Intrinsische Josephsonkontakte aus Bi2Sr2CaCu2O8 als kohärente THz-Emitter
Zusammenfassung der Projektergebnisse
Electromagnetic radiation at frequencies in the terahertz (THz) range is highly interesting for applications, however, particularly the frequency range between 0.5 and 1.5 THz has turned out to be difficult to fill with powerful coherent solid-state sources. Stacks of intrinsic Josephson junctions (IJJs) made of the high temperature superconductor Bi2Sr2CaCu2O8 (BSCCO) operate in this regime. In general, the overall figures of merits, in terms of for emission power (some ten µW for a single stack, up to 0.6 mW for an array of stacks) and frequency (between 0.4 and 2.4 THz) and the linewidth of radiation (down to a few MHz), of BSCCO based THz oscillators look very promising. However, nobody succeeded yet in combining them in one and the same device. Often, one faces irreproducibility and there is the lack of an overall understanding of the device physics and the strategy to build an optimized oscillator. These issues motivated the present project. The research was performed in close collaboration between the groups of H. B. Wang (RISE, Nanjing), V. P. Koshelets (IREE, Moscow) and R. Kleiner (Tübingen). The project had three main goals. The first one was to improve our understanding of the mechanism of THz generation in IJJ stacks. There is consensus now that electromagnetic resonances utilizing the whole stack as a cavity are essential for synchronization. In addition, at sufficiently high bias currents ("high bias regime"), Joule heating leads to the formation of hotspots - local regions heated to temperatures above the superconducting transition temperature - inside the stack. The hotspots take part in the synchronization process and seem to lead to a highly narrowed linewidth of radiation compared to the low-bias regime where the hotspot is absent. Shining more light on these processes was in the heart of goal 1. The second goal was to use arrays of IJJ stacks to increase the emission power and to decrease the linewidth of radiation further. The main motivation for goal 2 arises from the fact that severe Joule heating prevents that the number of IJJs in single single stacks is increased much further. The third goal was to give demonstrations of applications, e. g. in terms of spectroscopy. For goal 1 a major step was the development of a numerical code to simulate stacks of a realistic size, taking into account electrodynamics as well as Joule heating. Such a code was under construction and now further improved and applied to experimental data. The code works reproduces many, although not all properties of the BSCCO THz emitters. It is used now as a routine tool to simulate IJJ stacks and provides a deeper understanding of the complex physics of these emitters. With respect to goal 2 pre-investigations indicated that IJJ stacks should be coupled by a common BSCCO base crystal to provide mutual coupling. By contrast, it actually turned out, that a common gold electrode is sufficient to provide coupling even if the stacks are located at a relatively large distance. The mutual coupling between two stacks was achieved. The possibility to couple stacks by the Au electrode over substantial distances to strongly relax the Joule heating problem. In terms of goal 3 we demonstrated that gas detection at THz frequencies can be performed using BSCCO THz emitters. Two different setups were used. The first is a very simple one where the emitter was mounted on a Stirling cryocooler (end temperature 30 K) while for the detection a Golay cell was used. In the second, more sophisticated, setup an all-superconducting receiver and a hererodyne scheme was used for detection and the BSCCO emitter was operated at 4.2 K. Both setups worked excellently. Their performance is not so different from quantum-cascade-laser-based schemes realized for gas sensing in the 2- to 3-THz range. BSCCO emitters are suitable candidates for THz spectroscopy for frequencies of between about 0.4 and 2 THz and can be used for applications in environmental monitoring.
Projektbezogene Publikationen (Auswahl)
- 3D simulations of the electrothermal and THz emission properties of Bi2Sr2CaCu2O8 intrinsic Josephson junction stacks. Phys. Rev. Appl. 5, 044017 (2016)
F. Rudau, R. Wieland, J. Langer, N. Kinev, J. Yuan, Y. Huang, M. Ji, X.J. Zhou, A. Ishii, P. H. Wu, T. Hatano, H. B. Wang, V. P. Koshelets, D. Koelle, R. Kleiner
(Siehe online unter https://doi.org/10.1103/PhysRevApplied.5.044017) - Modulating the emission properties of superconducting terahertz emitters. Terahertz Science and Technology 9, 60 (2016)
X. J. Zhou, M. Ji, D. Y. An, F. Rudau, R. Wieland, Q. Zhu, H. C. Sun, L. Y. Hao, D. Koelle, R. Kleiner, H. B. Wang, P. H. Wu
- Bi2Sr2CaCu2O8 intrinsic Josephson junction stacks as emitters of terahertz radiation. Chapter 12 in Superconductors at the Nanoscale, R. Wördenweber, V. Moshchalkov, S. Bending, F. Tafuri (eds), de Gruyter (2017)
R. Kleiner and H.-B. Wang
(Siehe online unter https://doi.org/10.1515/9783110456806-013) - Self-mixing spectra of terahertz emitters based on Bi2Sr2CaCu2O8+δ intrinsic Josephson junction stacks. Phys. Rev. Applied 8, 054023 (2017)
Y. Huang, H. Sun, D. An, X. Zhou, M. Ji, F. Rudau, R. Wieland, J. S. Hampp, O. Kizilaslan, J. Yuan, N. Kinev, O. Kiselev, V. P. Koshelets, J. Li, D. Koelle, R. Kleiner, B. Jin, J. Chen, L. Kang, W. Xu, H.-B. Wang, P. Wu
(Siehe online unter https://doi.org/10.1103/PhysRevApplied.8.054023) - Terahertz spectroscopy of dilute gases using Bi2Sr2CaCu2O8+δ intrinsic Josephson junction stacks. Phys. Rev. Applied 8, 054005 (2017)
H. Sun, Z. Yang, N. V. Kinev, O. S. Kiselev, Y. Lv, Y. Huang, L. Hao, M. Ji, X. Zhou, X. Tu, J. Li, F. Rudau, R. Wieland, J. S. Hampp, O. Kizilaslan, D. Koelle, R. Kleiner, V. P. Koshelets, H.-B. Wang, P. Wu
(Siehe online unter https://doi.org/10.1103/PhysRevApplied.8.054005) - Tuning THz emission properties of Bi2Sr2CaCu2O8+δ intrinsic Josephson junction stacks by charge carrier injection. Supercond. Sci. Technol. – focus issue on Superconductor Terahertz Science and their applications 30, 034006 (2017)
O. Kizilaslan, F. Rudau, R. Wieland, J. S. Hampp, X. J. Zhou, M. Ji, O. Kiselev, N. Kinev, Y. Huang, L. Y. Hao, A. Ishii, M. A. Aksan, T. Hatano, V. P. Koshelets, P. H. Wu, H. B. Wang, D. Koelle, R. Kleiner
(Siehe online unter https://doi.org/10.1088/1361-6668/aa55ae) - Compact high-Tc superconducting terahertz emitter operating up to 86 Kelvin. Phys. Rev. Appl. 10, 024041 (2018)
H. Sun, R. Wieland, Z. Xu, Z. Qi, Y. Lv, Y. Huang, H. Zhang, X. Zhou, J. Li, Y. Wang, F. Rudau, J. S. Hampp, D. Koelle, S. Ishida, H. Eisaki, Y. Yoshida, B. Jin, V. P. Koshelets, R. Kleiner, H.-B. Wang, P. Wu
(Siehe online unter https://doi.org/10.1103/PhysRevApplied.10.024041) - Spectral measurements of THz radiation emitted from intrinsic Josephson junction stacks. 3rd International Conference Terahertz and Microwave Radiation: Generation, Detection and Applications (TERA-2018) EPJ Web of Conferences 195, 05013 (2018)
V. P. Koshelets, N. V. Kinev, A. B. Ermakov, F. Rudau, R. Wieland, D. Koelle, R. Kleiner, and H. B. Wang
(Siehe online unter https://doi.org/10.1051/epjconf/201819505013) - High-quality in-situ fabricated Nb Josephson junctions with black phosphorus barriers. Supercond. Sci. Technol 32, 115005 (2019)
W. Chen, Z. Xu, W. Tian, Y. Lv, M. Yu, X. Zhou, X. Tu, J. Li, S. Li, Y. Wang, H. Yuan, W. Xu, D. Koelle, R. Kleiner, H.-B. Wang, P. H. Wu
(Siehe online unter https://doi.org/10.1088/1361-6668/ab3dc7) - Intrinsic Josephson junctions in high temperature superconductors. Chapter 10 in Fundamentals and Frontiers of the Josephson Effect, F. Tafuri (ed.), Springer Series in Materials Science 286, 367 (2019)
R. Kleiner and H. B. Wang
(Siehe online unter https://doi.org/10.1007/978-3-030-20726-7_10) - Nanoscale photovoltaic responses in 3D radial junction solar cells revealed by high spatial resolution laser excitation photoelectric microscopy. ACS Nano 13, 10359 (2019)
H. Zhang, Y. Lei, Q. Zhu, T. Qing, T. Zhang, W. Tian, M. Lange, M. Jiang, C. Han, J. Li, D. Koelle, R. Kleiner, W. Xu, Y. Wang, L. Yu, H.-B. Wang, P.-H. Wu
(Siehe online unter https://doi.org/10.1021/acsnano.9b04149) - Observation of a two-mode resonant state in a Bi2Sr2CaCu2O8+δ mesa device for terahertz emission. Phys. Rev. B 100, 144503 (2019)
T. M. Benseman, A. E. Koshelev, V. Vlasko-Vlasov, Y. Hao, U. Welp, W.-K. Kwok, B. Gross, M. Lange, D. Koelle, R. Kleiner, H. Minami, M. Tsujimoto, K. Kadowaki
(Siehe online unter https://doi.org/10.1103/PhysRevB.100.144503) - Resonant cavity modes in Bi2Sr2CaCu2O8+x intrinsic Josephson junction stacks. Phys. Rev. Applied 11, 044004 (2019)
H. Zhang, R. Wieland, W. Chen, O. Kizilaslan, S. Ishida, C. Han, W. Tian, Z. Xu, Z. Qi, Y. Lv, X. Zhou, N. Kinev, E. Dorsch, J. M. Ziegele, D. Koelle, H. Eisaki, Y. Yoshida, V. P. Koshelets, R. Kleiner, H.-B. Wang, P. H. Wu
(Siehe online unter https://doi.org/10.1103/PhysRevApplied.11.044004) - Spectral measurements of THz radiation from intrinsic Josephson junction BSCCO stacks; phase locking of the BSCCO oscillators. NRAO Proceedings of the 30th International Symposium on Space THz Technology (ISSTT2019), Gothenburg, Sweden, April 15-17, 2019
V. P. Koshelets, N. V. Kinev, A. B. Ermakov, R. Wieland, E. Dorsch, O. Kizilaslan, D. Koelle, R. Kleiner, H. B. Wang.
- Terahertz emission from Bi2Sr2CaCu2O8+x intrinsic Josephson junction stacks. J. Appl. Phys. 126, 171101 (2019)
R. Kleiner and H.-B. Wang.
(Siehe online unter https://doi.org/10.1063/1.5116660) - Hybrid Nb/Al/Ba0.5K0.5Fe2As2 sandwich Josephson junctions. Supercond. Sci. Technol 33, 025014 (2020)
W.-H. Tian, Y.-Y. Lv, Z.-Y. Xu, H.-L. Zhang, S.-X. Chen, S.-N. Dong, J. Li, Y.-L. Wang, D. Koelle, R. Kleiner, H.-B. Wang, P.-H. Wu
(Siehe online unter https://doi.org/10.1088/1361-6668/ab601f) - On-chip sensing of hotspots in superconducting terahertz emitters. Nano Lett. 20, 4197 (2020)
X. Zhou, X. Han, D. Koelle, R. Kleiner, U. Welp, X. Zhang, D. Jin
(Siehe online unter https://doi.org/10.1021/acs.nanolett.0c00551) - Vertical Nb/TiOx/Nb Josephson junctions controlled by in-plane hot-electron injection. Phys. Rev. Applied 14, 024008 (2020)
Z. Xu, S. Chen, W. Tian, Z. Qi, W. Yue, H. Du, H., Sun, C. Zhang, J. Wu, S. Dong, Y.- L. Wang, W. Xu, B. Jin, J. Chen, G. Sun, D. Koelle, R. Kleiner, H. B. Wang, P. H. Wu
(Siehe online unter https://doi.org/10.1103/PhysRevApplied.14.024008)
