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1تقرير
المؤلفون: Chekhov, A. L., Behovits, Y., Martens, U., Serrano, B. R., Wolf, M., Seifert, T. S., Muenzenberg, M., Kampfrath, T.
مصطلحات موضوعية: Physics - Optics
الوصف: We demonstrate detection of broadband intense terahertz electromagnetic pulses by Zeeman-torque sampling (ZTS). Our approach is based on magneto-optic probing of the Zeeman torque the terahertz magnetic field exerts on the magnetization of a ferromagnet. Using an 8 nm thick iron film as sensor, we detect pulses from a silicon-based spintronic terahertz emitter with bandwidth 0.1-11 THz and peak field >0.1 MV/cm. Static calibration provides access to absolute transient THz field strengths. We show relevant added values of ZTS compared to electro-optic sampling (EOS): an absolute and echo-free transfer function with simple frequency dependence, linearity even at high terahertz field amplitudes, the straightforward calibration of EOS response functions and the modulation of the polarization-sensitive direction by an external AC magnetic field. Consequently, ZTS has interesting applications even beyond the accurate characterization of broadband high-field terahertz pulses for nonlinear terahertz spectroscopy.
الوصول الحر: http://arxiv.org/abs/2306.09734Test
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2تقرير
المؤلفون: Rouzegar, R., Wahada, M. A., Chekhov, A. L., Hoppe, W., Jechumtal, J., Nadvornik, L., Wolf, M., Seifert, T. S., Parkin, S. S. P., Woltersdorf, G., Brouwer, P. W., Kampfrath, T.
مصطلحات موضوعية: Physics - Applied Physics, Condensed Matter - Mesoscale and Nanoscale Physics
الوصف: We study femtosecond spin currents through MgO tunneling barriers in CoFeB(2 nm)|MgO($d$)|Pt(2 nm) stacks by terahertz emission spectroscopy. To obtain transport information independent of extrinsic experimental factors, we determine the complex-valued spin conductance $\tilde{G}_d (\omega)$ of the MgO layer (thickness d= 0-6 {\AA} over a wide frequency range $(\omega/2\pi=$ 0.5-8 THz). In the time $(t)$ domain,$ G_d (t)$ has an instantaneous and delayed component that point to (i) spin transport through Pt pinholes in MgO, (ii) coherent spin tunneling and (iii) incoherent resonant spin tunneling mediated by defect states in MgO. A remarkable signature of (iii) is its relaxation time that grows monotonically with $d$ to as much as 270 fs at $d= 6$ {\AA}, in full agreement with an analytical model. Our results indicate that terahertz spin conductance spectroscopy will yield new and relevant insights into ultrafast spin transport for a wide range of materials.
Comment: 4 figuresالوصول الحر: http://arxiv.org/abs/2305.09074Test
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3تقرير
المؤلفون: Rongione, E., Gueckstock, O., Mattern, M., Gomonay, O., Meer, H., Schmitt, C., Ramos, R., Saitoh, E., Sinova, J., Jaffrès, H., Mičica, M., Mangeney, J., Goennenwein, S. T. B., Geprägs, S., Kampfrath, T., Kläui, M., Bargheer, M., Seifert, T. S., Dhillon, S., Lebrun, R.
مصطلحات موضوعية: Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Other Condensed Matter, Physics - Optics
الوصف: Antiferromagnetic materials have been proposed as new types of narrowband THz spintronic devices owing to their ultrafast spin dynamics. Manipulating coherently their spin dynamics, however, remains a key challenge that is envisioned to be accomplished by spin-orbit torques or direct optical excitations. Here, we demonstrate the combined generation of broadband THz (incoherent) magnons and narrowband (coherent) magnons at 1 THz in low damping thin films of NiO/Pt. We evidence, experimentally and through modelling, two excitation processes of magnetization dynamics in NiO, an off-resonant instantaneous optical spin torque and a strain-wave-induced THz torque induced by ultrafast Pt excitation. Both phenomena lead to the emission of a THz signal through the inverse spin Hall effect in the adjacent heavy metal layer. We unravel the characteristic timescales of the two excitation processes found to be < 50 fs and > 300 fs, respectively, and thus open new routes towards the development of fast opto-spintronic devices based on antiferromagnetic materials.
الوصول الحر: http://arxiv.org/abs/2205.11965Test
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4تقرير
المؤلفون: Schumann, T., Kleinke, T., Braun, L., Meyer, N., Mussler, G., Kampmeier, J., Grützmacher, D., Schmoranzerova, E., Olejník, K., Reichlová, H., Heiliger, C., Denker, C., Walowski, J., Kampfrath, T., Münzenberg, M.
مصطلحات موضوعية: Condensed Matter - Mesoscale and Nanoscale Physics
الوصف: We study laser driven spin-current effects at ferromagnet/topological-insulator interfaces by two complementary experimental approaches. The DC photocurrent is studied in ferromagnet/topological-insulator bilayers with high spatial resolution. Dynamic interface currents are explored via the emission of terahertz radiation emitted by these currents with high temporal resolution. From our experiments, we reveal a lateral and dynamic interaction of the ferromagnet and the topological insulator interface.
Comment: 15 pages,5 figuresالوصول الحر: http://arxiv.org/abs/2202.01522Test
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5تقرير
المؤلفون: Heitz, J. J. F., Nádvorník, L., Balos, V., Behovits, Y., Chekhov, A. L., Seifert, T. S., Olejník, K., Kašpar, Z., Geishendorf, K., Novák, V., Campion, R. P., Wolf, M., Jungwirth, T., Kampfrath, T.
مصطلحات موضوعية: Physics - Applied Physics, Condensed Matter - Mesoscale and Nanoscale Physics
الوصف: We show scalable and complete suppression of the recently reported terahertz-pulse-induced switching between different resistance states of antiferromagnetic CuMnAs thin films by ultrafast gating. The gating functionality is achieved by an optically generated transiently conductive parallel channel in the semiconducting substrate underneath the metallic layer. The photocarrier lifetime determines the time scale of the suppression. As we do not observe a direct impact of the optical pulse on the state of CuMnAs, all observed effects are primarily mediated by the substrate. The sample region of suppressed resistance switching is given by the optical spot size, thereby making our scheme potentially applicable for transient low-power masking of structured areas with feature sizes of ~100 nm and even smaller.
الوصول الحر: http://arxiv.org/abs/2106.08828Test
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6تقرير
المؤلفون: Chekhov, A. L., Behovits, Y., Heitz, J. J. F., Denker, C., Reiss, D. A., Wolf, M., Weinelt, M., Brouwer, P. W., Münzenberg, M., Kampfrath, T.
مصطلحات موضوعية: Physics - Optics
الوصف: We study ultrafast magnetization quenching of ferromagnetic iron following excitation by an optical vs a terahertz pump pulse. While the optical pump (photon energy of 3.1 eV) induces a strongly nonthermal electron distribution, terahertz excitation (~4 meV) results in a quasi-thermal perturbation of the electron population. The pump-induced spin and electron dynamics are interrogated by the magneto-optic Kerr effect (MOKE). A deconvolution procedure allows us to push the time resolution down to 130 fs, even though the driving terahertz pulse is more than 0.5 ps long. Remarkably, the MOKE signals exhibit an almost identical time evolution for both optical and terahertz pump pulses, despite the three orders of magnitude different number of excited electrons. We are able to quantitatively explain our results using a model based on quasi-elastic spin-flip scattering. It shows that in the small-perturbation limit, the rate of demagnetization of a metallic ferromagnet is proportional to the excess energy of the electrons, independent of the precise shape of their distribution. Our results reveal that the dynamics of ultrafast demagnetization and of the closely related terahertz spin transport do not depend on the pump photon energy.
Comment: 10 pages, 5 figures, Supplemental material includedالوصول الحر: http://arxiv.org/abs/2106.01967Test
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7دورية أكاديمية
المؤلفون: Leitenstorfer, A, Moskalenko, AS, Kampfrath, T, Kono, J, Castro-Camus, E, Peng, K, Qureshi, N, Turchinovich, D, Tanaka, K, Markelz, AG, Havenith, M, Hough, C, Joyce, HJ, Padilla, WJ, Zhou, B, Kim, K-Y, Zhang, X-C, Jepsen, PU, Dhillon, S, Vitiello, M, Linfield, E, Davies, AG, Hoffmann, MC, Lewis, R, Tonouchi, M, Klarskov, P, Seifert, TS, Gerasimenko, YA, Mihailovic, D, Huber, R, Boland, JL, Mitrofanov, O, Dean, P, Ellison, BN, Huggard, PG, Rea, SP, Walker, C, Leisawitz, DT, Gao, JR, Li, C, Chen, Q, Valusis, G, Wallace, VP, Pickwell-MacPherson, E, Shang, X, Hesler, J, Ridler, N, Renaud, CC, Kallfass, I, Johnston, MB, Nagatsuma, T
الوصف: Terahertz (THz) radiation encompasses a wide spectral range within the electromagnetic spectrum that extends from microwaves to the far infrared (100 GHz-∼30 THz). Within its frequency boundaries exist a broad variety of scientific disciplines that have presented, and continue to present, technical challenges to researchers. During the past 50 years, for instance, the demands of the scientific community have substantially evolved and with a need for advanced instrumentation to support radio astronomy, Earth observation, weather forecasting, security imaging, telecommunications, non-destructive device testing and much more. Furthermore, applications have required an emergence of technology from the laboratory environment to production-scale supply and in-the-field deployments ranging from harsh ground-based locations to deep space. In addressing these requirements, the research and development community has advanced related technology and bridged the transition between electronics and photonics that high frequency operation demands. The multidisciplinary nature of THz work was our stimulus for creating the 2017 THz Science and Technology Roadmap (Dhillon et al 2017 J. Phys. D: Appl. Phys. 50 043001). As one might envisage, though, there remains much to explore both scientifically and technically and the field has continued to develop and expand rapidly. It is timely, therefore, to revise our previous roadmap and in this 2023 version we both provide an update on key developments in established technical areas that have important scientific and public benefit, and highlight new and emerging areas that show particular promise. The developments that we describe thus span from fundamental scientific research, such as THz astronomy and the emergent area of THz quantum optics, to highly applied and commercially and societally impactful subjects that include 6G THz communications, medical imaging, and climate monitoring and prediction. Our Roadmap vision draws upon the expertise and perspective of multiple international ...
العلاقة: https://ora.ox.ac.uk/objects/uuid:48cc5b6f-62a2-4ef2-a417-bfec68dd2b87Test; https://doi.org/10.1088/1361-6463/acbe4cTest
الإتاحة: https://doi.org/10.1088/1361-6463/acbe4cTest
https://ora.ox.ac.uk/objects/uuid:48cc5b6f-62a2-4ef2-a417-bfec68dd2b87Test -
8دورية أكاديمية
المؤلفون: Gückstock, O., Stojanovic, N., Ha, Y., Hagelschuer, T., Denker, A., Kourkafas, G., Seifert, T., Kampfrath, T., Gensch, M.
المصدر: Applied Physics Letters
الوصف: The radiation hardness of ultrabroadband, spintronic terahertz emitters against gamma and proton irradiation is investigated. We find that irradiation doses equivalent to those experienced by a space instrument en-route to and operated on Mars have a minor effect on the performance of the emitter. In particular, the ultrawide emission spectrum 0.1-30 THz, which covers a large part of the vibrational fingerprint region, remains unchanged. These results make this emitter type highly interesting as essential building block for broad-band gas sensors based on terahertz time-domain spectroscopy for future space missions.
وصف الملف: application/pdf
العلاقة: info:eu-repo/semantics/altIdentifier/arxiv/2401.10672; http://hdl.handle.net/21.11116/0000-000E-7002-1Test; http://hdl.handle.net/21.11116/0000-000E-7004-FTest; http://hdl.handle.net/21.11116/0000-000F-2161-ETest
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9دورية أكاديمية
المؤلفون: Frenzel, M., Urban, J., Nest, L., Kampfrath, T., Spencer, M., Maehrlein, S.
المصدر: Optica
الوصف: The advent of high-field THz sources has opened the field of nonlinear THz physics and unlocked access to fundamental low energy excitations for ultrafast material control. Recent advances towards controlling and employing chiral excitations, or generally angular momentum of light, not only rely on the measurement of undistorted intense THz fields, but also on the precise knowledge about sophisticated THz helicity states. A recently reported and promising detector material is α-quartz. However, its electrooptic response function and contributing nonlinear effects have remained elusive. Here, we establish z-cut α-quartz as a precise electrooptic THz detector for full amplitude, phase and polarization measurement of intense THz fields, all at a fraction of costs of conventional THz detectors. We experimentally determine its complex detector response function, which is in good agreement with our model based on predominantly known literature values. It also explains previously observed thickness-dependent waveforms. These insights allow us to develop a swift and reliable protocol to precisely measure arbitrary THz polarization and helicity states. This two-dimensional electrooptic sampling (2D-EOS) in α-quartz fosters rapid and cost-efficient THz time-domain ellipsometry, and enables the characterization of polarization-tailored fields for driving chiral or other helicity-sensitive quasiparticles and topologies.
وصف الملف: application/pdf
العلاقة: info:eu-repo/semantics/altIdentifier/arxiv/2309.08286; http://hdl.handle.net/21.11116/0000-000E-5214-FTest; http://hdl.handle.net/21.11116/0000-000E-5216-DTest; http://hdl.handle.net/21.11116/0000-000F-2137-ETest
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10تقرير
المؤلفون: Rouzegar, R., Brandt, L., Nadvornik, L., Reiss, D. A., Chekhov, A. L., Gueckstock, O., In, C., Wolf, M., Seifert, T. S., Brouwer, P. W., Woltersdorf, G., Kampfrath, T.
مصطلحات موضوعية: Condensed Matter - Mesoscale and Nanoscale Physics
الوصف: Laser-induced terahertz spin transport (TST) and ultrafast demagnetization (UDM) are central but so far disconnected phenomena in femtomagnetism and terahertz spintronics. Here, we use broadband terahertz emission spectroscopy to reliably measure both processes in one setup. We find that the rate of UDM of a single ferromagnetic metal film F has the same time evolution as the flux of TST from F into an adjacent normal-metal layer N. This remarkable agreement shows that UDM and TST are driven by the same force, which is fully determined by the state of the ferromagnet. An analytical model consistently and quantitatively explains our observations. It reveals that both UDM in F and TST in the F|N stack arise from a generalized spin voltage, which is defined for arbitrary, nonthermal electron distributions. We also conclude that contributions due to a possible temperature difference between F and N are minor and that the spin-current amplitude can, in principle, be increased by one order of magnitude. In general, our findings allow one to apply the vast knowledge of UDM to TST, thereby opening up new pathways toward large-amplitude terahertz spin currents and, thus, energy-efficient ultrafast spintronic devices.
Comment: 23 pagesالوصول الحر: http://arxiv.org/abs/2103.11710Test
