PMID: 33315455 DOI: 10.1103/physrevlett.125.227202] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 11/03/2020] [Indexed: 06/12/2023]
Abstract
We show that spin-spin correlations in a non-Abelian Kitaev spin liquid are associated with a characteristic inhomogeneous charge density distribution in the vicinity of Z_{2} vortices. This density profile and the corresponding local electric fields are observable, e.g., by means of surface probe techniques. Conversely, by applying bias voltages to several probe tips, one can stabilize Ising anyons (Z_{2} vortices harboring a Majorana zero mode) at designated positions, where we predict a clear Majorana signature in energy absorption spectroscopy.
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Affiliation(s)
- Rodrigo G Pereira
- International Institute of Physics and Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Natal, RN, 59078-970, Brazil
| | - Reinhold Egger
- Institut für Theoretische Physik, Heinrich-Heine-Universität, D-40225 Düsseldorf, Germany
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11
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Wang H, Srot V, Jiang X, Yi M, Wang Y, Boschker H, Merkle R, Stark RW, Mannhart J, van Aken PA. Probing Charge Accumulation at SrMnO 3/SrTiO 3 Heterointerfaces via Advanced Electron Microscopy and Spectroscopy. ACS NANO 2020; 14:12697-12707. [PMID: 32910642 PMCID: PMC7596774 DOI: 10.1021/acsnano.0c01545] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 09/10/2020] [Indexed: 06/11/2023]
Abstract
The last three decades have seen a growing trend toward studying the interfacial phenomena in complex oxide heterostructures. Of particular concern is the charge distribution at interfaces, which is a crucial factor in controlling the interface transport behavior. However, the study of the charge distribution is very challenging due to its small length scale and the intricate structure and chemistry at interfaces. Furthermore, the underlying origin of the interfacial charge distribution has been rarely studied in-depth and is still poorly understood. Here, by a combination of aberration-corrected scanning transmission electron microscopy (STEM) and spectroscopy techniques, we identify the charge accumulation in the SrMnO3 (SMO) side of SrMnO3/SrTiO3 heterointerfaces and find that the charge density attains the maximum of 0.13 ± 0.07 e-/unit cell (uc) at the first SMO monolayer. Based on quantitative atomic-scale STEM analyses and first-principle calculations, we explore the origin of interfacial charge accumulation in terms of epitaxial strain-favored oxygen vacancies, cationic interdiffusion, interfacial charge transfer, and space-charge effects. This study, therefore, provides a comprehensive description of the charge distribution and related mechanisms at the SMO/STO heterointerfaces, which is beneficial for the functionality manipulation via charge engineering at interfaces.
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Affiliation(s)
- Hongguang Wang
- Max
Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Vesna Srot
- Max
Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Xijie Jiang
- Institute
of Materials Science, Technische Universität
Darmstadt, 64287 Darmstadt, Germany
| | - Min Yi
- Institute
of Materials Science, Technische Universität
Darmstadt, 64287 Darmstadt, Germany
- State
Key Lab of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics
(NUAA), Nanjing 210016, China
| | - Yi Wang
- Max
Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Hans Boschker
- Max
Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Rotraut Merkle
- Max
Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Robert W. Stark
- Institute
of Materials Science, Technische Universität
Darmstadt, 64287 Darmstadt, Germany
| | - Jochen Mannhart
- Max
Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - Peter A. van Aken
- Max
Planck Institute for Solid State Research, 70569 Stuttgart, Germany
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12
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Minakawa T, Murakami Y, Koga A, Nasu J. Majorana-Mediated Spin Transport in Kitaev Quantum Spin Liquids. PHYSICAL REVIEW LETTERS 2020; 125:047204. [PMID: 32794825 DOI: 10.1103/physrevlett.125.047204] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 06/26/2020] [Indexed: 06/11/2023]
Abstract
We study the spin transport through the quantum spin liquid (QSL) by investigating the real-time and real-space dynamics of the Kitaev spin system with zigzag edges using the time-dependent Majorana mean-field theory. After the magnetic-field pulse is introduced to one of the edges, spin moments are excited in the opposite edge region although spin moments are never induced in the Kitaev QSL region. This unusual spin transport originates from the fact that the S=1/2 spins are fractionalized into the itinerant and localized Majorana fermions in the Kitaev system. Although both Majorana fermions are excited by the magnetic pulse, only the itinerant ones flow through the bulk regime without spin excitations, resulting in the spin transport in the Kitaev system despite the presence of a nonzero spin gap. We also demonstrate that this phenomenon can be observed in the system with small Heisenberg interactions using the exact diagonalization.
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Affiliation(s)
- Tetsuya Minakawa
- Department of Physics, Tokyo Institute of Technology, Meguro, Tokyo 152- 8551, Japan
| | - Yuta Murakami
- Department of Physics, Tokyo Institute of Technology, Meguro, Tokyo 152- 8551, Japan
| | - Akihisa Koga
- Department of Physics, Tokyo Institute of Technology, Meguro, Tokyo 152- 8551, Japan
| | - Joji Nasu
- Department of Physics, Yokohama National University, Hodogaya, Yokohama 240-8501, Japan
- PRESTO, Japan Science and Technology Agency, Honcho Kawaguchi, Saitama 332-0012, Japan
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13
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Motome Y, Sano R, Jang S, Sugita Y, Kato Y. Materials design of Kitaev spin liquids beyond the Jackeli-Khaliullin mechanism. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:404001. [PMID: 32235048 DOI: 10.1088/1361-648x/ab8525] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 03/31/2020] [Indexed: 06/11/2023]
Abstract
The Kitaev spin liquid provides a rare example of well-established quantum spin liquids in more than one dimension. It is obtained as the exact ground state of the Kitaev spin model with bond-dependent anisotropic interactions. The peculiar interactions can be yielded by the synergy of spin-orbit coupling and electron correlations for specific electron configuration and lattice geometry, which is known as the Jackeli-Khaliullin mechanism. Based on this mechanism, there has been a fierce race for the materialization of the Kitaev spin liquid over the last decade, but the candidates have been still limited mostly to 4d- and 5d-electron compounds including cations with the low-spind5electron configuration, such as Ir4+and Ru3+. Here we discuss recent efforts to extend the material perspective beyond the Jackeli-Khaliullin mechanism, by carefully reexamining the two requisites, formation of thejeff= 1/2 doublet and quantum interference between the exchange processes, for not onlyd- but alsof-electron systems. We present three examples: the systems including Co2+and Ni3+with the high-spind7electron configuration, Pr4+with thef1-electron configuration, and polar asymmetry in the lattice structure. In particular, the latter two are intriguing since they may realize the antiferromagnetic Kitaev interactions, in contrast to the ferromagnetic ones in the existing candidates. This partial overview would stimulate further material exploration of the Kitaev spin liquids and its topological properties due to fractional excitations.
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Affiliation(s)
- Yukitoshi Motome
- Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
| | - Ryoya Sano
- Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
| | - Seonghoon Jang
- Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
| | - Yusuke Sugita
- Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
| | - Yasuyuki Kato
- Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
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14
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Gibson QD, Manning TD, Zanella M, Zhao T, Murgatroyd PAE, Robertson CM, Jones LAH, McBride F, Raval R, Cora F, Slater B, Claridge JB, Dhanak VR, Dyer MS, Alaria J, Rosseinsky MJ. Modular Design via Multiple Anion Chemistry of the High Mobility van der Waals Semiconductor Bi 4O 4SeCl 2. J Am Chem Soc 2020; 142:847-856. [PMID: 31825213 PMCID: PMC7007234 DOI: 10.1021/jacs.9b09411] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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Making new van der
Waals materials with electronic or magnetic
functionality is a chemical design challenge for the development of
two-dimensional nanoelectronic and energy conversion devices. We present
the synthesis and properties of the van der Waals material Bi4O4SeCl2, which is a 1:1 superlattice
of the structural units present in the van der Waals insulator BiOCl
and the three-dimensionally connected semiconductor Bi2O2Se. The presence of three anions gives the new structure
both the bridging selenide anion sites that connect pairs of Bi2O2 layers in Bi2O2Se and
the terminal chloride sites that produce the van der Waals gap in
BiOCl. This retains the electronic properties of Bi2O2Se while reducing the dimensionality of the bonding network
connecting the Bi2O2Se units to allow exfoliation
of Bi4O4SeCl2 to 1.4 nm height. The
superlattice structure is stabilized by the configurational entropy
of anion disorder across the terminal and bridging sites. The reduction
in connective dimensionality with retention of electronic functionality
stems from the expanded anion compositional diversity.
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Affiliation(s)
- Quinn D Gibson
- Department of Chemistry , University of Liverpool , Crown St , Liverpool L69 7ZD , United Kingdom
| | - Troy D Manning
- Department of Chemistry , University of Liverpool , Crown St , Liverpool L69 7ZD , United Kingdom
| | - Marco Zanella
- Department of Chemistry , University of Liverpool , Crown St , Liverpool L69 7ZD , United Kingdom
| | - Tianqi Zhao
- Department of Chemistry , University College London , 20 Gordon St, Kings Cross , London WC1H 0AJ , United Kingdom
| | - Philip A E Murgatroyd
- Department of Physics , University of Liverpool , Oxford St , Liverpool L69 7ZE , United Kingdom
| | - Craig M Robertson
- Department of Chemistry , University of Liverpool , Crown St , Liverpool L69 7ZD , United Kingdom
| | - Leanne A H Jones
- Department of Physics , University of Liverpool , Oxford St , Liverpool L69 7ZE , United Kingdom
| | - Fiona McBride
- Department of Chemistry , University of Liverpool , Crown St , Liverpool L69 7ZD , United Kingdom
| | - Rasmita Raval
- Department of Chemistry , University of Liverpool , Crown St , Liverpool L69 7ZD , United Kingdom
| | - Furio Cora
- Department of Chemistry , University College London , 20 Gordon St, Kings Cross , London WC1H 0AJ , United Kingdom
| | - Ben Slater
- Department of Chemistry , University College London , 20 Gordon St, Kings Cross , London WC1H 0AJ , United Kingdom
| | - John B Claridge
- Department of Chemistry , University of Liverpool , Crown St , Liverpool L69 7ZD , United Kingdom
| | - Vin R Dhanak
- Department of Physics , University of Liverpool , Oxford St , Liverpool L69 7ZE , United Kingdom
| | - Matthew S Dyer
- Department of Chemistry , University of Liverpool , Crown St , Liverpool L69 7ZD , United Kingdom
| | - Jonathan Alaria
- Department of Physics , University of Liverpool , Oxford St , Liverpool L69 7ZE , United Kingdom
| | - Matthew J Rosseinsky
- Department of Chemistry , University of Liverpool , Crown St , Liverpool L69 7ZD , United Kingdom
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15
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Reschke S, Mayr F, Widmann S, von Nidda HAK, Tsurkan V, Eremin MV, Do SH, Choi KY, Wang Z, Loidl A. Sub-gap optical response in the Kitaev spin-liquid candidate α-RuCl 3. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:475604. [PMID: 30398159 DOI: 10.1088/1361-648x/aae805] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We report detailed optical experiments on the layered compound α-RuCl3 focusing on the THz and sub-gap optical response across the structural phase transition from the monoclinic high-temperature to the rhombohedral low-temperature structure, where the stacking sequence of the molecular layers is changed. This type of phase transition is characteristic for a variety of tri-halides crystallizing in a layered honeycomb-type structure and so far is unique, as the low-temperature phase exhibits the higher symmetry. One motivation is to unravel the microscopic nature of THz and spin-orbital excitations via a study of temperature and symmetry-induced changes. The optical studies are complemented by thermal expansion experiments. We document a number of highly unusual findings: A characteristic two-step hysteresis of the structural phase transition, accompanied by a dramatic change of the reflectivity. A complex dielectric loss spectrum in the THz regime, which could indicate remnants of Kitaev physics. Orbital excitations, which cannot be explained based on recent models, and an electronic excitation, which appears in a narrow temperature range just across the structural phase transition. Despite significant symmetry changes across the monoclinic to rhombohedral phase transition and a change of the stacking sequence, phonon eigenfrequencies and the majority of spin-orbital excitations are not strongly influenced. Obviously, the symmetry of a single molecular layer determines the eigenfrequencies of most of these excitations. Only one mode at THz frequencies, which becomes suppressed in the high-temperature monoclinic phase and one phonon mode experience changes in symmetry and stacking. Finally, from this combined terahertz, far- and mid-infrared study we try to shed some light on the so far unsolved low energy (<1 eV) electronic structure of the ruthenium 4d 5 electrons in α-RuCl3.
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Affiliation(s)
- Stephan Reschke
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
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16
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Volkova LM, Marinin DV. Antiferromagnetic spin-frustrated layers of corner-sharing Cu 4 tetrahedra on the kagome lattice in volcanic minerals Cu 5O 2(VO 4) 2(CuCl), NaCu 5O 2(SeO 3) 2Cl 3, and K 2Cu 5Cl 8(OH) 4·2H 2O. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:425801. [PMID: 30166500 DOI: 10.1088/1361-648x/aade0b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The objective of the present work was to analyze the possibility of realization of quantum spin liquids in three volcanic minerals-averievite (Cu5O2(VO4)2(CuCl)), ilinskite (NaCu5O2(SeO3)2Cl3), and avdononite (K2Cu5Cl8(OH)4·2H2O)-from the crystal chemistry point of view. Based on the structural data, the sign and strength of magnetic interactions have been calculated and the geometric frustrations serving as the main reason of the existence of spin liquids have been investigated. According to our calculations, the magnetic structures of averievite and ilinskite are composed of antiferromagnetic (AFM) spin-frustrated layers of corner-sharing Cu4 tetrahedra on the kagome lattice. However, the direction of nonshared corners of tetrahedra is different in them. The oxygen ions centering the OCu4 tetrahedra in averievite and ilinskite provide the main contribution to the formation of AFM interactions along the tetrahedra edges. The local electric polarization in averievite and the possibility of spin configuration fluctuations due to vibrations of tetrahedra-centering oxygen ions have been discussed. The existence of structural phase transitions accompanied with magnetic transitions was assumed in ilinskite because of the effect of a lone electron pair by Se4+ ions. As was demonstrated through comparison of averievite and avdoninite, at the removal of centering oxygen ions from tetrahedra, the magnetic structure of the pyrochlore layer present in averievite transformed into an openwork curled net with large cells woven from corner-sharing open AFM spin-frustrated tetrahedra ('butterflies') in avdoninite.
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Affiliation(s)
- L M Volkova
- Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, 690022 Vladivostok, Russia
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17
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Abstract
A Verwey-type charge-ordering transition in magnetite at 120 K leads to the formation of linear units of three iron ions with one shared electron, called trimerons. The recently-discovered iron pentoxide (Fe4O5) comprising mixed-valent iron cations at octahedral chains, demonstrates another unusual charge-ordering transition at 150 K involving competing formation of iron trimerons and dimerons. Here, we experimentally show that applied pressure can tune the charge-ordering pattern in Fe4O5 and strongly affect the ordering temperature. We report two charge-ordered phases, the first of which may comprise both dimeron and trimeron units, whereas, the second exhibits an overall dimerization involving both the octahedral and trigonal-prismatic chains of iron in the crystal structure. We link the dramatic change in the charge-ordering pattern in the second phase to redistribution of electrons between the octahedral and prismatic iron chains, and propose that the average oxidation state of the iron cations can pre-determine a charge-ordering pattern. The charge order transition of commonly known magnetite has only recently been unraveled. Here, the measurement of the low-temperature high-pressure phase diagram of a related material (Fe4O5) elucidates the interplay of average oxidation state and charge-ordering phenomena in the iron oxide family.
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18
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Mashhadi S, Weber D, Schoop LM, Schulz A, Lotsch BV, Burghard M, Kern K. Electrical Transport Signature of the Magnetic Fluctuation-Structure Relation in α-RuCl 3 Nanoflakes. NANO LETTERS 2018; 18:3203-3208. [PMID: 29635914 DOI: 10.1021/acs.nanolett.8b00926] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The small gap semiconductor α-RuCl3 has emerged as a promising candidate for quantum spin liquid materials. Thus far, Raman spectroscopy, neutron scattering, and magnetization measurements have provided valuable hints for collective spin behavior in α-RuCl3 bulk crystals. However, the goal of implementing α-RuCl3 into spintronic devices would strongly benefit from the possibility of electrically probing these phenomena. To address this, we first investigated nanoflakes of α-RuCl3 by Raman spectroscopy and observed similar behavior as in the case of the bulk material, including the signatures of possible fractionalized excitations. In complementary experiments, we investigated the electrical charge transport properties of individual α-RuCl3 nanoflakes in the temperature range between 120 and 290 K. The observed temperature-dependent electrical resistivity is consistent with variable range hopping behavior and exhibits a transition at about 180 K, close to the onset temperature observed in our Raman measurements. In conjunction with the established relation between structure and magnetism in the bulk, we interpret this transition to coincide with the emergence of fractionalized excitations due to the Kitaev interactions in the nanoflakes. Compared to the bulk samples, the transition temperature of the underlying structural change is larger in the nanoflakes. This difference is tentatively attributed to the dimensionality of the nanoflakes as well as the formation of stacking faults during mechanical exfoliation. The demonstrated devices open up novel perspectives toward manipulating the Kitaev-phase in α-RuCl3 via electrical means.
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Affiliation(s)
- Soudabeh Mashhadi
- Max Planck Institute for Solid State Research , Heisenbergstrasse 1 , D-70569 Stuttgart , Germany
| | - Daniel Weber
- Max Planck Institute for Solid State Research , Heisenbergstrasse 1 , D-70569 Stuttgart , Germany
| | - Leslie M Schoop
- Max Planck Institute for Solid State Research , Heisenbergstrasse 1 , D-70569 Stuttgart , Germany
| | - Armin Schulz
- Max Planck Institute for Solid State Research , Heisenbergstrasse 1 , D-70569 Stuttgart , Germany
| | - Bettina V Lotsch
- Max Planck Institute for Solid State Research , Heisenbergstrasse 1 , D-70569 Stuttgart , Germany
| | - Marko Burghard
- Max Planck Institute for Solid State Research , Heisenbergstrasse 1 , D-70569 Stuttgart , Germany
| | - Klaus Kern
- Max Planck Institute for Solid State Research , Heisenbergstrasse 1 , D-70569 Stuttgart , Germany
- Institut de Physique , Ecole Polytechnique Fédérale de Lausanne , CH-1015 Lausanne , Switzerland
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19
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Agrapidis CE, van den Brink J, Nishimoto S. Ordered states in the Kitaev-Heisenberg model: From 1D chains to 2D honeycomb. Sci Rep 2018; 8:1815. [PMID: 29379081 PMCID: PMC5789058 DOI: 10.1038/s41598-018-19960-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 01/02/2018] [Indexed: 11/09/2022] Open
Abstract
We study the ground state of the 1D Kitaev-Heisenberg (KH) model using the density-matrix renormalization group and Lanczos exact diagonalization methods. We obtain a rich ground-state phase diagram as a function of the ratio between Heisenberg (J = cosϕ) and Kitaev (K = sinϕ) interactions. Depending on the ratio, the system exhibits four long-range ordered states: ferromagnetic-z, ferromagnetic-xy, staggered-xy, Néel-z, and two liquid states: Tomonaga-Luttinger liquid and spiral-xy. The two Kitaev points [Formula: see text] and [Formula: see text] are singular. The ϕ-dependent phase diagram is similar to that for the 2D honeycomb-lattice KH model. Remarkably, all the ordered states of the honeycomb-lattice KH model can be interpreted in terms of the coupled KH chains. We also discuss the magnetic structure of the K-intercalated RuCl3, a potential Kitaev material, in the framework of the 1D KH model. Furthermore, we demonstrate that the low-lying excitations of the 1D KH Hamiltonian can be explained within the combination of the known six-vertex model and spin-wave theory.
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Affiliation(s)
| | - Jeroen van den Brink
- Institute for Theoretical Solid State Physics, IFW Dresden, Dresden, 01069, Germany
- Department of Physics, Technical University Dresden, Dresden, 01069, Germany
| | - Satoshi Nishimoto
- Institute for Theoretical Solid State Physics, IFW Dresden, Dresden, 01069, Germany
- Department of Physics, Technical University Dresden, Dresden, 01069, Germany
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20
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Sarikurt S, Kadioglu Y, Ersan F, Vatansever E, Aktürk OÜ, Yüksel Y, Akıncı Ü, Aktürk E. Electronic and magnetic properties of monolayer α-RuCl3: a first-principles and Monte Carlo study. Phys Chem Chem Phys 2018; 20:997-1004. [DOI: 10.1039/c7cp07953b] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Recent experiments revealed that monolayer α-RuCl3 can be obtained by a chemical exfoliation method and exfoliation or restacking of nanosheets can manipulate the magnetic properties of the materials. Thermal variations of magnetization and specific heat curves indicate that monolayer α-RuCl3 exhibits a phase transition between ordered and disordered phases at the Curie temperature of 14.21 K.
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Affiliation(s)
- S. Sarikurt
- Dokuz Eylül University, Faculty of Science, Physics Department, Tnaztepe Campus
- 35390 Izmir
- Turkey
| | - Y. Kadioglu
- Department of Physics
- Adnan Menderes University
- Aydn 09010
- Turkey
| | - F. Ersan
- Department of Physics
- Adnan Menderes University
- Aydn 09010
- Turkey
| | - E. Vatansever
- Dokuz Eylül University, Faculty of Science, Physics Department, Tnaztepe Campus
- 35390 Izmir
- Turkey
| | - O. Üzengi Aktürk
- Department of Electrical and Electronic Engineering
- Adnan Menderes University
- 09100 Aydn
- Turkey
- Nanotechnology Application and Research Center
| | - Y. Yüksel
- Dokuz Eylül University, Faculty of Science, Physics Department, Tnaztepe Campus
- 35390 Izmir
- Turkey
| | - Ü. Akıncı
- Dokuz Eylül University, Faculty of Science, Physics Department, Tnaztepe Campus
- 35390 Izmir
- Turkey
| | - E. Aktürk
- Department of Physics
- Adnan Menderes University
- Aydn 09010
- Turkey
- Nanotechnology Application and Research Center
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21
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Winter SM, Tsirlin AA, Daghofer M, van den Brink J, Singh Y, Gegenwart P, Valentí R. Models and materials for generalized Kitaev magnetism. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:493002. [PMID: 28914608 DOI: 10.1088/1361-648x/aa8cf5] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
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 Jackeli and 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 (Na2IrO3, α-Li2IrO3, and α-RuCl3), three-dimensional Kitaev materials (β- and γ-Li2IrO3), and other potential candidates, completing the review with the list of open questions awaiting new insights.
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Affiliation(s)
- Stephen M Winter
- Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Str. 1, 60438 Frankfurt am Main, Germany
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22
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Little A, Wu L, Lampen-Kelley P, Banerjee A, Patankar S, Rees D, Bridges CA, Yan JQ, Mandrus D, Nagler SE, Orenstein J. Antiferromagnetic Resonance and Terahertz Continuum in α-RuCl_{3}. PHYSICAL REVIEW LETTERS 2017; 119:227201. [PMID: 29286790 DOI: 10.1103/physrevlett.119.227201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Indexed: 06/07/2023]
Abstract
We report measurements of optical absorption in the zigzag antiferromagnet α-RuCl_{3} as a function of temperature T, magnetic field B, and photon energy ℏω in the range ∼0.3-8.3 meV, using time-domain terahertz spectroscopy. Polarized measurements show that threefold rotational symmetry is broken in the honeycomb plane from 2 to 300 K. We find a sharp absorption peak at 2.56 meV upon cooling below the Néel temperature of 7 K at B=0 that we identify as the magnetic-dipole excitation of a zero-wave-vector magnon, or antiferromagnetic resonance (AFMR). With the application of B, the AFMR broadens and shifts to a lower frequency as long-range magnetic order is lost in a manner consistent with transitioning to a spin-disordered phase. From a direct, internally calibrated measurement of the AFMR spectral weight, we place an upper bound on the contribution to the dc susceptibility from a magnetic excitation continuum.
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Affiliation(s)
- A Little
- Department of Physics, University of California, Berkeley, California 94720, USA
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Liang Wu
- Department of Physics, University of California, Berkeley, California 94720, USA
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - P Lampen-Kelley
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - A Banerjee
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - S Patankar
- Department of Physics, University of California, Berkeley, California 94720, USA
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - D Rees
- Department of Physics, University of California, Berkeley, California 94720, USA
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - C A Bridges
- Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - J-Q Yan
- Material Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge,Tennessee 37830, USA
| | - D Mandrus
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - S E Nagler
- Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
- Bredesen Center, University of Tennessee, Knoxville, Tennessee 37966, USA
| | - J Orenstein
- Department of Physics, University of California, Berkeley, California 94720, USA
- Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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