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Wätzel J, Blättermann A, Schulz D, Chiang CT, Berakdar J. Imprinting photon orbital angular momentum during laser-assisted photoemission from quantum wells. OPTICS LETTERS 2020; 45:5970-5973. [PMID: 33137043 DOI: 10.1364/ol.409206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 09/22/2020] [Indexed: 06/11/2023]
Abstract
We study theoretically the transfer of the light field orbital angular momentum (OAM) to propagating electrons upon photoemission from quantum well states. Irradiation with a Laguerre-Gaussian mode laser pulse elevates the quantum well state into a laser-dressed Volkov state that can be detected in an angular and energy-resolved manner while varying the characteristics of the driving fields. We derive the photoemission cross section for this process using the S-matrix theory and illustrate how the OAM is embodied in the photoelectron angular pattern with the aid of numerical calculations. The results point to a new type of time-resolved spectroscopy, in which the electronic orbital motion is addressed exclusively, with the potential for a new insight in spin-orbitally or orbitally coupled systems.
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Zhang H, Bao C, Jiang Z, Zhang K, Li H, Chen C, Avila J, Wu Y, Duan W, Asensio MC, Zhou S. Resolving Deep Quantum-Well States in Atomically Thin 2H-MoTe 2 Flakes by Nanospot Angle-Resolved Photoemission Spectroscopy. NANO LETTERS 2018; 18:4664-4668. [PMID: 29991260 DOI: 10.1021/acs.nanolett.8b00589] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Transition-metal dichalcogenides exhibit strong quantum confinement effects, and their electronic structure is strongly dependent on the number of layers. Resolving the thickness-dependent electronic structure is important. While the electronic structure of atomically thin 2H-MoSe2 or 2H-MoS2 have been explored, information on the experimental electronic structure of 2H-MoTe2 is still missing. Here, by using nanospot angle-resolved photoemission spectroscopy (nanoARPES), we reveal the experimental electronic structure of exfoliated 2H-MoTe2 thin flakes with different thickness (three, five, and seven monolayers). Well-separated quantum-well states are clearly observed in thin 2H-MoTe2 flakes at deep valence bands at energies between -3 to -5 eV, while those at the top of the valence band between -1 and -2 eV are much more closely spaced compared with those from 2H-MoSe2 and 2H-MoS2. First-principles calculation shows that the main difference is attributed to the weaker hybridization and smaller energy difference between Mo 4d z2 and Te 5p z orbitals as compared with Se 4p z and S 3p z orbitals. Our work demonstrates the power of nanoARPES in resolving the electronic structure of atomically thin exfoliated flakes.
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Affiliation(s)
| | | | | | | | | | - Chaoyu Chen
- Synchrotron SOLEIL , L'Orme des Merisiers, Saint Aubin-BP 48 , 91192 Gif sur Yvette Cedex , France
| | - José Avila
- Synchrotron SOLEIL , L'Orme des Merisiers, Saint Aubin-BP 48 , 91192 Gif sur Yvette Cedex , France
| | | | - Wenhui Duan
- Collaborative Innovation Center of Quantum Matter , Beijing 100084 , PR China
| | - Maria C Asensio
- Synchrotron SOLEIL , L'Orme des Merisiers, Saint Aubin-BP 48 , 91192 Gif sur Yvette Cedex , France
| | - Shuyun Zhou
- Collaborative Innovation Center of Quantum Matter , Beijing 100084 , PR China
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Manna S, Przybylski M, Sander D, Kirschner J. The role of electron confinement in Pd films for the oscillatory magnetic anisotropy in an adjacent Co layer. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:456001. [PMID: 27609044 DOI: 10.1088/0953-8984/28/45/456001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We demonstrate the interplay between quantum well states in Pd and the magnetic anisotropy in Pd/Co/Cu (0 0 1) by combined scanning tunneling spectroscopy (STS) and magneto optical Kerr effect (MOKE) measurements. Low temperature scanning tunneling spectroscopy reveals occupied and unoccupied quantum well states (QWS) in atomically flat Pd films on Co/Cu (0 0 1). These states give rise to sharp peaks in the differential conductance spectra. A quantitative analysis of the spectra reveals the electronic dispersion of the Pd (0 0 1) d-band ([Formula: see text]-type) along the [Formula: see text]-X direction. In situ MOKE experiments on Pd/Co/Cu (1, 1, 13) uncover a periodic variation of the in-plane uniaxial magnetic anisotropy as a function of Pd thickness with a period of 6 atomic layers Pd. STS shows that QWS in Pd cross the Fermi level with the same periodicity of 6 atomic layers. Backed by previous theoretical work we ascribe the variation of the magnetic anisotropy in Co to QWS in the Pd overlayer. Our results suggest a novel venue towards tailoring uniaxial magnetic anisotropy of ferromagnetic films by exploiting QWS in an adjacent material with large spin-orbit coupling.
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Affiliation(s)
- Sujit Manna
- Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany
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Saha SK, Manna S, Stepanyuk VS, Kirschner J. Visualizing Non-abrupt Transition of Quantum Well States at Stepped Silver Surfaces. Sci Rep 2015; 5:12847. [PMID: 26243639 PMCID: PMC4525284 DOI: 10.1038/srep12847] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 07/10/2015] [Indexed: 11/09/2022] Open
Abstract
We use scanning tunneling spectroscopy (STS) experiments and first-principles density functional theory (DFT) calculations to address a fundamental question of how quantum well (QW) states for electrons in a metal evolve spatially in the lateral direction when there is a surface step that changes the vertical confinement thickness. This study reveals a clear spatially dependent, nearly continuous trend in the energetic shifts of quantum well (QW) states of thin Ag(111) film grown on Cu(111) substrate, showing the strongest change near the step edge. A large energetic shift equaling up to ~200 meV with a lateral extension of the QW states of the order of ~20 Å is found, even though the step-edge is atomically sharp as evidenced by a line scan. The observed lateral extension and the nearly smooth transition of QW states are understood within the context of step-induced charge oscillation, and Smoluchowski-type charge spreading and smoothing.
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Affiliation(s)
| | - Sujit Manna
- Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle, Germany
| | | | - Jürgen Kirschner
- 1] Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle, Germany [2] Martin-Luther-Universität Halle-Wittenberg, 06120 Halle, Germany
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Dąbrowski M, Peixoto TRF, Pazgan M, Winkelmann A, Cinal M, Nakagawa T, Takagi Y, Yokoyama T, Bisio F, Bauer U, Yildiz F, Przybylski M, Kirschner J. Oscillations of the orbital magnetic moment due to d-band quantum well states. PHYSICAL REVIEW LETTERS 2014; 113:067203. [PMID: 25148348 DOI: 10.1103/physrevlett.113.067203] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2014] [Indexed: 06/03/2023]
Abstract
The effect of electron confinement on the magnetocrystalline anisotropy of ultrathin bcc Fe films is explored by combining photoemission spectroscopy, x-ray magnetic circular dichroism, and magneto-optical Kerr effect measurements. Pronounced thickness-dependent variations in the magnetocrystalline anisotropy are ascribed to periodic changes in the density of states at the Fermi level, induced by quantization of d(xz), d(yz) out-of-plane orbitals. Our results reveal a direct correlation between quantum well states, the orbital magnetic moment, and the magnetocrystalline anisotropy.
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Affiliation(s)
- M Dąbrowski
- Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle, Germany
| | - T R F Peixoto
- Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle, Germany
| | - M Pazgan
- Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle, Germany
| | - A Winkelmann
- Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle, Germany
| | - M Cinal
- Institute of Physical Chemistry, Polish Academy of Sciences, 01-224 Warsaw, Poland
| | - T Nakagawa
- Institute for Molecular Science, Myodaiji-cho, Okazaki, Aichi 444-8585, Japan
| | - Y Takagi
- Institute for Molecular Science, Myodaiji-cho, Okazaki, Aichi 444-8585, Japan
| | - T Yokoyama
- Institute for Molecular Science, Myodaiji-cho, Okazaki, Aichi 444-8585, Japan
| | - F Bisio
- CNR-SPIN Corso Perrone 24, I-16152 Genova, Italy
| | - U Bauer
- Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle, Germany
| | - F Yildiz
- Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle, Germany
| | - M Przybylski
- Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle, Germany and Faculty of Physics and Applied Computer Science, and Academic Centre for Materials and Nanotechnology, AGH University of Science and Technology, 30-059 Kraków, Poland
| | - J Kirschner
- Max-Planck-Institut für Mikrostrukturphysik, 06120 Halle, Germany and Naturwissenschaftliche Fakultät II, Martin-Luther-Universität Halle-Wittenberg, 06120 Halle, Germany
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Brovko OO, Ruiz-Díaz P, Dasa TR, Stepanyuk VS. Controlling magnetism on metal surfaces with non-magnetic means: electric fields and surface charging. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:093001. [PMID: 24523356 DOI: 10.1088/0953-8984/26/9/093001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We review the state of the art of surface magnetic property control with non-magnetic means, concentrating on metallic surfaces and techniques such as charge-doping or external electric field (EEF) application. Magneto-electric coupling via EEF-based charge manipulation is discussed as a way to tailor single adatom spins, exchange interaction between adsorbates or anisotropies of layered systems. The mechanisms of paramagnetic and spin-dependent electric field screening and the effect thereof on surface magnetism are discussed in the framework of theoretical and experimental studies. The possibility to enhance the effect of EEF by immersing the target system into an electrolyte or ionic liquid is discussed by the example of substitutional impurities and metallic alloy multilayers. A similar physics is pointed out for the case of charge traps, metallic systems decoupled from a bulk electron bath. In that case the charging provides the charge carrier density changes necessary to affect the magnetic moments and anisotropies in the system. Finally, the option of using quasi-free electrons rather than localized atomic spins for surface magnetism control is discussed with the example of Shockley-type metallic surface states confined to magnetic nanoislands.
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Affiliation(s)
- Oleg O Brovko
- Max-Planck Institut für Mikrostrukturphysik, Halle, Germany
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Yang M, Jackson KA, Jellinek J. First-principles study of intermediate size silver clusters: Shape evolution and its impact on cluster properties. J Chem Phys 2006; 125:144308. [PMID: 17042591 DOI: 10.1063/1.2351818] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Low-energy isomers of Ag(N) clusters are studied within gradient-corrected density functional theory over the size range of N = 9-20. The candidate conformations are drawn from an extensive structural database created in a recent exploration of Cu(N) clusters [M. Yang et al., J. Chem. Phys. 124, 24308 (2006)]. Layered configurations dominate the list of the lowest-energy isomers of Ag(N) for N < 16. The most stable structures for N > 16 are compact with quasispherical shapes. The size-driven shape evolution is similar to that found earlier for Na(N) and Cu(N). The shape change has a pronounced effect on the cluster cohesive energies, ionization potentials, and polarizabilities. The properties computed for the most stable isomers of Ag(N) are in good agreement with the available experimental data.
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Affiliation(s)
- M Yang
- Physics Department, Central Michigan University, Mt. Pleasant, Michigan 48859, USA
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Paggel JJ, Luh DA, Miller T, Chiang TC. Electronic-structure dependence of the electron-phonon interaction in Ag. PHYSICAL REVIEW LETTERS 2004; 92:186803. [PMID: 15169521 DOI: 10.1103/physrevlett.92.186803] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2003] [Indexed: 05/24/2023]
Abstract
The linewidths of sp- and d-band derived electronic quantum-well states in thin films of Ag on Fe(100) are measured as a function of temperature to yield the electron-phonon coupling parameters. The results vary by a factor of up to 35 among the different states. The origin of these huge differences is traced to the decay path selection for the various initial states of the holes created by the photoemission process. The electron-phonon coupling parameter for the top d-band quantum-well state, 0.015+/-0.006, is the smallest ever reported.
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Affiliation(s)
- J J Paggel
- Institut für Experimentalphysik, Freie Universität Berlin, 14195 Berlin, Germany
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Yu H, Jiang CS, Ebert P, Wang XD, White JM, Niu Q, Zhang Z, Shih CK. Quantitative determination of the metastability of flat Ag overlayers on GaAs(110). PHYSICAL REVIEW LETTERS 2002; 88:016102. [PMID: 11800970 DOI: 10.1103/physrevlett.88.016102] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2000] [Indexed: 05/23/2023]
Abstract
Atomically flat ultrathin Ag films on GaAs(110) can be formed through a kinetic pathway. However, such films are metastable and will transform to 3D islands upon high temperature annealing. Using scanning tunneling microscopy, we have measured quantitatively the layer-resolved metastability of flat Ag overlayers as they evolve toward their stable state, and deduced the corresponding kinetic barrier the system has to overcome in reaching the stable state. These results indicate that the metastability of the Ag overlayer is defined by the quantum nature of the conduction electrons confined within the overlayer.
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Affiliation(s)
- Hongbin Yu
- Department of Physics, The University of Texas at Austin, Austin, TX 78712, USA
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