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Rybkin AG, Tarasov AV, Rybkina AA, Usachov DY, Petukhov AE, Eryzhenkov AV, Pudikov DA, Gogina AA, Klimovskikh II, Di Santo G, Petaccia L, Varykhalov A, Shikin AM. Sublattice Ferrimagnetism in Quasifreestanding Graphene. PHYSICAL REVIEW LETTERS 2022; 129:226401. [PMID: 36493449 DOI: 10.1103/physrevlett.129.226401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 08/17/2022] [Accepted: 10/14/2022] [Indexed: 06/17/2023]
Abstract
We show that graphene can be magnetized by coupling to a ferromagnetic Co film through a Au monolayer. The presence of dislocation loops under graphene leads to a ferrimagnetic ordering of moments in the two C sublattices. It is shown that the band gap of ∼80 meV in the K[over ¯] point has a magnetic nature and exists for ferrimagnetic ordering. Interplay between Rashba and exchange couplings is evidenced by spin splitting asymmetry in spin-ARPES measurements and fully supported by DFT calculation of a (9×9) unit cell. Owing to sign-opposite Berry curvatures for K[over ¯] and K[over ¯]^{'} valleys, the synthesized system is promising for the realization of a circular dichroism Hall effect.
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Affiliation(s)
- Artem G Rybkin
- St. Petersburg State University, 198504 St. Petersburg, Russia
| | - Artem V Tarasov
- St. Petersburg State University, 198504 St. Petersburg, Russia
| | - Anna A Rybkina
- St. Petersburg State University, 198504 St. Petersburg, Russia
| | | | | | | | | | | | - Ilya I Klimovskikh
- St. Petersburg State University, 198504 St. Petersburg, Russia
- Center for Advanced Mesoscience and Nanotechnology, Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia
| | - Giovanni Di Santo
- Elettra Sincrotrone Trieste, Strada Statale 14 km 163.5, 34149 Trieste, Italy
| | - Luca Petaccia
- Elettra Sincrotrone Trieste, Strada Statale 14 km 163.5, 34149 Trieste, Italy
| | - Andrei Varykhalov
- Helmholtz-Zentrum Berlin für Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein-Str. 15, D-12489 Berlin, Germany
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Kochan D, Barth M, Costa A, Richter K, Fabian J. Spin Relaxation in s-Wave Superconductors in the Presence of Resonant Spin-Flip Scatterers. PHYSICAL REVIEW LETTERS 2020; 125:087001. [PMID: 32909806 DOI: 10.1103/physrevlett.125.087001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Revised: 05/22/2020] [Accepted: 07/22/2020] [Indexed: 06/11/2023]
Abstract
Employing analytical methods and quantum transport simulations we investigate the relaxation of quasiparticle spins in graphene proximitized by an s-wave superconductor in the presence of resonant magnetic and spin-orbit active impurities. Off resonance, the relaxation increases with decreasing temperature when electrons scatter off magnetic impurities-the Hebel-Slichter effect-and decreases when impurities have spin-orbit coupling. This distinct temperature dependence (not present in the normal state) uniquely discriminates between the two scattering mechanisms. However, we show that the Hebel-Slichter picture breaks down at resonances. The emergence of Yu-Shiba-Rusinov bound states within the superconducting gap redistributes the spectral weight away from magnetic resonances. The result is opposite to the Hebel-Slichter expectation: the spin relaxation decreases with decreasing temperature. Our findings hold for generic s-wave superconductors with resonant magnetic impurities, but also, as we show, for resonant magnetic Josephson junctions.
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Affiliation(s)
- Denis Kochan
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Michael Barth
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Andreas Costa
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Klaus Richter
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - Jaroslav Fabian
- Institute for Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
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Rybkina AA, Rybkin AG, Klimovskikh II, Skirdkov PN, Zvezdin KA, Zvezdin AK, Shikin AM. Advanced graphene recording device for spin-orbit torque magnetoresistive random access memory. NANOTECHNOLOGY 2020; 31:165201. [PMID: 31860886 DOI: 10.1088/1361-6528/ab6470] [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
The non-volatile spin-orbit torque magnetic random access memory (SOT-MRAM) is a very attractive memory technology for near future computers because it has various advantages such as non-volatility, high density and scalability. In the present work we propose a model of a graphene recording device for the SOT-MRAM unit cell, consisting of a quasi-freestanding graphene intercalated with Au and an ultra-thin Pt layer sandwiched between graphene and a magnetic tunnel junction. As a result of using the claimed graphene recording memory element, a faster operation and lower energy consumption will be achieved under the recording information by reducing the electric current required to record. The efficiency of the graphene recording element was confirmed by the experimental results and the theoretical estimations.
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Affiliation(s)
- A A Rybkina
- Saint Petersburg State University, Saint Petersburg, 198504 Russia
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Park J, Oh I, Jin MJ, Jo J, Choe D, Yun HD, Lee SW, Lee Z, Kwon SY, Jin H, Chung SB, Yoo JW. Observation of spin-polarized Anderson state around charge neutral point in graphene with Fe-clusters. Sci Rep 2020; 10:4784. [PMID: 32179819 PMCID: PMC7076017 DOI: 10.1038/s41598-020-61481-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Accepted: 02/17/2020] [Indexed: 11/09/2022] Open
Abstract
The pristine graphene described with massless Dirac fermion could bear topological insulator state and ferromagnetism via the band structure engineering with various adatoms and proximity effects from heterostructures. In particular, topological Anderson insulator state was theoretically predicted in tight-binding honeycomb lattice with Anderson disorder term. Here, we introduced physi-absorbed Fe-clusters/adatoms on graphene to impose exchange interaction and random lattice disorder, and we observed Anderson insulator state accompanying with Kondo effect and field-induced conducting state upon applying the magnetic field at around a charge neutral point. Furthermore, the emergence of the double peak of resistivity at ν = 0 state indicates spin-splitted edge state with high effective exchange field (>70 T). These phenomena suggest the appearance of topological Anderson insulator state triggered by the induced exchange field and disorder.
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Affiliation(s)
- Jungmin Park
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
- Center for Scientific Instrumentation, Division of Scientific Instrumentation & Management, Korea Basic Science Institute, Daejeon, 34133, Korea
| | - Inseon Oh
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
| | - Mi-Jin Jin
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
| | - Junhyeon Jo
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
| | - Daeseong Choe
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
| | - Hyung Duk Yun
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
| | - Suk Woo Lee
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
- Center for Multidimensional Carbon Materials, Institute for Basic Science (IBS), Ulsan, 44919, Republic of Korea
| | - Zonghoon Lee
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
- Center for Multidimensional Carbon Materials, Institute for Basic Science (IBS), Ulsan, 44919, Republic of Korea
| | - Soon-Yong Kwon
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea
| | - Hosub Jin
- Department of Physics, Ulsan National Institute of Science and Technology, Ulsan, 44919, Korea
| | - Suk Bum Chung
- Department of Physics, University of Seoul, Seoul, 02504, Korea
| | - Jung-Woo Yoo
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan, 44919, Republic of Korea.
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Vincent T, Voloshina E, Pons S, Simon S, Fonin M, Wang K, Paulus B, Roditchev D, Dedkov Y, Vlaic S. Quantum Well States for Graphene Spin-Texture Engineering. J Phys Chem Lett 2020; 11:1594-1600. [PMID: 32013453 DOI: 10.1021/acs.jpclett.0c00069] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The modification of graphene band structure, in particular via induced spin-orbit coupling, is currently a great challenge for the scientific community from both a fundamental and applied point of view. Here, we investigate the modification of the electronic structure of graphene (gr) initially adsorbed on Ir(111) via intercalation of one monolayer Pd by means of angle-resolved photoelectron spectroscopy and density functional theory. We reveal that for the gr/Pd/Ir(111) intercalated system, a spin splitting of graphene π states higher than 200 meV is present near the graphene K point. This spin separation arises from the hybridization of the graphene valence band states with spin-polarized quantum well states of a single Pd layer on Ir(111). Our results demonstrate that the proposed approach on the tailoring of the dimensionality of heavy materials interfaced with a graphene layer might lead to a giant spin-orbit splitting of the graphene valence band states.
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Affiliation(s)
- Thomas Vincent
- Laboratoire de Physique et d'Étude des Matériaux , ESPCI Paris, PSL Research University, CNRS, UMR 8213, Sorbonne Universités , UPMC Univ. Paris 06, 75005 Paris , France
| | - Elena Voloshina
- Department of Physics , Shanghai University , 99 Shangda Road , 200444 Shanghai , China
- Institut für Chemie und Biochemie , Freie Universität Berlin , Takustrasse 3 , 14195 Berlin , Germany
- Institute of Physical and Organic Chemistry , Southern Federal University , 344090 Rostov on Don , Russia
| | - Stéphane Pons
- Laboratoire de Physique et d'Étude des Matériaux , ESPCI Paris, PSL Research University, CNRS, UMR 8213, Sorbonne Universités , UPMC Univ. Paris 06, 75005 Paris , France
| | - Sabina Simon
- Department of Physics , University of Konstanz , 78457 Konstanz , Germany
| | - Mikhail Fonin
- Department of Physics , University of Konstanz , 78457 Konstanz , Germany
| | - Kangli Wang
- Institut für Chemie und Biochemie , Freie Universität Berlin , Takustrasse 3 , 14195 Berlin , Germany
| | - Beate Paulus
- Institut für Chemie und Biochemie , Freie Universität Berlin , Takustrasse 3 , 14195 Berlin , Germany
| | - Dimitri Roditchev
- Laboratoire de Physique et d'Étude des Matériaux , ESPCI Paris, PSL Research University, CNRS, UMR 8213, Sorbonne Universités , UPMC Univ. Paris 06, 75005 Paris , France
- INSP , UPMC Paris 6 and CNRS-UMR 7588, 4 place Jussieu , 75252 Paris , France
| | - Yuriy Dedkov
- Department of Physics , Shanghai University , 99 Shangda Road , 200444 Shanghai , China
- Institute of Physical and Organic Chemistry , Southern Federal University , 344090 Rostov on Don , Russia
| | - Sergio Vlaic
- Laboratoire de Physique et d'Étude des Matériaux , ESPCI Paris, PSL Research University, CNRS, UMR 8213, Sorbonne Universités , UPMC Univ. Paris 06, 75005 Paris , France
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Prediction and observation of an antiferromagnetic topological insulator. Nature 2019; 576:416-422. [PMID: 31853084 DOI: 10.1038/s41586-019-1840-9] [Citation(s) in RCA: 222] [Impact Index Per Article: 44.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Accepted: 09/18/2019] [Indexed: 11/08/2022]
Abstract
Magnetic topological insulators are narrow-gap semiconductor materials that combine non-trivial band topology and magnetic order1. Unlike their nonmagnetic counterparts, magnetic topological insulators may have some of the surfaces gapped, which enables a number of exotic phenomena that have potential applications in spintronics1, such as the quantum anomalous Hall effect2 and chiral Majorana fermions3. So far, magnetic topological insulators have only been created by means of doping nonmagnetic topological insulators with 3d transition-metal elements; however, such an approach leads to strongly inhomogeneous magnetic4 and electronic5 properties of these materials, restricting the observation of important effects to very low temperatures2,3. An intrinsic magnetic topological insulator-a stoichiometric well ordered magnetic compound-could be an ideal solution to these problems, but no such material has been observed so far. Here we predict by ab initio calculations and further confirm using various experimental techniques the realization of an antiferromagnetic topological insulator in the layered van der Waals compound MnBi2Te4. The antiferromagnetic ordering that MnBi2Te4 shows makes it invariant with respect to the combination of the time-reversal and primitive-lattice translation symmetries, giving rise to a ℤ2 topological classification; ℤ2 = 1 for MnBi2Te4, confirming its topologically nontrivial nature. Our experiments indicate that the symmetry-breaking (0001) surface of MnBi2Te4 exhibits a large bandgap in the topological surface state. We expect this property to eventually enable the observation of a number of fundamental phenomena, among them quantized magnetoelectric coupling6-8 and axion electrodynamics9,10. Other exotic phenomena could become accessible at much higher temperatures than those reached so far, such as the quantum anomalous Hall effect2 and chiral Majorana fermions3.
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Usachov DY, Bokai KA, Marchenko DE, Fedorov AV, Shevelev VO, Vilkov OY, Kataev EY, Yashina LV, Rühl E, Laubschat C, Vyalikh DV. Cobalt-assisted recrystallization and alignment of pure and doped graphene. NANOSCALE 2018; 10:12123-12132. [PMID: 29915820 DOI: 10.1039/c8nr03183e] [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
Recrystallization of bulk materials is a well-known phenomenon, which is widely used in commercial manufacturing. However, for low-dimensional materials like graphene, this process still remains an unresolved puzzle. Thus, the understanding of the underlying mechanisms and the required conditions for recrystallization in low dimensions is essential for the elaboration of routes towards the inexpensive and reliable production of high-quality nanomaterials. Here, we unveil the details of the efficient recrystallization of one-atom-thick pure and boron-doped polycrystalline graphene layers on a Co(0001) surface. By applying photoemission and electron diffraction, we show how more than 90% of the initially misoriented graphene grains can be reconstructed into a well-oriented and single-crystalline layer. The obtained recrystallized graphene/Co interface exhibits high structural quality with a pronounced sublattice asymmetry, which is important for achieving an unbalanced sublattice doping of graphene. By exploring the kinetics of recrystallization for native and B-doped graphene on Co, we were able to estimate the activation energy and propose a mechanism of this process.
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Affiliation(s)
- Dmitry Yu Usachov
- St. Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg, 199034, Russia.
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