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Zhao X, Miao X. Surface-supported metal-organic frameworks with geometric topological diversity via scanning tunneling microscopy. iScience 2024; 27:109392. [PMID: 38500826 PMCID: PMC10946334 DOI: 10.1016/j.isci.2024.109392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/20/2024] Open
Abstract
Surface-supported metal-organic frameworks (SMOFs) are long-range ordered periodic 2D lattice layers formed by inorganic metal nodes and organic ligands via coordination bonds on substrate surfaces. The atomic resolution STM lays a solid foundation for the conception and construction of SMOFs with large area, stable structure, and special function. In this review, the cutting-edge research of SMOFs from design strategy, preparation process, and how to accurately achieve structural and functional diversity are reviewed. Furthermore, we focus on the design and construction of novel and fascinating periodic and fractal structures, in which some typical honeycomb structures, Kagome lattice, hexagonal geometry, and Sierpiński triangles are summarized, and the related prospects for designing functional nanoscale systems and architectures are prospected. Finally, the challenges faced in the design and synthesis of SMOFs are denoted, and the application prospect and development trend of SMOFs are forecasted based on the current research status.
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Affiliation(s)
- Xiaoyang Zhao
- College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, People’s Republic of China
| | - Xinrui Miao
- College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, People’s Republic of China
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2
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Ko EK, Hahn S, Sohn C, Lee S, Lee SSB, Sohn B, Kim JR, Son J, Song J, Kim Y, Kim D, Kim M, Kim CH, Kim C, Noh TW. Tuning orbital-selective phase transitions in a two-dimensional Hund's correlated system. Nat Commun 2023; 14:3572. [PMID: 37328474 DOI: 10.1038/s41467-023-39188-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 05/30/2023] [Indexed: 06/18/2023] Open
Abstract
Hund's rule coupling (J) has attracted much attention recently for its role in the description of the novel quantum phases of multi-orbital materials. Depending on the orbital occupancy, J can lead to various intriguing phases. However, experimental confirmation of the orbital occupancy dependency has been difficult as controlling the orbital degrees of freedom normally accompanies chemical inhomogeneities. Here, we demonstrate a method to investigate the role of orbital occupancy in J related phenomena without inducing inhomogeneities. By growing SrRuO3 monolayers on various substrates with symmetry-preserving interlayers, we gradually tune the crystal field splitting and thus the orbital degeneracy of the Ru t2g orbitals. It effectively varies the orbital occupancies of two-dimensional (2D) ruthenates. Via in-situ angle-resolved photoemission spectroscopy, we observe a progressive metal-insulator transition (MIT). It is found that the MIT occurs with orbital differentiation: concurrent opening of a band insulating gap in the dxy band and a Mott gap in the dxz/yz bands. Our study provides an effective experimental method for investigation of orbital-selective phenomena in multi-orbital materials.
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Affiliation(s)
- Eun Kyo Ko
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
| | - Sungsoo Hahn
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
- Research Institute of Basic Sciences (RIBS), Seoul National University, Seoul, 08826, Republic of Korea
| | - Changhee Sohn
- Department of Physics, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea
| | - Sangmin Lee
- Department of Materials Science and Engineering and Research Institute of Advanced Materials, Seoul National University, Seoul, 08826, Republic of Korea
| | - Seung-Sup B Lee
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
- Center for Theoretical Physics, Seoul National University, Seoul, 08826, Republic of Korea
| | - Byungmin Sohn
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
| | - Jeong Rae Kim
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
| | - Jaeseok Son
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
| | - Jeongkeun Song
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
| | - Youngdo Kim
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
| | - Donghan Kim
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea
| | - Miyoung Kim
- Department of Materials Science and Engineering and Research Institute of Advanced Materials, Seoul National University, Seoul, 08826, Republic of Korea
| | - Choong H Kim
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea.
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea.
| | - Changyoung Kim
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea.
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea.
| | - Tae Won Noh
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, 08826, Republic of Korea.
- Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea.
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3
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Schneider L, Beck P, Rózsa L, Posske T, Wiebe J, Wiesendanger R. Probing the topologically trivial nature of end states in antiferromagnetic atomic chains on superconductors. Nat Commun 2023; 14:2742. [PMID: 37173332 PMCID: PMC10182033 DOI: 10.1038/s41467-023-38369-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Accepted: 04/25/2023] [Indexed: 05/15/2023] Open
Abstract
Spin chains proximitized by s-wave superconductors are predicted to enter a mini-gapped phase with topologically protected Majorana modes (MMs) localized at their ends. However, the presence of non-topological end states mimicking MM properties can hinder their unambiguous observation. Here, we report on a direct method to exclude the non-local nature of end states via scanning tunneling spectroscopy by introducing a locally perturbing defect on one of the chain's ends. We apply this method to particular end states observed in antiferromagnetic spin chains within a large minigap, thereby proving their topologically trivial character. A minimal model shows that, while wide trivial minigaps hosting end states are easily achieved in antiferromagnetic spin chains, unrealistically large spin-orbit coupling is required to drive the system into a topologically gapped phase with MMs. The methodology of perturbing candidate topological edge modes in future experiments is a powerful tool to probe their stability against local disorder.
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Affiliation(s)
- Lucas Schneider
- Department of Physics, University of Hamburg, D-20355, Hamburg, Germany
| | - Philip Beck
- Department of Physics, University of Hamburg, D-20355, Hamburg, Germany
| | - Levente Rózsa
- Department of Physics, University of Konstanz, D-78457, Konstanz, Germany
- Department of Theoretical Solid State Physics, Institute of Solid State Physics and Optics, Wigner Research Centre for Physics, H-1525, Budapest, Hungary
- Department of Theoretical Physics, Budapest University of Technology and Economics, H-1111, Budapest, Hungary
| | - Thore Posske
- I. Institute for Theoretical Physics, University of Hamburg, D-22607, Hamburg, Germany
- Centre for Ultrafast Imaging, Luruper Chaussee 149, D-22761, Hamburg, Germany
| | - Jens Wiebe
- Department of Physics, University of Hamburg, D-20355, Hamburg, Germany.
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4
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Gao Y, Vlaic S, Gorni T, De' Medici L, Clair S, Roditchev D, Pons S. Manipulation of the Magnetic State of a Porphyrin-Based Molecule on Gold: From Kondo to Quantum Nanomagnet via the Charge Fluctuation Regime. ACS NANO 2023; 17:9082-9089. [PMID: 37162317 DOI: 10.1021/acsnano.2c12223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
By moving individual Fe-porphyrin-based molecules with the tip of a scanning tunneling microscope in the vicinity of the elbow of the herringbone-reconstructed Au(111) containing a Br atom, we reversibly and continuously control their magnetic state. Several regimes are obtained experimentally and explored theoretically: from the integer spin limit, through intermediate magnetic states with renormalized magnetic anisotropy, until the Kondo-screened regime, corresponding to a progressive increase of charge fluctuations and mixed valency due to an increase in the interaction of the molecular Fe states with the substrate Fermi sea. Our study demonstrates the potential of utilizing charge fluctuations to generate and tune quantum magnetic states in molecule-surface hybrids.
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Affiliation(s)
- Yingzheng Gao
- Laboratoire de Physique et d'Étude des Matériaux (LPEM), ESPCI Paris, PSL Research University, CNRS UMR8213, Sorbonne Université, 75005 Paris, France
| | - Sergio Vlaic
- Laboratoire de Physique et d'Étude des Matériaux (LPEM), ESPCI Paris, PSL Research University, CNRS UMR8213, Sorbonne Université, 75005 Paris, France
| | - Tommaso Gorni
- Laboratoire de Physique et d'Étude des Matériaux (LPEM), ESPCI Paris, PSL Research University, CNRS UMR8213, Sorbonne Université, 75005 Paris, France
| | - Luca De' Medici
- Laboratoire de Physique et d'Étude des Matériaux (LPEM), ESPCI Paris, PSL Research University, CNRS UMR8213, Sorbonne Université, 75005 Paris, France
| | - Sylvain Clair
- Aix Marseille University, CNRS, IM2NP, 13397 Marseille, France
| | - Dimitri Roditchev
- Laboratoire de Physique et d'Étude des Matériaux (LPEM), ESPCI Paris, PSL Research University, CNRS UMR8213, Sorbonne Université, 75005 Paris, France
- Institut des Nanosciences de Paris, Sorbonne Université, CNRS UMR7588, 75005 Paris, France
| | - Stéphane Pons
- Laboratoire de Physique et d'Étude des Matériaux (LPEM), ESPCI Paris, PSL Research University, CNRS UMR8213, Sorbonne Université, 75005 Paris, France
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5
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Wang Y, Li X. Unravelling the robustness of magnetic anisotropy of a nickelocene molecule in different environments: a first-principles-based study. Phys Chem Chem Phys 2022; 24:21122-21130. [PMID: 36039704 DOI: 10.1039/d2cp02793c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Recent scanning tunneling spectroscopy with single metallocene molecule-functionalized tips have proved to be a powerful tool to probe and control individual spins and spin-spin exchange interactions due to the robustness of the magnetic properties of the metallocene molecule in different surroundings. However, accurate prediction of such robustness at a first-principles-based level by the conventional density functional theory (DFT) has remained challenging. In this paper, we have performed a detailed investigation of the evolution of electronic and magnetic properties of a nickelocene molecule (NiCp2) in different environments, i.e., free-standing, adsorbed on Cu(100) and as a functionalized tip apex. Using an embedding method, which combines DFT and the complete active space self-consistent field (CASSCF) method recently developed, we demonstrate that the nickelocene molecule almost preserves its spin and magnetic anisotropy upon adsorption on Cu(100), and also in the position of the tip apex. In particular, the cyclic π* orbital of the Cp rings could hybridize with the singly occupied dπ orbitals of the Ni center of the molecule, protecting these orbitals from external states. Hence the molecular spin maintains S = 1, the same as in the free-standing case, and its magnetic anisotropy is also robust with energies of 3.56, 3.34, and 3.51 meV in free-standing, adsorbed on Cu(100), and functionalized tip apex states, respectively, in good agreement with previous theoretical and experimental results. This work thus provides a first-principles-based understanding of the relevant experiments. Such agreement between theoretical simulations and experimental measurements highlights the potential usefulness of the method for investigating the local electronic and spin states of organometallic molecule-surface composite systems.
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Affiliation(s)
- Yu Wang
- Institute for Advanced Study, Shenzhen University, Shenzhen 518060, China.
| | - Xiaoguang Li
- Institute for Advanced Study, Shenzhen University, Shenzhen 518060, China.
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6
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Magnetic control over the fundamental structure of atomic wires. Nat Commun 2022; 13:4113. [PMID: 35840588 PMCID: PMC9287401 DOI: 10.1038/s41467-022-31456-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Accepted: 06/17/2022] [Indexed: 11/30/2022] Open
Abstract
When reducing the size of materials towards the nanoscale, magnetic properties can emerge due to structural variations. Here, we show the reverse effect, where the structure of nanomaterials is controlled by magnetic manipulations. Using the break-junction technique, we find that the interatomic distance in platinum atomic wires is shorter or longer by up to ∼20%, when a magnetic field is applied parallel or perpendicular to the wires during their formation, respectively. The magnetic field direction also affects the wire length, where longer (shorter) wires are formed under a parallel (perpendicular) field. Our experimental analysis, supported by calculations, indicates that the direction of the applied magnetic field promotes the formation of suspended atomic wires with a specific magnetization orientation associated with typical orbital characteristics, interatomic distance, and stability. A similar effect is found for various metal and metal-oxide atomic wires, demonstrating that magnetic fields can control the atomistic structure of different nanomaterials when applied during their formation stage. Magnetic effects can emerge due to structural variations when the size of materials is reduced towards the nanoscale. Here, Chakrabarti et al demonstrates the opposite effect, showing that the interatomic distance in atomic wires changes by up to 20% depending on the orientation of an applied magnetic field.
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7
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Li S, Czap G, Li J, Zhang Y, Yu A, Yuan D, Kimura H, Wu R, Ho W. Confinement-Induced Catalytic Dissociation of Hydrogen Molecules in a Scanning Tunneling Microscope. J Am Chem Soc 2022; 144:9618-9623. [PMID: 35486711 DOI: 10.1021/jacs.2c00005] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The catalytic scission of single chemical bonds has been induced by the nanoscale confinement in a scanning tunneling microscope (STM) junction. Individual hydrogen molecules sandwiched between the STM tip and a copper substrate can be dissociated solely by the reciprocating movement of the tip. The reaction rate depends sensitively on the local molecular environment, as exemplified by the effects of a nearby carbon monoxide molecule or a gold adatom. Detailed mechanisms and the nature of the transition states are revealed by density functional theory (DFT) calculations. This work provides insights into chemical reactions at the atomic scale induced by localized confinement applied by the STM tip. Furthermore, a single diatomic molecule can act as a molecular catalyst to enhance the reaction rate on a surface.
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Affiliation(s)
- Shaowei Li
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, United States
| | - Gregory Czap
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, United States
| | - Jie Li
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, United States
| | - Yanxing Zhang
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, United States.,College of Physics and Electrical Engineering, Henan Normal University, Xinxiang, Henan 453007, China
| | - Arthur Yu
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, United States
| | - Dingwang Yuan
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, United States.,College of Materials Science and Engineering, Hunan University, Changsha, Hunan 410082, China
| | - Hikari Kimura
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, United States
| | - Ruqian Wu
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, United States
| | - W Ho
- Department of Physics and Astronomy, University of California, Irvine, California 92697-4575, United States.,Department of Chemistry, University of California, Irvine, California 92697-2025, United States
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8
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Ruiz-Díaz P, Núñez-Valencia C, Muñoz-Navia M, Urrutia-Bañuelos E, Dorantes-Dávila J. Tuning the magnetic anisotropy energy by external electric fields of CoPt dimers deposited on graphene. Phys Chem Chem Phys 2022; 24:9576-9588. [PMID: 35403183 DOI: 10.1039/d2cp00482h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In the framework of first-principles calculations, we comprehensively investigate the external electric-field (EF) manipulation of the magnetic anisotropy energy (MAE) of alloyed CoPt dimers deposited on graphene. In particular, we focus on the possibility of tuning the MAE barriers under the action of external EFs and on the effects of Co-substitution. Among the various considered structures, the lowest-energy configurations were the hollow-upright and top-upright, having the Co-atom closest to the graphene layer. The optimal and higher energy configurations were related to the electronic structure through the local density of states and hybridizations between the transition-metal (TM) atoms of the dimer and graphene. In contrast to Co2/graphene [M. Tanveer, J. Dorantes-Dávila and G. M. Pastor, Phys. Rev. B, 2017, 96(22), 224413.], the CoPt dimer having the hollow-upright ground-state configuration, exhibits a much lower value of the MAE (about |ΔE| ≃ 4.5 meV per atom) and the direction of the magnetization lies in the graphene layer. Moreover, we observe a spin-reorientation transition occurring at εz ≃ 0.5 V Å-1, which opens the possibility of inducing magnetization switching by external electric fields. The microscopic origin of the changes of the MAE associated with changes in the EF has been qualitatively related to the details of the electronic structure by analyzing the local density of states and to the spin-dependent electronic densities close to the Fermi energy. Finally, the role of local environment was quantified by performing electronic structure and magnetic calculations on several higher-energy structure configurations.
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Affiliation(s)
- P Ruiz-Díaz
- Instituto de Física, Universidad Autónoma de San Luis Potosí, 78000 San Luis Potosí, México.
| | - C Núñez-Valencia
- Instituto de Física, Universidad Autónoma de San Luis Potosí, 78000 San Luis Potosí, México.
| | - M Muñoz-Navia
- Universidad de La Ciénega del Estado de Michoacán de Ocampo, Col. Lomas de la Universidad, Avenida Universidad 3000, Sahuayo, Michoacán, México
| | - E Urrutia-Bañuelos
- Departamento de Investigación en Física, Universidad de Sonora, 78000 Sonora, México
| | - J Dorantes-Dávila
- Instituto de Física, Universidad Autónoma de San Luis Potosí, 78000 San Luis Potosí, México.
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9
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Liu B, Miao G, Zhong W, Huang X, Su N, Guo J, Wang W. Manipulating the Electronic and Magnetic Properties of Coordinated Nickel Atoms in Metal-Organic Frameworks by Hydrogenation. ACS NANO 2022; 16:2147-2153. [PMID: 35041376 DOI: 10.1021/acsnano.1c07902] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
In the pursuit of manipulating the properties of single atoms, the surface-supported metal-organic frameworks (MOFs) provide us opportunities to individually address the electronic and magnetic properties of coordinated metal atoms by scanning tunneling microscopy. Recently, we have synthesized Ni-TPyP (TPyP = 5,10,15,20-tetra-(4-pyridyl) porphyrin) networks with dinuclear Ni centers on a Au(111) surface, in which the top-Ni atoms are sitting above the molecular plane. Here, we investigate the top-Ni atoms and their hydrogenated derivatives by low-temperature scanning tunneling microscopy and spectroscopy, and show that the electronic and magnetic states of top-Ni atoms can be manipulated by hydrogen adsorption. Specifically, by fitting the spin-flip spectra in vertical magnetic field, we find the spin state of top-Ni atoms is tuned from S = 1/2 to S = 1 by attaching one H atom and S = 3/2 by attaching two H atoms. Our work demonstrates atomic-scale control over the electronic and magnetic properties of coordinated metal atoms in a surface-supported MOF.
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Affiliation(s)
- Bing Liu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Guangyao Miao
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Weiliang Zhong
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Xiaochun Huang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Nuoyu Su
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Jiandong Guo
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, China
| | - Weihua Wang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
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10
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Drechsel C, D’Astolfo P, Liu JC, Glatzel T, Pawlak R, Meyer E. Topographic signatures and manipulations of Fe atoms, CO molecules and NaCl islands on superconducting Pb(111). BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2022; 13:1-9. [PMID: 35059274 PMCID: PMC8744454 DOI: 10.3762/bjnano.13.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Accepted: 12/08/2021] [Indexed: 06/14/2023]
Abstract
Topological superconductivity emerging in one- or two-dimensional hybrid materials is predicted as a key ingredient for quantum computing. However, not only the design of complex heterostructures is primordial for future applications but also the characterization of their electronic and structural properties at the atomic scale using the most advanced scanning probe microscopy techniques with functionalized tips. We report on the topographic signatures observed by scanning tunneling microscopy (STM) of carbon monoxide (CO) molecules, iron (Fe) atoms and sodium chloride (NaCl) islands deposited on superconducting Pb(111). For the CO adsorption a comparison with the Pb(110) substrate is demonstrated. We show a general propensity of these adsorbates to diffuse at low temperature under gentle scanning conditions. Our findings provide new insights into high-resolution probe microscopy imaging with terminated tips, decoupling atoms and molecules by NaCl islands or tip-induced lateral manipulation of iron atoms on top of the prototypical Pb(111) superconducting surface.
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Affiliation(s)
- Carl Drechsel
- Department of Physics, Universität Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
| | - Philipp D’Astolfo
- Department of Physics, Universität Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
| | - Jung-Ching Liu
- Department of Physics, Universität Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
| | - Thilo Glatzel
- Department of Physics, Universität Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
| | - Rémy Pawlak
- Department of Physics, Universität Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
| | - Ernst Meyer
- Department of Physics, Universität Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
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11
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Wang Y, Li X, Yang J. Spin-flip excitations induced by dehydrogenation in a magnetic single-molecule junction. J Chem Phys 2019; 151:224704. [DOI: 10.1063/1.5129288] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Yu Wang
- Institute for Advanced Study, Shenzhen University, Shenzhen 518060, China
| | - Xiaoguang Li
- Institute for Advanced Study, Shenzhen University, Shenzhen 518060, China
| | - Jinlong Yang
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
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12
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Signatures of Mottness and Hundness in archetypal correlated metals. Nat Commun 2019; 10:2721. [PMID: 31221960 PMCID: PMC6586627 DOI: 10.1038/s41467-019-10257-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 04/26/2019] [Indexed: 02/06/2023] Open
Abstract
Physical properties of multi-orbital materials depend not only on the strength of the effective interactions among the valence electrons but also on their type. Strong correlations are caused by either Mott physics that captures the Coulomb repulsion among charges, or Hund physics that aligns the spins in different orbitals. We identify four energy scales marking the onset and the completion of screening in orbital and spin channels. The differences in these scales, which are manifest in the temperature dependence of the local spectrum and of the charge, spin and orbital susceptibilities, provide clear signatures distinguishing Mott and Hund physics. We illustrate these concepts with realistic studies of two archetypal strongly correlated materials, and corroborate the generality of our conclusions with a model Hamiltonian study.
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13
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Wang Y, Li X, Yang J. Electronic and magnetic properties of CoPc and FePc molecules on graphene: the substrate, defect, and hydrogen adsorption effects. Phys Chem Chem Phys 2019; 21:5424-5434. [PMID: 30793133 DOI: 10.1039/c8cp07091a] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Transition metal phthalocyanines (TMPcs) are particularly appealing for spintronic processing and data storage devices due to their structural simplicity and functional flexibility. To realize effective control of the spins in TMPc-based systems, it is necessary to quantify how the structural and chemical environment of the molecule affects its spin center. Herein we perform a detailed investigation of the electronic and spintronic properties of vertically stacked heterostructures formed by CoPc or FePc adsorbed on a monolayer of graphene under the influences of the gold substrate, vacancies in graphene, and extra atomic hydrogen coordination on the TMPc. By using density functional theory (DFT), we reveal that both the TMPc molecules prefer the carbon-top position on graphene, and the existence of the Au substrate enhances the stability of the adsorption, while this enhanced adsorption will not modify the molecular magnetism, keeping it the same value as in the free standing case. Moreover, with the aid of a combination of DFT and ab initio wavefunction-based calculations, our results indicate that the magnetic anisotropy of the FePc-graphene complex can be actively tuned by the Au substrate. Our calculations also show that defects in graphene including single and double vacancies can modify the magnetism of these heterostructures. In particular, the spin state of FePc can be tuned from S = 1 to S = 2 with such defect engineering. Further spin state tunability can be achieved from a hydrogenation process, with the coordination of one extra hydrogen on the Co-top site for CoPc and the pyridinic N site for FePc, respectively, tuning their spin states from S = 1/2 to S = 0 and from S = 1 to S = 2. These findings may prove to be instrumental for rational design of future molecular spintronics devices integrated with two-dimensional materials.
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Affiliation(s)
- Yu Wang
- Institute for Advanced Study, Shenzhen University, Shenzhen 518060, China.
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14
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Tomczak JM. Thermoelectricity in correlated narrow-gap semiconductors. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:183001. [PMID: 29633717 DOI: 10.1088/1361-648x/aab284] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We review many-body effects, their microscopic origin, as well as their impact on thermoelectricity in correlated narrow-gap semiconductors. Members of this class-such as FeSi and FeSb2-display an unusual temperature dependence in various observables: insulating with large thermopowers at low temperatures, they turn bad metals at temperatures much smaller than the size of their gaps. This insulator-to-metal crossover is accompanied by spectral weight-transfers over large energies in the optical conductivity and by a gradual transition from activated to Curie-Weiss-like behaviour in the magnetic susceptibility. We show a retrospective of the understanding of these phenomena, discuss the relation to heavy-fermion Kondo insulators-such as Ce3Bi4Pt3 for which we present new results-and propose a general classification of paramagnetic insulators. From the latter, FeSi emerges as an orbital-selective Kondo insulator. Focussing on intermetallics such as silicides, antimonides, skutterudites, and Heusler compounds we showcase successes and challenges for the realistic simulation of transport properties in the presence of electronic correlations. Further, we explore new avenues in which electronic correlations may contribute to the improvement of thermoelectric performance.
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Affiliation(s)
- Jan M Tomczak
- Institute of Solid State Physics, TU Wien, A-1040 Vienna, Austria
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15
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Hsu PJ, Rózsa L, Finco A, Schmidt L, Palotás K, Vedmedenko E, Udvardi L, Szunyogh L, Kubetzka A, von Bergmann K, Wiesendanger R. Inducing skyrmions in ultrathin Fe films by hydrogen exposure. Nat Commun 2018; 9:1571. [PMID: 29679007 PMCID: PMC5910423 DOI: 10.1038/s41467-018-04015-z] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 03/27/2018] [Indexed: 11/16/2022] Open
Abstract
Magnetic skyrmions are localized nanometer-sized spin configurations with particle-like properties, which are envisioned to be used as bits in next-generation information technology. An essential step toward future skyrmion-based applications is to engineer key magnetic parameters for developing and stabilizing individual magnetic skyrmions. Here we demonstrate the tuning of the non-collinear magnetic state of an Fe double layer on an Ir(111) substrate by loading the sample with atomic hydrogen. By using spin-polarized scanning tunneling microscopy, we discover that the hydrogenated system supports the formation of skyrmions in external magnetic fields, while the pristine Fe double layer does not. Based on ab initio calculations, we attribute this effect to the tuning of the Heisenberg exchange and the Dzyaloshinsky–Moriya interactions due to hydrogenation. In addition to interface engineering, hydrogenation of thin magnetic films offers a unique pathway to design and optimize the skyrmionic states in low-dimensional magnetic materials. Stabilization of skyrmions is one of the key issues in skyrmion-based spintronics. Here the authors demonstrate that hydrogenation can induce the formation of skyrmions in iron thin films, which provides an alternative way to tailor skyrmion states in low-dimensional magnetic materials.
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Affiliation(s)
- Pin-Jui Hsu
- Department of Physics, University of Hamburg, 20355, Hamburg, Germany. .,Department of Physics, National Tsing Hua University, 30013, Hsinchu, Taiwan.
| | - Levente Rózsa
- Department of Physics, University of Hamburg, 20355, Hamburg, Germany. .,Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Budapest, 1525, Hungary.
| | - Aurore Finco
- Department of Physics, University of Hamburg, 20355, Hamburg, Germany
| | - Lorenz Schmidt
- Department of Physics, University of Hamburg, 20355, Hamburg, Germany
| | - Krisztián Palotás
- Institute of Physics, Slovak Academy of Sciences, 84511, Bratislava, Slovakia.,MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, University of Szeged, Szeged, 6720, Hungary
| | - Elena Vedmedenko
- Department of Physics, University of Hamburg, 20355, Hamburg, Germany
| | - László Udvardi
- Department of Theoretical Physics, Budapest University of Technology and Economics, Budapest, 1111, Hungary.,MTA-BME Condensed Matter Research Group, Budapest University of Technology and Economics, Budapest, 1111, Hungary
| | - László Szunyogh
- Department of Theoretical Physics, Budapest University of Technology and Economics, Budapest, 1111, Hungary.,MTA-BME Condensed Matter Research Group, Budapest University of Technology and Economics, Budapest, 1111, Hungary
| | - André Kubetzka
- Department of Physics, University of Hamburg, 20355, Hamburg, Germany
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16
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Zhang KC, Li YF, Liu Y, Zhu Y. Giant magnetic anisotropy and robust quantum anomalous Hall effect in boron-doped graphene with Re-adsorption. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:145001. [PMID: 29465040 DOI: 10.1088/1361-648x/aab111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Recently topological materials have attracted much attention due to their quantization transports as well as edge states. It will be excellent to realize the robust quantum anomalous Hall transports in graphene-based devices. Using density-functional theory and tight-binding method, we investigated the structural, magnetic and topological properties for the boron-doped graphene with Re-adsorption. A large band-gap of 32.5 meV is opened by the Rashba spin-orbital coupling, and the band-gap is robust against the shape deformation of ±[Formula: see text] along the zigzag direction. Giant magnetic anisotropy emerges in this adsorption system together with the Fermi level lying in the band gap. Both the magnetic anisotropy and the band gap can be tuned by a moderate electric field. Calculations reveal that the system exhibits the quantization transports with the Chern number [Formula: see text].
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Affiliation(s)
- Kai-Cheng Zhang
- College of Mathematics and Physics, Bohai University, Jinzhou 121013, People's Republic of China
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17
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Hermenau J, Ternes M, Steinbrecher M, Wiesendanger R, Wiebe J. Long Spin-Relaxation Times in a Transition-Metal Atom in Direct Contact to a Metal Substrate. NANO LETTERS 2018; 18:1978-1983. [PMID: 29466854 DOI: 10.1021/acs.nanolett.7b05392] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Long spin-relaxation times are a prerequisite for the use of spins in data storage or nanospintronics technologies. An atomic-scale solid-state realization of such a system is the spin of a transition-metal atom adsorbed on a suitable substrate. For the case of a metallic substrate, which enables the direct addressing of the spin by conduction electrons, the experimentally measured lifetimes reported to date are on the order of only hundreds of femtoseconds. Here, we show that the spin states of iron atoms adsorbed directly on a conductive platinum substrate have a surprisingly long spin-relaxation time in the nanosecond regime, which is comparable to that of a transition metal atom decoupled from the substrate electrons by a thin decoupling layer. The combination of long spin-relaxation times and strong coupling to conduction electrons implies the possibility to use flexible coupling schemes to process the spin information.
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Affiliation(s)
- Jan Hermenau
- Department of Physics , Hamburg University , Jungiusstrasse 11 , D-20355 Hamburg , Germany
| | - Markus Ternes
- Max-Planck Institute for Solid State Research , Heisenbergstrasse 1 , D-70569 Stuttgart , Germany
| | - Manuel Steinbrecher
- Department of Physics , Hamburg University , Jungiusstrasse 11 , D-20355 Hamburg , Germany
| | - Roland Wiesendanger
- Department of Physics , Hamburg University , Jungiusstrasse 11 , D-20355 Hamburg , Germany
| | - Jens Wiebe
- Department of Physics , Hamburg University , Jungiusstrasse 11 , D-20355 Hamburg , Germany
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18
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von Allwörden H, Eich A, Knol EJ, Hermenau J, Sonntag A, Gerritsen JW, Wegner D, Khajetoorians AA. Design and performance of an ultra-high vacuum spin-polarized scanning tunneling microscope operating at 30 mK and in a vector magnetic field. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2018; 89:033902. [PMID: 29604794 DOI: 10.1063/1.5020045] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We describe the design and performance of a scanning tunneling microscope (STM) that operates at a base temperature of 30 mK in a vector magnetic field. The cryogenics is based on an ultra-high vacuum (UHV) top-loading wet dilution refrigerator that contains a vector magnet allowing for fields up to 9 T perpendicular and 4 T parallel to the sample. The STM is placed in a multi-chamber UHV system, which allows in situ preparation and exchange of samples and tips. The entire system rests on a 150-ton concrete block suspended by pneumatic isolators, which is housed in an acoustically isolated and electromagnetically shielded laboratory optimized for extremely low noise scanning probe measurements. We demonstrate the overall performance by illustrating atomic resolution and quasiparticle interference imaging and detail the vibrational noise of both the laboratory and microscope. We also determine the electron temperature via measurement of the superconducting gap of Re(0001) and illustrate magnetic field-dependent measurements of the spin excitations of individual Fe atoms on Pt(111). Finally, we demonstrate spin resolution by imaging the magnetic structure of the Fe double layer on W(110).
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Affiliation(s)
- Henning von Allwörden
- Scanning Probe Microscopy Department, Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | - Andreas Eich
- Scanning Probe Microscopy Department, Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | - Elze J Knol
- Scanning Probe Microscopy Department, Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | - Jan Hermenau
- Department of Physics, Hamburg University, Hamburg, Germany
| | | | - Jan W Gerritsen
- Scanning Probe Microscopy Department, Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | - Daniel Wegner
- Scanning Probe Microscopy Department, Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
| | - Alexander A Khajetoorians
- Scanning Probe Microscopy Department, Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands
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19
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Wang Y, Li X, Zheng X, Yang J. Manipulation of spin and magnetic anisotropy in bilayer magnetic molecular junctions. Phys Chem Chem Phys 2018; 20:26396-26404. [DOI: 10.1039/c8cp05759a] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The Kondo effect and magnetic anisotropy in bilayer TMPc/TMPc/Pb(111) junctions can be actively tuned by changing the intermediate decoupling layer.
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Affiliation(s)
- Yu Wang
- Institute for Advanced Study
- Shenzhen University
- Shenzhen 518060
- China
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province
| | - Xiaoguang Li
- Institute for Advanced Study
- Shenzhen University
- Shenzhen 518060
- China
| | - Xiao Zheng
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics
- University of Science and Technology of China
- Hefei 230026
- China
| | - Jinlong Yang
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics
- University of Science and Technology of China
- Hefei 230026
- China
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20
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Controlled spin switching in a metallocene molecular junction. Nat Commun 2017; 8:1974. [PMID: 29215014 PMCID: PMC5719446 DOI: 10.1038/s41467-017-02151-6] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 11/09/2017] [Indexed: 12/01/2022] Open
Abstract
The active control of a molecular spin represents one of the main challenges in molecular spintronics. Up to now spin manipulation has been achieved through the modification of the molecular structure either by chemical doping or by external stimuli. However, the spin of a molecule adsorbed on a surface depends primarily on the interaction between its localized orbitals and the electronic states of the substrate. Here we change the effective spin of a single molecule by modifying the molecule/metal interface in a controlled way using a low-temperature scanning tunneling microscope. A nickelocene molecule reversibly switches from a spin 1 to 1/2 when varying the electrode–electrode distance from tunnel to contact regime. This switching is experimentally evidenced by inelastic and elastic spin-flip mechanisms observed in reproducible conductance measurements and understood using first principle calculations. Our work demonstrates the active control over the spin state of single molecule devices through interface manipulation. Manipulating spin states of molecules in a controllable manner is essential to develop the molecule-based spintronics technologies. Here, Ormaza et al. show how to use the interaction between a single metallocene molecule and a metallic surface to reversibly switch spin from 1 to ½ in a junction.
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21
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Shao B, Schüler M, Schönhoff G, Frauenheim T, Czycholl G, Wehling TO. Optically and Electrically Controllable Adatom Spin-orbital Dynamics in Transition Metal Dichalcogenides. NANO LETTERS 2017; 17:6721-6726. [PMID: 28978200 DOI: 10.1021/acs.nanolett.7b02785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We analyze the interplay of spin-valley coupling, orbital physics, and magnetic anisotropy taking place at single magnetic atoms adsorbed on semiconducting transition metal dichalcogenides, MX2 (M = Mo, W; X = S, Se). Orbital selection rules turn out to govern the kinetic exchange coupling between the adatom and charge carriers in the MX2 and lead to highly orbitally dependent spin-flip scattering rates, as we illustrate for the example of transition metal adatoms with d9 configuration. Our ab initio calculations suggest that d9 configurations are realizable by single Co, Rh, or Ir adatoms on MoS2, which additionally exhibit a sizable magnetic anisotropy. We find that the interaction of the adatom with carriers in the MX2 allows to tune its behavior from a quantum regime with full Kondo screening to a regime of "Ising spintronics" where its spin-orbital moment acts as classical bit, which can be erased and written electronically and optically.
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Affiliation(s)
- Bin Shao
- Bremen Center for Computational Materials Science and ‡Institut für Theoretische Physik, Universität Bremen , 28359 Bremen, Germany
| | - Malte Schüler
- Bremen Center for Computational Materials Science and ‡Institut für Theoretische Physik, Universität Bremen , 28359 Bremen, Germany
| | - Gunnar Schönhoff
- Bremen Center for Computational Materials Science and ‡Institut für Theoretische Physik, Universität Bremen , 28359 Bremen, Germany
| | - Thomas Frauenheim
- Bremen Center for Computational Materials Science and ‡Institut für Theoretische Physik, Universität Bremen , 28359 Bremen, Germany
| | - Gerd Czycholl
- Bremen Center for Computational Materials Science and ‡Institut für Theoretische Physik, Universität Bremen , 28359 Bremen, Germany
| | - Tim O Wehling
- Bremen Center for Computational Materials Science and ‡Institut für Theoretische Physik, Universität Bremen , 28359 Bremen, Germany
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22
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Wang Y, Li X, Zheng X, Yang J. Spin switch in iron phthalocyanine on Au(111) surface by hydrogen adsorption. J Chem Phys 2017; 147:134701. [PMID: 28987089 DOI: 10.1063/1.4996970] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The manipulation of spin states at the molecular scale is of fundamental importance for the development of molecular spintronic devices. One of the feasible approaches for the modification of a molecular spin state is through the adsorption of certain specific atoms or molecules including H, NO, CO, NH3, and O2. In this paper, we demonstrate that the local spin state of an individual iron phthalocyanine (FePc) molecule adsorbed on an Au(111) surface exhibits controllable switching by hydrogen adsorption, as evidenced by using first-principles calculations based on density functional theory. Our theoretical calculations indicate that different numbers of hydrogen adsorbed at the pyridinic N sites of the FePc molecule largely modify the structural and electronic properties of the FePc/Au(111) composite by forming extra N-H bonds. In particular, the adsorption of one or up to three hydrogen atoms induces a redistribution of charge (spin) density within the FePc molecule, and hence a switching to a low spin state (S = 1/2) from an intermediate spin state (S = 1) is achieved, while the adsorption of four hydrogen atoms distorts the molecular conformation by increasing Fe-N bond lengths in FePc and thus breaks the ligand field exerted on the Fe 3d orbitals via stronger hybridization with the substrate, leading to an opposite switching to a high-spin state (S = 2). These findings obtained from the theoretical simulations could be useful for experimental manipulation or design of single-molecule spintronic devices.
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Affiliation(s)
- Yu Wang
- Institute for Advanced Study, Shenzhen University, Shenzhen 518060, China
| | - Xiaoguang Li
- Institute for Advanced Study, Shenzhen University, Shenzhen 518060, China
| | - Xiao Zheng
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Jinlong Yang
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
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23
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Hermenau J, Ibañez-Azpiroz J, Hübner C, Sonntag A, Baxevanis B, Ton KT, Steinbrecher M, Khajetoorians AA, Dos Santos Dias M, Blügel S, Wiesendanger R, Lounis S, Wiebe J. A gateway towards non-collinear spin processing using three-atom magnets with strong substrate coupling. Nat Commun 2017; 8:642. [PMID: 28935897 PMCID: PMC5608713 DOI: 10.1038/s41467-017-00506-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 07/05/2017] [Indexed: 11/09/2022] Open
Abstract
A cluster of a few magnetic atoms on the surface of a nonmagnetic substrate is one suitable realization of a bit for spin-based information technology. The prevalent approach to achieve magnetic stability is decoupling the cluster spin from substrate conduction electrons in order to suppress destabilizing spin-flips. However, this route entails less flexibility in tailoring the coupling between the bits needed for spin-processing. Here, we use a spin-resolved scanning tunneling microscope to write, read, and store spin information for hours in clusters of three atoms strongly coupled to a substrate featuring a cloud of non-collinearly polarized host atoms, a so-called non-collinear giant moment cluster. The giant moment cluster can be driven into a Kondo screened state by simply moving one of its atoms to a different site. Using the exceptional atomic tunability of the non-collinear substrate mediated Dzyaloshinskii–Moriya interaction, we propose a logical scheme for a four-state memory. Information technology based on few atom magnets requires both long spin-energy relaxation times and flexible inter-bit coupling. Here, the authors show routes to manipulate information in three-atom clusters strongly coupled to substrate electrons by exploiting Dzyaloshinskii–Moriya interactions.
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Affiliation(s)
- J Hermenau
- Department of Physics, Hamburg University, 20355, Hamburg, Germany
| | - J Ibañez-Azpiroz
- Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich & JARA, Jülich, 52425, Germany
| | - Chr Hübner
- Department of Physics, Hamburg University, 20355, Hamburg, Germany
| | - A Sonntag
- Department of Physics, Hamburg University, 20355, Hamburg, Germany
| | - B Baxevanis
- Leiden Institute of Physics, Leiden University, 2333, CA, Leiden, The Netherlands
| | - K T Ton
- Department of Physics, Hamburg University, 20355, Hamburg, Germany
| | - M Steinbrecher
- Department of Physics, Hamburg University, 20355, Hamburg, Germany
| | - A A Khajetoorians
- Department of Physics, Hamburg University, 20355, Hamburg, Germany.,Institute for Molecules and Materials (IMM), Radboud University, 6525, AJ, Nijmegen, The Netherlands
| | - M Dos Santos Dias
- Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich & JARA, Jülich, 52425, Germany
| | - S Blügel
- Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich & JARA, Jülich, 52425, Germany
| | - R Wiesendanger
- Department of Physics, Hamburg University, 20355, Hamburg, Germany
| | - S Lounis
- Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich & JARA, Jülich, 52425, Germany
| | - J Wiebe
- Department of Physics, Hamburg University, 20355, Hamburg, Germany.
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24
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Ormaza M, Bachellier N, Faraggi MN, Verlhac B, Abufager P, Ohresser P, Joly L, Romeo M, Scheurer F, Bocquet ML, Lorente N, Limot L. Efficient Spin-Flip Excitation of a Nickelocene Molecule. NANO LETTERS 2017; 17:1877-1882. [PMID: 28199115 DOI: 10.1021/acs.nanolett.6b05204] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Inelastic electron tunneling spectroscopy (IETS) within the junction of a scanning tunneling microscope (STM) uses current-driven spin-flip excitations for an all-electrical characterization of the spin state of a single object. Usually decoupling layers between the single object, atom or molecule, and the supporting surface are needed to observe these excitations. Here we study the surface magnetism of a sandwich nickelocene molecule (Nc) adsorbed directly on Cu(100) by means of X-ray magnetic circular dichroism (XMCD) and density functional theory (DFT) calculations and show with IETS that it exhibits an exceptionally efficient spin-flip excitation. The molecule preserves its magnetic moment and magnetic anisotropy not only on Cu(100), but also in different metallic environments including the tip apex. By taking advantage of this robusteness, we are able to functionalize the microscope tip with a Nc, which can be employed as a portable source of inelastic excitations as exemplified by a double spin-flip excitation process.
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Affiliation(s)
- Maider Ormaza
- Université de Strasbourg , CNRS, IPCMS, UMR 7504, F-67000 Strasbourg, France
| | - Nicolas Bachellier
- Université de Strasbourg , CNRS, IPCMS, UMR 7504, F-67000 Strasbourg, France
| | - Marisa N Faraggi
- Département de Chimie, ENS-CNRS-UPMC UMR 8640, Ecole Normale Supérieure , 75005 Paris, France
| | - Benjamin Verlhac
- Université de Strasbourg , CNRS, IPCMS, UMR 7504, F-67000 Strasbourg, France
| | - Paula Abufager
- Instituto de Física de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Rosario , Av. Pellegrini 250, 2000 Rosario, Argentina
| | - Philippe Ohresser
- L'Orme des Merisiers, Synchrotron SOLEIL , Saint-Aubin - BP 48, 91192 Gif-sur-Yvette, France
| | - Loïc Joly
- Université de Strasbourg , CNRS, IPCMS, UMR 7504, F-67000 Strasbourg, France
| | - Michelangelo Romeo
- Université de Strasbourg , CNRS, IPCMS, UMR 7504, F-67000 Strasbourg, France
| | - Fabrice Scheurer
- Université de Strasbourg , CNRS, IPCMS, UMR 7504, F-67000 Strasbourg, France
| | - Marie-Laure Bocquet
- Département de Chimie, ENS-CNRS-UPMC UMR 8640, Ecole Normale Supérieure , 75005 Paris, France
| | - Nicolás Lorente
- Centro de Fı́sica de Materiales CFM/MPC (CSIC-UPV/EHU) , Paseo Manuel de Lardizabal 5, 20018 Donostia-San Sebastián, Spain
- Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, E-20018 Donostia-San Sebastián, Spain
| | - Laurent Limot
- Université de Strasbourg , CNRS, IPCMS, UMR 7504, F-67000 Strasbourg, France
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25
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Belabbes A, Bihlmayer G, Bechstedt F, Blügel S, Manchon A. Hund's Rule-Driven Dzyaloshinskii-Moriya Interaction at 3d-5d Interfaces. PHYSICAL REVIEW LETTERS 2016; 117:247202. [PMID: 28009218 DOI: 10.1103/physrevlett.117.247202] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Indexed: 06/06/2023]
Abstract
Using relativistic first-principles calculations, we show that the chemical trend of the Dzyaloshinskii-Moriya interaction (DMI) in 3d-5d ultrathin films follows Hund's first rule with a tendency similar to their magnetic moments in either the unsupported 3d monolayers or 3d-5d interfaces. We demonstrate that, besides the spin-orbit coupling (SOC) effect in inversion asymmetric noncollinear magnetic systems, the driving force is the 3d orbital occupations and their spin-flip mixing processes with the spin-orbit active 5d states control directly the sign and magnitude of the DMI. The magnetic chirality changes are discussed in the light of the interplay between SOC, Hund's first rule, and the crystal-field splitting of d orbitals.
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Affiliation(s)
- A Belabbes
- King Abdullah University of Science and Technology (KAUST), Physical Science and Engineering Division (PSE), Thuwal 23955-6900, Saudi Arabia
| | - G Bihlmayer
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, D-52425 Jülich, Germany
| | - F Bechstedt
- Institut für Festkörpertheorie und -optik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany
| | - S Blügel
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, D-52425 Jülich, Germany
| | - A Manchon
- King Abdullah University of Science and Technology (KAUST), Physical Science and Engineering Division (PSE), Thuwal 23955-6900, Saudi Arabia
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26
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Kondo T, Ochi M, Nakayama M, Taniguchi H, Akebi S, Kuroda K, Arita M, Sakai S, Namatame H, Taniguchi M, Maeno Y, Arita R, Shin S. Orbital-Dependent Band Narrowing Revealed in an Extremely Correlated Hund's Metal Emerging on the Topmost Layer of Sr_{2}RuO_{4}. PHYSICAL REVIEW LETTERS 2016; 117:247001. [PMID: 28009182 DOI: 10.1103/physrevlett.117.247001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2016] [Indexed: 06/06/2023]
Abstract
We use a surface-selective angle-resolved photoemission spectroscopy and unveil the electronic nature on the topmost layer of Sr_{2}RuO_{4} crystal, consisting of slightly rotated RuO_{6} octahedrons. The γ band derived from the 4d_{xy} orbital is found to be about three times narrower than that for the bulk. This strongly contrasts with a subtle variation seen in the α and β bands derived from the one-dimensional 4d_{xz/yz}. This anomaly is reproduced by the dynamical mean-field theory calculations, introducing not only the on-site Hubbard interaction but also the significant Hund's coupling. We detect a coherence-to-incoherence crossover theoretically predicted for Hund's metals, which has been recognized only recently. The crossover temperature in the surface is about half that of the bulk, indicating that the naturally generated monolayer of reconstructed Sr_{2}RuO_{4} is extremely correlated and well isolated from the underlying crystal.
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Affiliation(s)
- Takeshi Kondo
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - M Ochi
- Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - M Nakayama
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - H Taniguchi
- Department of Materials Science and Engineering, Iwate University, Morioka 020-8551, Japan
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - S Akebi
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - K Kuroda
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - M Arita
- Hiroshima Synchrotron Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan
| | - S Sakai
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - H Namatame
- Hiroshima Synchrotron Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan
| | - M Taniguchi
- Hiroshima Synchrotron Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan
- Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
| | - Y Maeno
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - R Arita
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - S Shin
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
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27
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Wang Y, Zheng X, Yang J. Kondo screening and spin excitation in few-layer CoPc molecular assembly stacking on Pb(111) surface: A DFT+HEOM study. J Chem Phys 2016; 145:154301. [DOI: 10.1063/1.4964675] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Affiliation(s)
- Yu Wang
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Xiao Zheng
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Jinlong Yang
- Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
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28
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Choi DJ, Guissart S, Ormaza M, Bachellier N, Bengone O, Simon P, Limot L. Kondo Resonance of a Co Atom Exchange Coupled to a Ferromagnetic Tip. NANO LETTERS 2016; 16:6298-6302. [PMID: 27598512 DOI: 10.1021/acs.nanolett.6b02617] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The Kondo effect of a Co atom on Cu(100) was investigated with a low-temperature scanning tunneling microscope using a monoatomically sharp nickel tip. Upon a tip-Co contact, the differential conductance spectra exhibit a spin-split asymmetric Kondo resonance. The computed ab initio value of the exchange coupling is too small to suppress the Kondo effect, but sufficiently large to produce the splitting observed. A quantitative analysis of the line shape using the numerical renormalization group technique indicates that the junction spin polarization is weak.
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Affiliation(s)
- D-J Choi
- IPCMS, CNRS UMR 7504, Université de Strasbourg , 67034 Strasbourg, France
- CIC nanoGUNE , 20018 Donostia-San Sebastián, Spain
| | - S Guissart
- Laboratoire de Physique des Solides, CNRS UMR 8502, Université Paris-Sud 11 , 91405 Orsay, France
| | - M Ormaza
- IPCMS, CNRS UMR 7504, Université de Strasbourg , 67034 Strasbourg, France
| | - N Bachellier
- IPCMS, CNRS UMR 7504, Université de Strasbourg , 67034 Strasbourg, France
| | - O Bengone
- IPCMS, CNRS UMR 7504, Université de Strasbourg , 67034 Strasbourg, France
| | - P Simon
- Laboratoire de Physique des Solides, CNRS UMR 8502, Université Paris-Sud 11 , 91405 Orsay, France
| | - L Limot
- IPCMS, CNRS UMR 7504, Université de Strasbourg , 67034 Strasbourg, France
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29
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Warner B, El Hallak F, Atodiresei N, Seibt P, Prüser H, Caciuc V, Waters M, Fisher AJ, Blügel S, van Slageren J, Hirjibehedin CF. Sub-molecular modulation of a 4f driven Kondo resonance by surface-induced asymmetry. Nat Commun 2016; 7:12785. [PMID: 27666413 PMCID: PMC5052670 DOI: 10.1038/ncomms12785] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 08/02/2016] [Indexed: 02/05/2023] Open
Abstract
Coupling between a magnetic impurity and an external bath can give rise to many-body quantum phenomena, including Kondo and Hund's impurity states in metals, and Yu-Shiba-Rusinov states in superconductors. While advances have been made in probing the magnetic properties of d-shell impurities on surfaces, the confinement of f orbitals makes them difficult to access directly. Here we show that a 4f driven Kondo resonance can be modulated spatially by asymmetric coupling between a metallic surface and a molecule containing a 4f-like moment. Strong hybridization of dysprosium double-decker phthalocyanine with Cu(001) induces Kondo screening of the central magnetic moment. Misalignment between the symmetry axes of the molecule and the surface induces asymmetry in the molecule's electronic structure, spatially mediating electronic access to the magnetic moment through the Kondo resonance. This work demonstrates the important role that molecular ligands have in mediating electronic and magnetic coupling and in accessing many-body quantum states. In the Kondo effect, a bath of conduction electrons screens a localized magnetic moment. Here, the authors demonstrate Kondo screening of a normally isolated 4f-like moment in a magnetic molecule on a Cu(001) surface that is modulated by strong ligand-mediated coupling.
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Affiliation(s)
- Ben Warner
- London Centre for Nanotechnology, University College London (UCL), London WC1H 0AH, UK.,Department of Physics &Astronomy, University College London, London WC1E 6BT, UK
| | - Fadi El Hallak
- London Centre for Nanotechnology, University College London (UCL), London WC1H 0AH, UK
| | - Nicolae Atodiresei
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, D-52425 Jülich, Germany
| | - Philipp Seibt
- London Centre for Nanotechnology, University College London (UCL), London WC1H 0AH, UK.,Department of Physics &Astronomy, University College London, London WC1E 6BT, UK
| | - Henning Prüser
- London Centre for Nanotechnology, University College London (UCL), London WC1H 0AH, UK
| | - Vasile Caciuc
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, D-52425 Jülich, Germany
| | - Michael Waters
- School of Chemistry, University of Nottingham, Nottingham NG7 2RD, UK
| | - Andrew J Fisher
- London Centre for Nanotechnology, University College London (UCL), London WC1H 0AH, UK.,Department of Physics &Astronomy, University College London, London WC1E 6BT, UK
| | - Stefan Blügel
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, D-52425 Jülich, Germany
| | - Joris van Slageren
- Institut für Physikalische Chemie, University of Stuttgart, 70569 Stuttgart, Germany
| | - Cyrus F Hirjibehedin
- London Centre for Nanotechnology, University College London (UCL), London WC1H 0AH, UK.,Department of Physics &Astronomy, University College London, London WC1E 6BT, UK.,Department of Chemistry, University College London, London WC1H 0AJ, UK
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30
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Khajetoorians AA, Steinbrecher M, Ternes M, Bouhassoune M, dos Santos Dias M, Lounis S, Wiebe J, Wiesendanger R. Tailoring the chiral magnetic interaction between two individual atoms. Nat Commun 2016; 7:10620. [PMID: 26902332 PMCID: PMC4766390 DOI: 10.1038/ncomms10620] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2015] [Accepted: 01/05/2016] [Indexed: 11/13/2022] Open
Abstract
Chiral magnets are a promising route towards dense magnetic storage technology due to their inherent nano-scale dimensions and energy efficient properties. Engineering chiral magnets requires atomic-level control of the magnetic exchange interactions, including the Dzyaloshinskii–Moriya interaction, which defines a rotational sense for the magnetization of two coupled magnetic moments. Here we show that the indirect conduction electron-mediated Dzyaloshinskii–Moriya interaction between two individual magnetic atoms on a metallic surface can be manipulated by changing the interatomic distance with the tip of a scanning tunnelling microscope. We quantify this interaction by comparing our measurements to a quantum magnetic model and ab-initio calculations yielding a map of the chiral ground states of pairs of atoms depending on the interatomic separation. The map enables tailoring the chirality of the magnetization in dilute atomic-scale magnets. The Dzyaloshinskii-Moriya exchange interaction arises in magnetic systems with broken inversion symmetry and promotes chiral magnetic order which may be exploited in spintronic devices. Here, the authors demonstrate how such an interaction between magnetic atoms on a metallic surface may be tuned by their separation.
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Affiliation(s)
- A A Khajetoorians
- Department of Physics, Hamburg University, 20355 Hamburg, Germany.,Institute for Molecules and Materials, Radboud University, 6525AJ Nijmegen, The Netherlands
| | - M Steinbrecher
- Department of Physics, Hamburg University, 20355 Hamburg, Germany
| | - M Ternes
- Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
| | - M Bouhassoune
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich &JARA, 52425 Jülich, Germany
| | - M dos Santos Dias
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich &JARA, 52425 Jülich, Germany
| | - S Lounis
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich &JARA, 52425 Jülich, Germany
| | - J Wiebe
- Department of Physics, Hamburg University, 20355 Hamburg, Germany
| | - R Wiesendanger
- Department of Physics, Hamburg University, 20355 Hamburg, Germany
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31
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Absence of a spin-signature from a single Ho adatom as probed by spin-sensitive tunneling. Nat Commun 2016; 7:10454. [PMID: 26838811 PMCID: PMC4742789 DOI: 10.1038/ncomms10454] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 12/10/2015] [Indexed: 11/08/2022] Open
Abstract
Whether rare-earth materials can be used as single-atom magnetic memory is an ongoing debate in recent literature. Here we show, by inelastic and spin-resolved scanning tunnelling-based methods, that we observe a strong magnetic signal and excitation from Fe atoms adsorbed on Pt(111), but see no signatures of magnetic excitation or spin-based telegraph noise for Ho atoms. Moreover, we observe that the indirect exchange field produced by a single Ho atom is negligible, as sensed by nearby Fe atoms. We demonstrate, using ab initio methods, that this stems from a comparatively weak coupling of the Ho 4f electrons with both tunnelling electrons and substrate-derived itinerant electrons, making both magnetic coupling and detection very difficult when compared to 3d elements. We discuss these results in the context of ongoing disputes and clarify important controversies. Magnetic stability of holmium atoms on a platinum(111) surface has recently been reported, raising prospects for atomic-scale spintronics, however contradictory results have since emerged. Here, Steinbrecher et al. find evidence for an invisibility of the holmium spin to scanning tunnelling spectroscopy techniques which challenges recent results.
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32
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Hirjibehedin CF. Magnetic atoms: The makings of a Hund's metal. NATURE NANOTECHNOLOGY 2015; 10:914-915. [PMID: 26530020 DOI: 10.1038/nnano.2015.225] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Affiliation(s)
- Cyrus F Hirjibehedin
- London Centre for Nanotechnology, Department of Physics and Astronomy, Department of Chemistry, University College London, London WC1H 0AH, UK
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