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Lopes V, Chiappe G, Ribeiro LC, Anda EV. Totally Spin-Polarized Currents in an Interferometer with Spin-Orbit Coupling and the Absence of Magnetic Field Effects. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:4082. [PMID: 36432367 PMCID: PMC9696532 DOI: 10.3390/nano12224082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 11/14/2022] [Accepted: 11/16/2022] [Indexed: 06/16/2023]
Abstract
The paper studies the electronic current in a one-dimensional lead under the effect of spin-orbit coupling and its injection into a metallic conductor through two contacts, forming a closed loop. When an external potential is applied, the time reversal symmetry is broken and the wave vector k of the circulating electrons that contribute to the current is spin-dependent. As the wave function phase depends upon the vector k, the closed path in the circuit produces spin-dependent current interference. This creates a physical scenario in which a spin-polarized current emerges, even in the absence of external magnetic fields or magnetic materials. It is possible to find points in the system's parameter space and, depending upon its geometry, the value of the Fermi energy and the spin-orbit intensities, for which the electronic states participating in the current have only one spin, creating a high and totally spin-polarized conductance. For a potential of a few tens of meV, it is possible to obtain a spin-polarized current of the order of μA. The properties of the obtained electronic current qualify the proposed device as a potentially important tool for spintronics applications.
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Affiliation(s)
- Victor Lopes
- Departamento de Física Aplicada, Universidad de Alicante, San Vicente del Raspeig, 03690 Alicante, Spain
| | - Guillermo Chiappe
- Departamento de Física Aplicada, Universidad de Alicante, San Vicente del Raspeig, 03690 Alicante, Spain
| | - Laercio C. Ribeiro
- Centro Federal de Educação Tecnológica Celso Suckow da Fonseca CEFET/RJ, Campus Nova Iguaçu, Nova Iguaçu, Rio de Janeiro 26041-271, Brazil
| | - Enrique V. Anda
- Departamento de Física, Pontifícia Universidade Católica do Rio de Janeiro (PUC-Rio), Rio de Janeiro 22451-900, Brazil
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Gruschwitz M, Ghosal C, Shen TH, Wolff S, Seyller T, Tegenkamp C. Surface Transport Properties of Pb-Intercalated Graphene. MATERIALS 2021; 14:ma14247706. [PMID: 34947298 PMCID: PMC8705698 DOI: 10.3390/ma14247706] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 12/06/2021] [Accepted: 12/09/2021] [Indexed: 11/26/2022]
Abstract
Intercalation experiments on epitaxial graphene are attracting a lot of attention at present as a tool to further boost the electronic properties of 2D graphene. In this work, we studied the intercalation of Pb using buffer layers on 6H-SiC(0001) by means of electron diffraction, scanning tunneling microscopy, photoelectron spectroscopy and in situ surface transport. Large-area intercalation of a few Pb monolayers succeeded via surface defects. The intercalated Pb forms a characteristic striped phase and leads to formation of almost charge neutral graphene in proximity to a Pb layer. The Pb intercalated layer consists of 2 ML and shows a strong structural corrugation. The epitaxial heterostructure provides an extremely high conductivity of σ=100 mS/□. However, at low temperatures (70 K), we found a metal-insulator transition that we assign to the formation of minigaps in epitaxial graphene, possibly induced by a static distortion of graphene following the corrugation of the interface layer.
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Li R. Searching strong 'spin'-orbit coupled one-dimensional hole gas in strong magnetic fields. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 34:075301. [PMID: 34753123 DOI: 10.1088/1361-648x/ac37da] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Accepted: 11/09/2021] [Indexed: 06/13/2023]
Abstract
We show that a strong 'spin'-orbit coupled one-dimensional hole gas is achievable via applying a strong magnetic field to the original two-fold degenerate (spin degeneracy) hole gas confined in a cylindrical Ge nanowire. Both strong longitudinal and strong transverse magnetic fields are feasible to achieve this goal. Based on quasi-degenerate perturbation calculations, we show the induced low-energy subband dispersion of the hole gas can be written asE=ℏ2kz2/(2mh*)+ασzkz+gh*μBBσx/2, a form exactly the same as that of the electron gas in the conduction band. Here the Pauli matricesσz,xrepresent a pseudo spin (or 'spin'), because the real spin degree of freedom has been split off from the subband dispersions by the strong magnetic field. Also, for a moderate nanowire radiusR= 10 nm, the induced effective hole massmh*(0.065∼0.08me)and the 'spin'-orbit couplingα(0.35 ∼ 0.8 eV Å) have a small magnetic field dependence in the studied magnetic field interval 1 <B< 15 T, while the effectiveg-factorgh*of the hole 'spin' only has a small magnetic field dependence in the large field region.
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Affiliation(s)
- Rui Li
- Key Laboratory for Microstructural Material Physics of Hebei Province, School of Science, Yanshan University, Qinhuangdao 066004, People's Republic of China
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Mamiyev Z, Fink C, Holtgrewe K, Pfnür H, Sanna S. Enforced Long-Range Order in 1D Wires by Coupling to Higher Dimensions. PHYSICAL REVIEW LETTERS 2021; 126:106101. [PMID: 33784116 DOI: 10.1103/physrevlett.126.106101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 01/23/2021] [Indexed: 06/12/2023]
Abstract
One-dimensional wires are known to be inherently unstable at finite temperature. Here, we show that long-range order of atomic Au double chains adsorbed on a Si(553) surface is not only stabilized by interaction with the substrate, but spontaneous self-healing of structural defects is actually enforced by the adsorption of atomic species such as Au or H. This is true even for random adsorbate distribution. Combining atomistic models within density functional theory with low energy electron diffraction and high-resolution electron energy loss spectroscopy, we demonstrate that this apparently counterintuitive behavior is mainly caused by adsorption-induced band filling of modified surface bands, i.e., by the strong electronic correlation throughout the whole terrace. Although adsorption preferably occurs at the step edge, it enhances the dimerization and the stiffness of the Au dimers. Thus, the intertwinement of quasi-1D properties with delocalized 2D effects enforces the atomic wire order.
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Affiliation(s)
- Zamin Mamiyev
- Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstraße 2, 30167 Hannover, Germany
- Laboratorium für Nano- und Quantenengineering (LNQE), Leibniz Universität Hannover, Schneiderberg 39, 30167 Hannover, Germany
- Institut für Physik, Technische Universität Chemnitz, Reichenhainer Straße 70, 09126 Chemnitz, Germany
| | - Christa Fink
- Institut für Theoretische Physik and Center for Materials Research (LaMa), Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, 35392 Gießen, Germany
| | - Kris Holtgrewe
- Institut für Theoretische Physik and Center for Materials Research (LaMa), Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, 35392 Gießen, Germany
| | - Herbert Pfnür
- Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstraße 2, 30167 Hannover, Germany
- Laboratorium für Nano- und Quantenengineering (LNQE), Leibniz Universität Hannover, Schneiderberg 39, 30167 Hannover, Germany
| | - Simone Sanna
- Institut für Theoretische Physik and Center for Materials Research (LaMa), Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 16, 35392 Gießen, Germany
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Hafke B, Brand C, Witte T, Sothmann B, Horn-von Hoegen M, Erwin SC. Thermally Induced Crossover from 2D to 1D Behavior in an Array of Atomic Wires: Silicon Dangling-Bond Solitons in Si(553)-Au. PHYSICAL REVIEW LETTERS 2020; 124:016102. [PMID: 31976688 DOI: 10.1103/physrevlett.124.016102] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Indexed: 06/10/2023]
Abstract
The self-assembly of submonolayer amounts of Au on the densely stepped Si(553) surface creates an array of closely spaced "atomic wires" separated by 1.5 nm. At low temperature, charge transfer between the terraces and the row of silicon dangling bonds at the step edges leads to a charge-ordered state within the row of dangling bonds with ×3 periodicity. Interactions between the dangling bonds lead to their ordering into a fully two-dimensional (2D) array with centered registry between adjacent steps. We show that as the temperature is raised, soliton defects are created within each step edge. The concentration of solitons rises with increasing temperature and eventually destroys the 2D order by decoupling the step edges, reducing the effective dimensionality of the system to 1D. This crossover from higher to lower dimensionality is unexpected and, indeed, opposite to the behavior in other systems.
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Affiliation(s)
- B Hafke
- Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen, 47057 Duisburg, Germany
| | - C Brand
- Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen, 47057 Duisburg, Germany
| | - T Witte
- Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen, 47057 Duisburg, Germany
| | - B Sothmann
- Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen, 47057 Duisburg, Germany
| | - M Horn-von Hoegen
- Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen, 47057 Duisburg, Germany
| | - S C Erwin
- Center for Computational Materials Science, Naval Research Laboratory, Washington, D.C. 20375, USA
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Lichtenstein T, Mamiyev Z, Jeckelmann E, Tegenkamp C, Pfnür H. Anisotropic 2D metallicity: plasmons in Ge(1 0 0)-Au. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:175001. [PMID: 30695765 DOI: 10.1088/1361-648x/ab02c5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The low-energy plasmonic excitations of the Ge(0 0 1)-Au close to one monolayer coverage of Au were investigated by momentum-resolved high resolution electron energy loss spectroscopy. A very weak plasmonic loss was identified dispersing along the chain direction of the [Formula: see text] formed at these Au coverages. The measured dispersion was compared with the Tomonaga-Luttinger-liquid (TLL) model and with a model for an anisotropic Fermi liquid. Using the TLL model both for single and arrays of wires, no consistent picture turned up that could describe all available data. On the contrary, a quasi-one-dimensional model of a confined 2D electron gas gave a satisfactorily consistent description of the data. From these results for the collective low-energy excitations we conclude that the Ge(0 0 1)-Au system is reasonably well described by a strongly anisotropic 2D Fermi liquid, but is incompatible with a TLL.
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Affiliation(s)
- T Lichtenstein
- Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstraße 2, 30167 Hannover, Germany
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Das T. Tuning directional dependent metal-insulator transitions in quasi-1D quantum wires with spin-orbit density wave instability. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:294001. [PMID: 27248294 DOI: 10.1088/0953-8984/28/29/294001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We study directional dependent band gap evolutions and metal-insulator transitions (MITs) in model quantum wire systems within the spin-orbit density wave (SODW) model. The evolution of MIT is studied as a function of varying anisotropy between the intra-wire hopping ([Formula: see text]) and inter-wire hopping ([Formula: see text]) with Rashba spin-orbit coupling. We find that as long as the anisotropy ratio ([Formula: see text]) remains below 0.5, and the Fermi surface nesting is tuned to [Formula: see text], an exotic SODW induced MIT easily develops, with its critical interaction strength increasing with increasing anisotropy. As [Formula: see text] (2D system), the nesting vector switches to [Formula: see text], making this state again suitable for an isotropic MIT. Finally, we discuss various physical consequences and possible applications of the directional dependent MIT.
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Affiliation(s)
- Tanmoy Das
- Department of Physics, Indian Institute of Physics, Bangalore-560012, India
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