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Mishra SS, Lourembam J, Lin DJX, Singh R. Active ballistic orbital transport in Ni/Pt heterostructure. Nat Commun 2024; 15:4568. [PMID: 38811558 PMCID: PMC11137139 DOI: 10.1038/s41467-024-48891-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Accepted: 05/15/2024] [Indexed: 05/31/2024] Open
Abstract
Orbital current, defined as the orbital character of Bloch states in solids, can travel with larger coherence length through a broader range of materials than its spin counterpart, facilitating a robust, higher density and energy efficient information transmission. Hence, active control of orbital transport plays a pivotal role in the progress of the evolving field of quantum information technology. Unlike spin angular momentum, orbital angular momentum couples to phonon angular momentum efficiently via orbital-crystal momentum (L-k) coupling, allowing us to control orbital transport through crystal field potential mediated angular momentum transfer. Here, leveraging the orbital dependant efficient L-k coupling, we have experimentally demonstrated the active control of orbital current velocity in Ni/Pt heterostructure. We observe terahertz emission from Ni/Pt heterostructure via long-range ballistic orbital transport, as evidenced by the delay, and chirping in the emitted THz pulse correlating with increased Pt thickness. Additionally, we also have identified a critical energy density required to overcome collisions in orbital transport, enabling a swifter flow of orbital current. Femtosecond light driven active control of the ballistic orbital transport lays the foundation for the development of dynamic optorbitronics for transmitting information over extended distance.
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Affiliation(s)
- Sobhan Subhra Mishra
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
- Centre for Disruptive Photonic Technologies, The Photonics Institute, Nanyang Technological University, Singapore, 639798, Singapore
| | - James Lourembam
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 2 Fusionopolis Way, Singapore, 138364, Singapore
| | - Dennis Jing Xiong Lin
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research, 2 Fusionopolis Way, Singapore, 138364, Singapore
| | - Ranjan Singh
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore.
- Centre for Disruptive Photonic Technologies, The Photonics Institute, Nanyang Technological University, Singapore, 639798, Singapore.
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Yadav P, Xinhou C, Bhatt S, Das S, Yang H, Mishra R. Highly Efficient Spintronic Terahertz Emitter Utilizing a Large Spin Hall Conductivity of Type-II Dirac Semimetal PtTe 2. NANO LETTERS 2024; 24:2376-2383. [PMID: 38329912 DOI: 10.1021/acs.nanolett.3c04986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2024]
Abstract
The remarkable spin-charge interconversion ability of transition metal dichalcogenides (TMDs) makes them promising candidates for spintronic applications. Nevertheless, their potential as spintronic terahertz (THz) emitters (STEs) remains constrained mainly due to their sizable resistivity and low spin Hall conductivity (SHC), which consequently result in modest THz emission. In this work, the TMD PtTe2, a type-II Dirac semimetal is effectively utilized to develop efficient STEs. This high efficiency primarily results from the large SHC of PtTe2, stemming from its low resistivity and significant spin-to-charge conversion efficiency, attributed to surface states and the local Rashba effect in addition to the inverse spin Hall effect. Remarkably, the peak THz emission from PtTe2/Co-STE exceeds that of Pt/Co-STE by ∼15% and is nearly double that of a similarly thick Pt/Co-STE. The efficient THz emission in the PtTe2/Co heterostructure opens new possibilities for utilizing the semimetal TMDs for developing THz emitters.
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Affiliation(s)
- Pinki Yadav
- Center for Applied Research in Electronics, Indian Institute of Technology Delhi, Delhi 110016, India
| | - Chen Xinhou
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576
| | - Shubham Bhatt
- Center for Applied Research in Electronics, Indian Institute of Technology Delhi, Delhi 110016, India
| | - Samaresh Das
- Center for Applied Research in Electronics, Indian Institute of Technology Delhi, Delhi 110016, India
| | - Hyunsoo Yang
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576
| | - Rahul Mishra
- Center for Applied Research in Electronics, Indian Institute of Technology Delhi, Delhi 110016, India
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Ziolkowski F, Busch O, Mertig I, Henk J. Ultrafast spin dynamics: complementing theoretical analyses by quantum state measures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2023; 35:125501. [PMID: 36652715 DOI: 10.1088/1361-648x/acb479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Accepted: 01/18/2023] [Indexed: 06/17/2023]
Abstract
In theoretical analyses of ultrafast spin dynamics simulated phenomena are commonly discussed in terms of observables. In this paper we report on possible benefits of complementing such studies by quantum state (QS) measures. These measures quantify specific properties of QSs, e.g. distance in Hilbert space and mixing. For Co/Cu heterostructures illuminated by femtosecond laser pulses, we discuss the general behavior of selected measures, but address in particular the degree of perturbation by a laser pulse. It turns out that the measures are especially sensitive to variations of the polarization of a laser pulse and the sample composition. Moreover, they are closely linked to magnetization and number of photo-excited electrons.
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Affiliation(s)
- Franziska Ziolkowski
- Institut für Physik, Martin Luther University Halle-Wittenberg, 06099 Halle, Germany
| | - Oliver Busch
- Institut für Physik, Martin Luther University Halle-Wittenberg, 06099 Halle, Germany
| | - Ingrid Mertig
- Institut für Physik, Martin Luther University Halle-Wittenberg, 06099 Halle, Germany
| | - Jürgen Henk
- Institut für Physik, Martin Luther University Halle-Wittenberg, 06099 Halle, Germany
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Mag-usara VK, Escaño MC, Petoukhoff CE, Torosyan G, Scheuer L, Madéo J, Afalla J, Talara ML, Muldera JE, Kitahara H, Bacon DR, Nakajima M, Dani K, Papaioannou ET, Beigang R, Tani M. Optimum excitation wavelength and photon energy threshold for spintronic terahertz emission from Fe/Pt bilayer. iScience 2022; 25:104615. [PMID: 35800756 PMCID: PMC9253697 DOI: 10.1016/j.isci.2022.104615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 05/25/2022] [Accepted: 06/10/2022] [Indexed: 11/29/2022] Open
Abstract
Terahertz emission from ferromagnetic/non-magnetic spintronic heterostructures had been demonstrated as pump wavelength-independent. We report, however, the pump wavelength dependence of terahertz emission from an optimized Fe/Pt spintronic bilayer on MgO substrate. Maximum terahertz generation per total pump power was observed in the 1200- to 1800-nm pump wavelength range, and a marked decrease in the terahertz emission efficiency beyond 2500 nm (pump photon energies <0.5 eV) suggests a ∼0.35-eV threshold pump photon energy for effective spintronic terahertz emission. The inferred threshold is supported by previous theoretical results on the onset energy of significant spin-filtering at the Fe-Pt interface, and confirmed by Fe/Pt electronic structure calculations in this present work. The results of terahertz time-domain emission spectroscopy show the sensitivity of spintronic terahertz emission to both the optical absorptance of the heterostructure and the energy-dependent spin transport, as dictated by the properties of the metallic thin films. Excitation wavelength dependence of THz emission from spintronic Fe/Pt bilayer Maximum THz emission efficiency of Fe/Pt in the 1200 to 1800-nm pump wavelength range Inferred pump photon energy threshold linked to spin-filtering at the Fe-Pt interface Effect of pump absorptance and energy-dependent spin transport on Fe/Pt THz emission
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Scheuer L, Ruhwedel M, Karfaridis D, Vasileiadis IG, Sokoluk D, Torosyan G, Vourlias G, Dimitrakopoulos GP, Rahm M, Hillebrands B, Kehagias T, Beigang R, Papaioannou ET. THz emission from Fe/Pt spintronic emitters with L1 0-FePt alloyed interface. iScience 2022; 25:104319. [PMID: 35602944 PMCID: PMC9114522 DOI: 10.1016/j.isci.2022.104319] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Revised: 03/28/2022] [Accepted: 04/25/2022] [Indexed: 11/02/2022] Open
Abstract
Recent developments in nanomagnetism and spintronics have enabled the use of ultrafast spin physics for terahertz (THz) emission. Spintronic THz emitters, consisting of ferromagnetic (FM)/non-magnetic (NM) thin film heterostructures, have demonstrated impressive properties for the use in THz spectroscopy and have great potential in scientific and industrial applications. In this work, we focus on the impact of the FM/NM interface on the THz emission by investigating Fe/Pt bilayers with engineered interfaces. In particular, we intentionally modify the Fe/Pt interface by inserting an ordered L10-FePt alloy interlayer. Subsequently, we establish that a Fe/L10-FePt (2 nm)/Pt configuration is significantly superior to a Fe/Pt bilayer structure, regarding THz emission amplitude. The latter depends on the extent of alloying on either side of the interface. The unique trilayer structure opens new perspectives in terms of material choices for the next generation of spintronic THz emitters.
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Affiliation(s)
- Laura Scheuer
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, Kaiserslautern 67663, Germany
| | - Moritz Ruhwedel
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, Kaiserslautern 67663, Germany
| | - Dimitrios Karfaridis
- Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece
| | - Isaak G Vasileiadis
- Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece
| | - Dominik Sokoluk
- Fachbereich Elektro-Informationstechnik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, Kaiserslautern 67663, Germany
| | - Garik Torosyan
- Photonic Center Kaiserslautern, Kaiserslautern 67663, Germany
| | - George Vourlias
- Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece
| | | | - Marco Rahm
- Fachbereich Elektro-Informationstechnik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, Kaiserslautern 67663, Germany
| | - Burkard Hillebrands
- Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, Kaiserslautern 67663, Germany
| | - Thomas Kehagias
- Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece
| | - René Beigang
- Fachbereich Physik, Technische Universität Kaiserslautern, Kaiserslautern 67663, Germany
| | - Evangelos Th Papaioannou
- Institut für Physik, Martin-Luther Universität Halle Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle, Germany
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Kumar S, Nivedan A, Singh A, Kumar Y, Malhotra P, Tondusson M, Freysz E, Kumar S. Optical damage limit of efficient spintronic THz emitters. iScience 2021; 24:103152. [PMID: 34646990 PMCID: PMC8496183 DOI: 10.1016/j.isci.2021.103152] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2021] [Revised: 08/25/2021] [Accepted: 09/16/2021] [Indexed: 11/04/2022] Open
Abstract
THz pulses are generated from femtosecond pulse-excited ferromagnetic/nonmagnetic spintronic heterostructures via inverse spin Hall effect. The highest possible THz signal strength from spintronic THz emitters is limited by the optical damage threshold of the corresponding heterostructures at the excitation wavelength. For the thickness-optimized spintronic heterostructure, the THz generation efficiency does not saturate with the excitation fluence even up till the damage threshold. Bilayer (Fe, CoFeB)/(Pt, Ta)-based ferromagnetic/nonmagnetic (FM/NM) spintronic heterostructures have been studied for an optimized performance for THz generation when pumped by sub-50 fs amplified laser pulses at 800 nm. Among them, CoFeB/Pt is the best combination for an efficient THz source. The optimized FM/NM spintronic heterostructure having α-phase Ta as the nonmagnetic layer shows the highest damage threshold as compared to those with Pt, irrespective of their generation efficiency. The damage threshold of the Fe/Ta heterostructure on a quartz substrate is ∼85 GW/cm2. THz generation efficiency of (CoFeB,Fe)/(Pt,Ta) spintronic film heterostructures Determination of optical damage threshold at NIR excitation Mean value of the optical damage threshold is ∼60 GW/cm2
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Affiliation(s)
- Sandeep Kumar
- Femtosecond Spectroscopy and Nonlinear Photonics Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
| | - Anand Nivedan
- Femtosecond Spectroscopy and Nonlinear Photonics Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
| | - Arvind Singh
- Femtosecond Spectroscopy and Nonlinear Photonics Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
| | - Yogesh Kumar
- Laser Science and Technology Center, Metcalfe House, Civil Lines, New Delhi 110054, India
| | - Purnima Malhotra
- Laser Science and Technology Center, Metcalfe House, Civil Lines, New Delhi 110054, India
| | - Marc Tondusson
- Univ. Bordeaux, CNRS, LOMA, UMR 5798, 33405 Talence, France
| | - Eric Freysz
- Univ. Bordeaux, CNRS, LOMA, UMR 5798, 33405 Talence, France
| | - Sunil Kumar
- Femtosecond Spectroscopy and Nonlinear Photonics Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
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Modification of spintronic terahertz emitter performance through defect engineering. Sci Rep 2019; 9:13348. [PMID: 31527771 PMCID: PMC6746872 DOI: 10.1038/s41598-019-49963-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Accepted: 09/03/2019] [Indexed: 11/08/2022] Open
Abstract
Spintronic ferromagnetic/non-magnetic heterostructures are novel sources for the generation of THz radiation based on spin-to-charge conversion in the layers. The key technological and scientific challenge of THz spintronic emitters is to increase their intensity and frequency bandwidth. Our work reveals the factors to engineer spintronic Terahertz generation by introducing the scattering lifetime and the interface transmission for spin polarized, non-equilibrium electrons. We clarify the influence of the electron-defect scattering lifetime on the spectral shape and the interface transmission on the THz amplitude, and how this is linked to structural defects of bilayer emitters. The results of our study define a roadmap of the properties of emitted as well as detected THz-pulse shapes and spectra that is essential for future applications of metallic spintronic THz emitters.
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Visible Measurement of Terahertz Power Based on Capsulized Cholesteric Liquid Crystal Film. APPLIED SCIENCES-BASEL 2018. [DOI: 10.3390/app8122580] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We demonstrate a new method to detect terahertz (THz) power using a temperature-supersensitive capsulized cholesteric liquid crystal film based on the thermochromic and thermodiffusion effect, which is clearly observed. A quantitative visualization of the THz intensity up to 4.0 × 103 mW/cm2 is presented. The diameter of the color change area is linearly dependent on the THz radiation power above 0.07 mW in the steady state. Moreover, the THz power can be detected for 1 sec of radiation with a parabolic relation to the color change area. The THz power meter is robust, cost-effective, portable, and even flexible, and can be used in applications such as THz imaging, biological sensing, and inspection.
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