1
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Wang X, Zhu X, Wu P, Li Q, Li Z, Zhang X, Liu Z, Zhang Y, Du P. Differences in Kondo Splitting of Surface Quantum Systems Induced by Two Distinct Magnetic Tips: A Joint Method of DFT and HEOM. J Phys Chem A 2024; 128:4750-4760. [PMID: 38832647 DOI: 10.1021/acs.jpca.4c02067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2024]
Abstract
The interactions between a magnetic tip and local spin impurities initiate unconventional Kondo phenomena, such as asymmetric suppression or even splitting of the Kondo peak. However, a lack of realistic theoretical models and comprehensive explanations for this phenomenon persists due to the complexity of the interactions. This research employs a joint method of density functional theory (DFT) and hierarchical equation of motion (HEOM) to simulate and contrast the modulation of the spin state and Kondo behavior in the Fe/Cu(100) system with two distinct magnetic tips. A cobalt tip, possessing a larger magnetic moment, incites greater atomic displacement of the iron atom, more notable alterations in electronic structure, and enhanced charge transfer with the environment compared with the control process utilizing a nickel tip. Furthermore, the Kondo resonance undergoes asymmetric splitting as a result of the ferromagnetic correlation between the iron atom and the magnetic tip. The Co tip's higher spin polarization results in a wider spacing between the splitting peaks. This investigation underscores the precision of the DFT + HEOM approach in predicting complex quantum phenomena and explaining the underlying physical principles. This provides valuable theoretical support for developing more sophisticated quantum regulation experiments.
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Affiliation(s)
- Xiaoli Wang
- Shandong Provincial Key Laboratory of Monocrystalline Silicon Semiconductor Materials and Technology, College of Chemistry and Chemical Engineering, Dezhou University, Dezhou 253023, PR China
| | - Xinru Zhu
- Shandong Provincial Key Laboratory of Monocrystalline Silicon Semiconductor Materials and Technology, College of Chemistry and Chemical Engineering, Dezhou University, Dezhou 253023, PR China
| | - Ping Wu
- Shandong Provincial Key Laboratory of Monocrystalline Silicon Semiconductor Materials and Technology, College of Chemistry and Chemical Engineering, Dezhou University, Dezhou 253023, PR China
| | - Qing Li
- Shandong Provincial Key Laboratory of Monocrystalline Silicon Semiconductor Materials and Technology, College of Chemistry and Chemical Engineering, Dezhou University, Dezhou 253023, PR China
| | - Zhen Li
- Shandong Provincial Key Laboratory of Monocrystalline Silicon Semiconductor Materials and Technology, College of Chemistry and Chemical Engineering, Dezhou University, Dezhou 253023, PR China
| | - Xiaolei Zhang
- Shandong Provincial Key Laboratory of Monocrystalline Silicon Semiconductor Materials and Technology, College of Chemistry and Chemical Engineering, Dezhou University, Dezhou 253023, PR China
| | - Zhongmin Liu
- Shandong Provincial Key Laboratory of Monocrystalline Silicon Semiconductor Materials and Technology, College of Chemistry and Chemical Engineering, Dezhou University, Dezhou 253023, PR China
| | - Yuexing Zhang
- Shandong Provincial Key Laboratory of Monocrystalline Silicon Semiconductor Materials and Technology, College of Chemistry and Chemical Engineering, Dezhou University, Dezhou 253023, PR China
| | - Pengli Du
- College of Chemical Engineering, Qinghai University, Xining 810016, PR China
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2
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Zuo L, Zhuang Q, Ye L, Yan Y, Zheng X. Unveiling the Decisive Factor for the Sharp Transition in the Scanning Tunneling Spectroscopy of a Single Nickelocene Molecule. J Phys Chem Lett 2022; 13:11262-11270. [PMID: 36448930 DOI: 10.1021/acs.jpclett.2c03168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Scanning tunneling microscopy (STM) has been utilized to realize the precise measurement and control of local spin states. Experiments have demonstrated that when a nickelocene (Nc) molecule is attached to the apex of an STM tip, the dI/dV spectra exhibit a sharp or a smooth transition when the tip is displaced toward the substrate. However, what leads to the two distinct types of transitions remains unclear, and more intriguingly, the physical origin of the abrupt change in the line shape of dI/dV spectra remains unclear. To clarify these intriguing issues, we perform first-principles-based simulations on the STM tip control process for the Cu tip/Nc/Cu(100) junction. In particular, we find that the suddenly enhanced hybridization between the d orbitals on the Ni ion and the metallic bands in the substrate leads to Kondo correlation overwhelming spin excitation, which is the main cause of the sharp transition in the dI/dV spectra observed experimentally.
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Affiliation(s)
- Lijun Zuo
- Hefei National Research Center 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
| | - Qingfeng Zhuang
- Hefei National Research Center 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
| | - Lyuzhou Ye
- Hefei National Research Center 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
| | - YiJing Yan
- Hefei National Research Center for Physical Sciences at the Microscale and iChEM, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Xiao Zheng
- Department of Chemistry, Fudan University, Shanghai 200433, China
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3
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Zhuang Q, Wang X, Ye L, Yan Y, Zheng X. Origin of Asymmetric Splitting of Kondo Peak in Spin-Polarized Scanning Tunneling Spectroscopy: Insights from First-Principles-Based Simulations. J Phys Chem Lett 2022; 13:2094-2100. [PMID: 35225612 DOI: 10.1021/acs.jpclett.2c00228] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The spin-polarized scanning tunneling microscope (SP-STM) has served as a versatile tool for probing and manipulating the spintronic properties of atomic and molecular devices with high precision. The interplay between the local spin state and its surrounding magnetic environment significantly affects the transport behavior of the device. Particularly, in the contact regime, the strong hybridization between the SP-STM tip and the magnetic atom or molecule could give rise to unconventional Kondo resonance signatures in the differential conductance (dI/dV) spectra. This poses challenges for the simulation of a realistic tip control process. By combining the density functional theory and the hierarchical equations of motion methods, we achieve first-principles-based simulation of the control of a Ni-tip/Co/Cu(100) junction in both the tunneling and contact regimes. The calculated dI/dV spectra reproduce faithfully the experimental data. A cotunneling mechanism is proposed to elucidate the physical origin of the observed unconventional Kondo signatures.
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Affiliation(s)
- Qingfeng Zhuang
- Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Xiaoli Wang
- School of Chemistry and Chemical Engineering, Dezhou University, Dezhou, Shandong 253023, China
| | - Lyuzhou Ye
- Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - YiJing Yan
- Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Xiao Zheng
- Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Key Laboratory of Surface and Interface Chemistry and Energy Catalysis of Anhui Higher Education Institutes, University of Science and Technology of China, Hefei, Anhui 230026, China
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4
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Fernández J, Roura-Bas P, Aligia AA. Theory of Differential Conductance of Co on Cu(111) Including Co s and d Orbitals, and Surface and Bulk Cu States. PHYSICAL REVIEW LETTERS 2021; 126:046801. [PMID: 33576682 DOI: 10.1103/physrevlett.126.046801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 01/07/2021] [Indexed: 06/12/2023]
Abstract
We revisit the theory of the Kondo effect observed by a scanning-tunneling microscope (STM) for transition-metal atoms (TMAs) on noble-metal surfaces, including d and s orbitals of the TMA, surface and bulk conduction states of the metal, and their hopping to the tip of the STM. Fitting the experimentally observed STM differential conductance for Co on Cu(111) including both the Kondo feature near the Fermi energy and the resonance below the surface band, we conclude that the STM senses mainly the Co s orbital and that the Kondo antiresonance is due to interference between states with electrons in the s orbital and a localized d orbital mediated by the conduction states.
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Affiliation(s)
- J Fernández
- Centro Atómico Bariloche, Comisión Nacional de Energía Atómica, 8400 Bariloche, Argentina, Instituto Balseiro, Comisión Nacional de Energía Atómica, 8400 Bariloche, Argentina and Consejo Nacional de Investigaciones Científicas y Técnicas, 1025 CABA, Argentina
| | - P Roura-Bas
- Centro Atómico Bariloche, Comisión Nacional de Energía Atómica, 8400 Bariloche, Argentina, Instituto Balseiro, Comisión Nacional de Energía Atómica, 8400 Bariloche, Argentina and Consejo Nacional de Investigaciones Científicas y Técnicas, 1025 CABA, Argentina
| | - A A Aligia
- Centro Atómico Bariloche, Comisión Nacional de Energía Atómica, 8400 Bariloche, Argentina, Instituto Balseiro, Comisión Nacional de Energía Atómica, 8400 Bariloche, Argentina and Consejo Nacional de Investigaciones Científicas y Técnicas, 1025 CABA, Argentina
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5
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Néel N, Shao B, Wehling TO, Kröger J. Manipulation of the two-site Kondo effect in linear CoCu n CoCu m clusters. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:055303. [PMID: 31604345 DOI: 10.1088/1361-648x/ab4d17] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Artificially assembled linear atomic clusters, CoCu n CoCu m , are used to explore variations of the Kondo effect at the two Co sites. For all investigated Cu n chain lengths ([Formula: see text]) the addition of a single Cu atom to one edge Co atom of the chain ([Formula: see text]) strongly reduces the amplitude of the Abrikosov-Suhl-Kondo resonance of that Co atom. Concomitantly, the resonance line width is more than halved. On the contrary, the Kondo effect of the opposite edge Co atom remains unaffected. Hybridization together with the linear geometry of the cluster are likely to drive the effect.
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Affiliation(s)
- N Néel
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
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6
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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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7
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Nowakowski K, Zandvliet HJW, Bampoulis P. Barrier Inhomogeneities in Atomic Contacts on WS 2. NANO LETTERS 2019; 19:1190-1196. [PMID: 30582818 DOI: 10.1021/acs.nanolett.8b04636] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The down-scaling of electrical components requires a proper understanding of the physical mechanisms governing charge transport. Here, we have investigated atomic-scale contacts and their transport characteristics on WS2 using conductive atomic force microscopy (c-AFM). We demonstrate that c-AFM can provide true atomic resolution, revealing atom vacancies, adatoms, and periodic modulations arising from electronic effects. Moreover, we find a lateral variation of the surface conductivity that arises from the lattice periodicity of WS2. Three distinct sites are identified, i.e., atop, bridge, and hollow. The current transport across these atomic metal-semiconductor interfaces is understood by considering thermionic emission and Fowler-Nordheim tunnelling. Current modulations arising from point defects and the contact geometry promise a novel route for the direct control of atomic point contacts in diodes and devices.
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Affiliation(s)
- Krystian Nowakowski
- Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology , University of Twente , P.O. Box 217, 7500AE Enschede , The Netherlands
| | - Harold J W Zandvliet
- Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology , University of Twente , P.O. Box 217, 7500AE Enschede , The Netherlands
| | - Pantelis Bampoulis
- Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology , University of Twente , P.O. Box 217, 7500AE Enschede , The Netherlands
- Physikalisches Institut , Universität zu Köln , Zülpicher Straße 77 , 50937 Köln , Germany
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8
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Gruber M, Weismann A, Berndt R. The Kondo resonance line shape in scanning tunnelling spectroscopy: instrumental aspects. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:424001. [PMID: 30191885 DOI: 10.1088/1361-648x/aadfa3] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In the scanning tunnelling microscope, the many-body Kondo effect leads to a zero-bias feature of the differential conductance spectra of magnetic adsorbates on surfaces. The intrinsic line shape of this Kondo resonance and its temperature dependence in principle contain valuable information. We use measurements on a molecular Kondo system, all- trans retinoic acid on Au(1 1 1), and model calculations to discuss the role of instrumental broadening. The modulation voltage used for the lock-in detection, noise on the sample voltage, and the temperature of the microscope tip are considered. These sources of broadening affect the apparent line shapes and render difficult a determination of the intrinsic line width, in particular when variable temperatures are involved.
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Affiliation(s)
- Manuel Gruber
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany
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9
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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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10
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Hiraoka R, Minamitani E, Arafune R, Tsukahara N, Watanabe S, Kawai M, Takagi N. Single-molecule quantum dot as a Kondo simulator. Nat Commun 2017; 8:16012. [PMID: 28665404 PMCID: PMC5497065 DOI: 10.1038/ncomms16012] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2016] [Accepted: 05/24/2017] [Indexed: 11/08/2022] Open
Abstract
Structural flexibility of molecule-based systems is key to realizing the novel functionalities. Tuning the structure in the atomic scale enables us to manipulate the quantum state in the molecule-based system. Here we present the reversible Hamiltonian manipulation in a single-molecule quantum dot consisting of an iron phthalocyanine molecule attached to an Au electrode and a scanning tunnelling microscope tip. We precisely controlled the position of Fe2+ ion in the molecular cage by using the tip, and tuned the Kondo coupling between the molecular spins and the Au electrode. Then, we realized the crossover between the strong-coupling Kondo regime and the weak-coupling regime governed by spin-orbit interaction in the molecule. The results open an avenue to simulate low-energy quantum many-body physics and quantum phase transition through the molecular flexibility.
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Affiliation(s)
- R. Hiraoka
- Department of Advanced Materials Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
| | - E. Minamitani
- Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - R. Arafune
- International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 304-0044, Japan
| | - N. Tsukahara
- Department of Advanced Materials Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
| | - S. Watanabe
- Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - M. Kawai
- Department of Advanced Materials Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
| | - N. Takagi
- Department of Advanced Materials Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan
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11
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Kuang G, Zhang Q, Lin T, Pang R, Shi X, Xu H, Lin N. Mechanically-Controlled Reversible Spin Crossover of Single Fe-Porphyrin Molecules. ACS NANO 2017; 11:6295-6300. [PMID: 28498652 DOI: 10.1021/acsnano.7b02567] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Spin-crossover (SCO) molecules are thought to be ideal systems for molecular spintronics when SCO can be precisely controlled at the single-molecule level. This is demonstrated here in the single-molecule junctions of Fe-porphyrin formed in a scanning tunneling microscope. Experimentally, we find that the junctions feature a zero-bias resonance in molecular conductance associated with the Fe spin center. When mechanically stretching or squeezing the junctions by adjusting the tip height, the line shape of the zero-bias resonance varies reversibly. First-principles calculations reveal that widening the junction gap by 2 Å transforms the macrocyclic core hosting the Fe center from a saddle to a planar conformation. This conformational change shortens the Fe-N bonds by 3%, which changes the Fe spin state from S = 2 to S = 1.
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Affiliation(s)
- Guowen Kuang
- Department of Physics, The Hong Kong University of Science and Technology , Hong Kong, China
| | - Qiushi Zhang
- Department of Physics, The Hong Kong University of Science and Technology , Hong Kong, China
| | - Tao Lin
- Department of Physics, The Hong Kong University of Science and Technology , Hong Kong, China
| | - Rui Pang
- Department of Physics, Southern University of Science and Technology of China , Nanshan District, Shenzhen, Guangdong 518055, China
| | - Xingqiang Shi
- Department of Physics, Southern University of Science and Technology of China , Nanshan District, Shenzhen, Guangdong 518055, China
| | - Hu Xu
- Department of Physics, Southern University of Science and Technology of China , Nanshan District, Shenzhen, Guangdong 518055, China
| | - Nian Lin
- Department of Physics, The Hong Kong University of Science and Technology , Hong Kong, China
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12
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Maughan B, Zahl P, Sutter P, Monti OLA. Ensemble Control of Kondo Screening in Molecular Adsorbates. J Phys Chem Lett 2017; 8:1837-1844. [PMID: 28383923 DOI: 10.1021/acs.jpclett.7b00278] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Switching the magnetic properties of organic semiconductors on a metal surface has thus far largely been limited to molecule-by-molecule tip-induced transformations in scanned probe experiments. Here we demonstrate with molecular resolution that collective control of activated Kondo screening can be achieved in thin-films of the organic semiconductor titanyl phthalocyanine on Cu(110) to obtain tunable concentrations of Kondo impurities. Using low-temperature scanning tunneling microscopy and spectroscopy, we show that a thermally activated molecular distortion dramatically shifts surface-molecule coupling and enables ensemble-level control of Kondo screening in the interfacial spin system. This is accompanied by the formation of a temperature-dependent Abrikosov-Suhl-Kondo resonance in the local density of states of the activated molecules. This enables coverage-dependent control over activation to the Kondo screening state. Our study thus advances the versatility of molecular switching for Kondo physics and opens new avenues for scalable bottom-up tailoring of the electronic structure and magnetic texture of organic semiconductor interfaces at the nanoscale.
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Affiliation(s)
- Bret Maughan
- University of Arizona , Department of Chemistry & Biochemistry, 1306 East University Boulevard, Tucson, Arizona 85721, United States
| | - Percy Zahl
- Brookhaven National Laboratory , Center for Functional Nanomaterials, Upton, New York 11973, United States
| | - Peter Sutter
- Brookhaven National Laboratory , Center for Functional Nanomaterials, Upton, New York 11973, United States
- Department of Electrical & Computer Engineering, University of Nebraska-Lincoln , Lincoln, Nebraska 68588, United States
| | - Oliver L A Monti
- University of Arizona , Department of Chemistry & Biochemistry, 1306 East University Boulevard, Tucson, Arizona 85721, United States
- University of Arizona , Department of Physics, 1118 East Fourth Street, Tucson, Arizona 85721, United States
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13
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Jacobson P, Muenks M, Laskin G, Brovko O, Stepanyuk V, Ternes M, Kern K. Potential energy-driven spin manipulation via a controllable hydrogen ligand. SCIENCE ADVANCES 2017; 3:e1602060. [PMID: 28439541 PMCID: PMC5392040 DOI: 10.1126/sciadv.1602060] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Accepted: 02/19/2017] [Indexed: 05/30/2023]
Abstract
Spin-bearing molecules can be stabilized on surfaces and in junctions with desirable properties, such as a net spin that can be adjusted by external stimuli. Using scanning probes, initial and final spin states can be deduced from topographic or spectroscopic data, but how the system transitions between these states is largely unknown. We address this question by manipulating the total spin of magnetic cobalt hydride complexes on a corrugated boron nitride surface with a hydrogen-functionalized scanning probe tip by simultaneously tracking force and conductance. When the additional hydrogen ligand is brought close to the cobalt monohydride, switching between a correlated S = 1/2 Kondo state, where host electrons screen the magnetic moment, and an S = 1 state with magnetocrystalline anisotropy is observed. We show that the total spin changes when the system is transferred onto a new potential energy surface that is defined by the position of the hydrogen in the junction. These results show how and why chemically functionalized tips are an effective tool to manipulate adatoms and molecules and a promising new method to selectively tune spin systems.
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Affiliation(s)
- Peter Jacobson
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
| | - Matthias Muenks
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
| | - Gennadii Laskin
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
| | - Oleg Brovko
- Abdus Salam International Centre for Theoretical Physics, Trieste, Italy
| | - Valeri Stepanyuk
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120, Halle (Saale), Germany
| | - Markus Ternes
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
| | - Klaus Kern
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
- Institut de Physique, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
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14
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Choi DJ, Abufager P, Limot L, Lorente N. From tunneling to contact in a magnetic atom: The non-equilibrium Kondo effect. J Chem Phys 2017. [DOI: 10.1063/1.4972874] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Deung-Jang Choi
- CIC nanoGUNE, Tolosa Hiribidea 78, 20018 Donostia-San Sebastian, Spain and IPCMS, CNRS UMR 7504, Université de Strasbourg, 67034 Strasbour, France
| | - Paula Abufager
- Instituto de Física de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Universidad Nacional de Rosario, Bv. 27 de Febrero 210 BIS, 2000 Rosario, Argentina
| | - Laurent Limot
- IPCMS, CNRS UMR 7504, Université de Strasbourg, 67034 Strasbourg, France
| | - Nicolás Lorente
- Centro de Física de Materiales CFM/MPC (CSIC-UPV/EHU), Paseo Manuel de Lardizabal 5, 20018 Donostia-San Sebastián, Spain and Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián, Spain
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15
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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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16
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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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17
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Meierott S, Hotz T, Néel N, Kröger J. Asymmetry parameter of peaked Fano line shapes. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2016; 87:103901. [PMID: 27802729 DOI: 10.1063/1.4963678] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The spectroscopic line shape of electronic and vibrational excitations is ubiquitously described by a Fano profile. In the case of nearly symmetric and peaked Fano line shapes, the fit of the conventional Fano function to experimental data leads to difficulties in unambiguously extracting the asymmetry parameter, which may vary over orders of magnitude without degrading the quality of the fit. Moreover, the extracted asymmetry parameter depends on initially guessed values. Using the spectroscopic signature of the single-Co Kondo effect on Au(110) the ambiguity of the extracted asymmetry parameter is traced to the highly symmetric resonance profile combined with the inevitable scattering of experimental data. An improved parameterization of the conventional Fano function is suggested that enables the nonlinear optimization in a reduced parameter space. In addition, the presence of a global minimum in the sum of squared residuals and thus the independence of start parameters may conveniently be identified in a two-dimensional plot. An angular representation of the asymmetry parameter is suggested in order to reliably determine uncertainty margins via linear error propagation.
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Affiliation(s)
- S Meierott
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
| | - T Hotz
- Institut für Mathematik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
| | - N Néel
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
| | - J Kröger
- Institut für Physik, Technische Universität Ilmenau, D-98693 Ilmenau, Germany
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18
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Hong IP, Li N, Zhang YJ, Wang H, Song HJ, Bai ML, Zhou X, Li JL, Gu GC, Zhang X, Chen M, Gottfried JM, Wang D, Lü JT, Peng LM, Hou SM, Berndt R, Wu K, Wang YF. Vacuum synthesis of magnetic aluminum phthalocyanine on Au(111). Chem Commun (Camb) 2016; 52:10338-41. [PMID: 27406881 DOI: 10.1039/c6cc03359h] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Air-unstable magnetic aluminum phthalocyanine (AlPc) molecules are prepared by an on-surface metalation reaction of phthalocyanine with aluminum (Al) atoms on Au(111) in ultrahigh vacuum. Experiments and density functional theory calculations show that an unpaired spin is located on the conjugated isoindole lobes of the molecule rather than at the Al position.
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Affiliation(s)
- I-Po Hong
- Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871, China.
| | - Na Li
- Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871, China.
| | - Ya-Jie Zhang
- BNLMS, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
| | - Hao Wang
- Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871, China.
| | - Huan-Jun Song
- BNLMS, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
| | - Mei-Lin Bai
- Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871, China.
| | - Xiong Zhou
- BNLMS, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
| | - Jian-Long Li
- BNLMS, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
| | - Gao-Chen Gu
- Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871, China.
| | - Xue Zhang
- Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871, China.
| | - Min Chen
- Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Str., 35032 Marburg, Germany
| | - J Michael Gottfried
- Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Str., 35032 Marburg, Germany
| | - Dong Wang
- Institute of Chemistry, the Chinese Academy of Science (CAS), Beijing National Laboratory for Molecular Sciences, Beijing 100190, China
| | - Jing-Tao Lü
- School of Physics, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan 430074, China
| | - Lian-Mao Peng
- Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871, China.
| | - Shi-Min Hou
- Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871, China. and Beida Information Research (BIR), Tianjin 300457, China
| | - Richard Berndt
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany
| | - Kai Wu
- BNLMS, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
| | - Yong-Feng Wang
- Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871, China. and Beida Information Research (BIR), Tianjin 300457, China
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19
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Karan S, Berndt R. Generation of spin in single cholesterol molecules on gold. Phys Chem Chem Phys 2016; 18:9334-7. [PMID: 26948454 DOI: 10.1039/c5cp07410j] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Compact islands of cholesterol on Au(111) were investigated with scanning tunneling microscopy at ∼5 K. Single molecules have been switched among several states, three of which exhibit a sharp spectroscopic feature at the Fermi level. This feature signals the presence of a localized spin and suggests that the molecule may be controllably switched between paramagnetic and diamagnetic states.
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Affiliation(s)
- Sujoy Karan
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany.
| | - Richard Berndt
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany.
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20
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Ormaza M, Robles R, Bachellier N, Abufager P, Lorente N, Limot L. On-Surface Engineering of a Magnetic Organometallic Nanowire. NANO LETTERS 2016; 16:588-593. [PMID: 26650920 DOI: 10.1021/acs.nanolett.5b04280] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The manipulation of the molecular spin state by atom doping is an attractive strategy to confer desirable magnetic properties to molecules. Here, we present the formation of novel magnetic metallocenes by following this approach. In particular, two different on-surface procedures to build isolated and layer-integrated Co-ferrocene (CoFc) molecules on a metallic substrate via atomic manipulation and atom deposition are shown. The structure as well as the electronic properties of the so-formed molecule are investigated combining scanning tunneling microscopy and spectroscopy with density functional theory calculations. It is found that unlike single ferrocene a CoFc molecule possesses a magnetic moment as revealed by the Kondo effect. These results correspond to the first controlled procedure toward the development of tailored metallocene-based nanowires with a desired chemical composition, which are predicted to be promising materials for molecular spintronics.
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Affiliation(s)
- Maider Ormaza
- IPCMS, CNRS UMR 7504, Université de Strasbourg , 67034 Strasbourg, France
| | - Roberto Robles
- ICN2 - Institut Català de Nanociéncia i Nanotecnologia , Campus UAB, 08193 Bellaterra (Barcelona), Spain
| | - Nicolas Bachellier
- IPCMS, CNRS UMR 7504, Université de Strasbourg , 67034 Strasbourg, France
| | - Paula Abufager
- ICN2 - Institut Català de Nanociéncia i Nanotecnologia , Campus UAB, 08193 Bellaterra (Barcelona), Spain
- Instituto de Física de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Universidad Nacional de Rosario , Avenida Pellegrini 250 (2000) Rosario, Argentina
| | - Nicolás Lorente
- ICN2 - Institut Català de Nanociéncia i Nanotecnologia , Campus UAB, 08193 Bellaterra (Barcelona), Spain
- Centro de Física 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, 20018 Donostia-San Sebastián, Spain
| | - Laurent Limot
- IPCMS, CNRS UMR 7504, Université de Strasbourg , 67034 Strasbourg, France
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21
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Li N, Wang H, Song DL, Li C, Li R, Hou SM, Wang YF, Berndt R. Charging single Co atoms on ultrathin NaCl films. Dalton Trans 2016; 45:16566-16569. [DOI: 10.1039/c6dt01963c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Single Co adatoms adsorbed on a double-layer NaCl film were negatively charged after applying a positive voltage pulse by STM.
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Affiliation(s)
- Na Li
- Key Laboratory for the Physics and Chemistry of Nanodevices
- Department of Electronics
- Peking University
- Beijing 100871
- China
| | - Hao Wang
- Key Laboratory for the Physics and Chemistry of Nanodevices
- Department of Electronics
- Peking University
- Beijing 100871
- China
| | - Dao-Liang Song
- Key Laboratory for the Physics and Chemistry of Nanodevices
- Department of Electronics
- Peking University
- Beijing 100871
- China
| | - Chao Li
- Key Laboratory for the Physics and Chemistry of Nanodevices
- Department of Electronics
- Peking University
- Beijing 100871
- China
| | - Ruoning Li
- Key Laboratory for the Physics and Chemistry of Nanodevices
- Department of Electronics
- Peking University
- Beijing 100871
- China
| | - Shi-Min Hou
- Key Laboratory for the Physics and Chemistry of Nanodevices
- Department of Electronics
- Peking University
- Beijing 100871
- China
| | - Yong-Feng Wang
- Key Laboratory for the Physics and Chemistry of Nanodevices
- Department of Electronics
- Peking University
- Beijing 100871
- China
| | - Richard Berndt
- Institut für Experimentelle und Angewandte Physik
- Christian-Albrechts-Universität zu Kiel
- D-24098 Kiel
- Germany
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22
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Zhang Q, Kuang G, Pang R, Shi X, Lin N. Switching Molecular Kondo Effect via Supramolecular Interaction. ACS NANO 2015; 9:12521-12528. [PMID: 26568262 DOI: 10.1021/acsnano.5b06120] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We apply supramolecular assembly to control the adsorption configuration of Co-porphyrin molecules on Au(111) and Cu(111) surfaces. By means of cryogenic scanning tunneling microscopy, we reveal that the Kondo effect associated with the Co center is absent or present in different supramolecular systems. We perform first-principles calculations to obtain spin-polarized electronic structures and compute the Kondo temperatures using the Anderson impurity model. The switching behavior is traced to varied molecular adsorption heights in different supramolecular structures. These findings unravel that a competition between intermolecular interactions and molecule-substrate interactions subtly regulates the molecular Kondo effect in supramolecular systems.
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Affiliation(s)
- Qiushi Zhang
- Department of Physics, The Hong Kong University of Science and Technology , Hong Kong, China
| | - Guowen Kuang
- Department of Physics, The Hong Kong University of Science and Technology , Hong Kong, China
| | - Rui Pang
- Department of Physics, South University of Science and Technology of China , Shenzhen 518055, China
| | - Xingqiang Shi
- Department of Physics, South University of Science and Technology of China , Shenzhen 518055, China
| | - Nian Lin
- Department of Physics, The Hong Kong University of Science and Technology , Hong Kong, China
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23
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Heinrich BW, Braun L, Pascual JI, Franke KJ. Tuning the Magnetic Anisotropy of Single Molecules. NANO LETTERS 2015; 15:4024-8. [PMID: 25942560 DOI: 10.1021/acs.nanolett.5b00987] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The magnetism of single atoms and molecules is governed by the atomic scale environment. In general, the reduced symmetry of the surrounding splits the d states and aligns the magnetic moment along certain favorable directions. Here, we show that we can reversibly modify the magnetocrystalline anisotropy by manipulating the environment of single iron(II) porphyrin molecules adsorbed on Pb(111) with the tip of a scanning tunneling microscope. When we decrease the tip-molecule distance, we first observe a small increase followed by an exponential decrease of the axial anisotropy on the molecules. This is in contrast to the monotonous increase observed earlier for the same molecule with an additional axial Cl ligand ( Nat. Phys. 2013 , 9 , 765 ). We ascribe the changes in the anisotropy of both species to a deformation of the molecules in the presence of the attractive force of the tip, which leads to a change in the d level alignment. These experiments demonstrate the feasibility of a precise tuning of the magnetic anisotropy of an individual molecule by mechanical control.
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Affiliation(s)
- Benjamin W Heinrich
- †Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Lukas Braun
- †Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Jose I Pascual
- †Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
- ‡CIC nanoGUNE, 20018 Donostia-San Sebastián, Spain
- §Ikerbasque, Basque Foundation for Science, 48011 Bilbao, Spain
| | - Katharina J Franke
- †Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
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24
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Kim H, Hasegawa Y. Site-Dependent Evolution of Electrical Conductance from Tunneling to Atomic Point Contact. PHYSICAL REVIEW LETTERS 2015; 114:206801. [PMID: 26047248 DOI: 10.1103/physrevlett.114.206801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Indexed: 06/04/2023]
Abstract
Using scanning tunneling microscopy (STM), we investigated the evolution of electrical conductance between a Pb tip and Pb(111) surface from tunneling to atomic point contact at a site that was defined with atomic precision. We found that the conductance evolution depended on the contact site, for instance, on-top, bridge, or hollow (hcp and fcc) sites in the Pb lattice. In the transition from tunneling to contact regimes, the conductance measured at the on-top site was enhanced. In the point contact regime, the hollow sites had conductances larger than those of the other sites, and between the hollow sites, the hcp site had a conductance larger than that of the fcc site. We also observed the enhancement and reversal of the apparent height in atomically resolved high-current STM images, consistent with the results of the conductance traces. Our results indicate the importance of atomic configuration in the conductance of atomic junctions and suggest that attractive chemical interactions have a significant role in electron transport between contacting atoms.
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Affiliation(s)
- Howon Kim
- Institute for Solid State Physics, University of Tokyo 5-1-5, Kashiwa-no-ha, Kashiwa 277-8581, Japan
| | - Yukio Hasegawa
- Institute for Solid State Physics, University of Tokyo 5-1-5, Kashiwa-no-ha, Kashiwa 277-8581, Japan
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25
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Schneider NL, Néel N, Andersen NP, Lü JT, Brandbyge M, Kröger J, Berndt R. Spectroscopy of transmission resonances through a C₆₀ junction. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:015001. [PMID: 25407046 DOI: 10.1088/0953-8984/27/1/015001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Electron transport through a single C60 molecule on Cu(1 1 1) has been investigated with a scanning tunnelling microscope in tunnelling and contact ranges. Single-C60 junctions have been fabricated by establishing a contact between the molecule and the tip, which is reflected by a down-shift in the lowest unoccupied molecular orbital resonance. These junctions are stable even at elevated bias voltages enabling conductance measurements at high voltages and nonlinear conductance spectroscopy in tunnelling and contact ranges. Spectroscopy and first principles transport calculations clarify the relation between molecular orbital resonances and the junction conductance. Due to the strong molecule-electrode coupling the simple picture of electron transport through individual orbitals does not hold.
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Affiliation(s)
- N L Schneider
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany
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26
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Lin T, Kuang G, Wang W, Lin N. Two-dimensional lattice of out-of-plane dinuclear iron centers exhibiting Kondo resonance. ACS NANO 2014; 8:8310-8316. [PMID: 25084448 DOI: 10.1021/nn502765g] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We present an investigation of two-dimensional coordination networks formed by 5,10,15,20-tetra(4-pyridyl)porphyrin and iron atoms on a Au(111) surface. The coordination bonds are very robust as evidenced by STM manipulated lateral displacement of an entire network of islands consisting of hundreds of molecules and atoms. We also applied vertical manipulation to detach and attach single Fe atoms at the coordination sites. Moreover, low-temperature tunneling spectroscopy reveals a Kondo resonance at the Fe coordination center. These findings evidence that the network structure is stabilized by a coordination motif in which a pair of vertically aligned Fe atoms is ligated by four equatorial pyridyl groups. Such out-of-plane dinuclear coordination centers provide potential functions, such as catalytic, adsorption, and template for growing three-dimensional framework architectures.
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Affiliation(s)
- Tao Lin
- Department of Physics, The Hong Kong University of Science and Technology , Clear Water Bay, Hong Kong
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27
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Ren J, Guo H, Pan J, Zhang YY, Wu X, Luo HG, Du S, Pantelides ST, Gao HJ. Kondo effect of cobalt adatoms on a graphene monolayer controlled by substrate-induced ripples. NANO LETTERS 2014; 14:4011-4015. [PMID: 24905855 DOI: 10.1021/nl501425n] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The Kondo effect, a widely studied phenomenon in which the scattering of conduction electrons by magnetic impurities increases as the temperature T is lowered, depends strongly on the density of states at the Fermi energy. It has been predicted by theory that magnetic impurities on free-standing monolayer graphene exhibit the Kondo effect and that control of the density of states at the Fermi level by external means can be used to switch the effect on and off. However, though transport data for Co adatoms on graphene monolayers on several substrates have been reported, there exists no evidence for a Kondo effect. Here we probe the role of the substrate on the Kondo effect of Co on graphene by combining low-temperature scanning tunneling microscopy and spectroscopy measurements with density functional theory calculations. We use a Ru(0001) substrate that is known to cause graphene to ripple, yielding a moiré superlattice. The experimental data show a sharp Kondo resonance peak near the Fermi energy from only Co adatoms at the edge of atop regions of the moiré pattern. The theoretical results show that the variation of the distance from the graphene to the Ru substrate, which controls the spin polarization and local density of states at the Fermi energy, is the key factor for the appearance of the Kondo resonance. The results suggest that rippling of graphene by suitable substrates is an additional lever for tuning and selectively switching the appearance of the Kondo effect.
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Affiliation(s)
- Jindong Ren
- Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China
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