Probe-dependent Dirac-point gap in the gadolinium-doped thallium-based topological insulator TlBi0.9Gd0.1Se2

Autor: Filnov, S. O., Klimovskikh, Ilya I., Estyunin, D., Fedorov, Alexander, Voroshnin, Vladimir Yu., Koroleva, A. V., Rybkin, Artem G., Shevchenko, E. V., Aliev, Ziya S., Babanly, M. B., Amiraslanov, I. R., Mamedov, Nazim T., Schwier, E. F., Miyamoto, Koji, Okuda, Taichi, Kumar, S., Kimura, A., Misheneva, V. M., Shikin, Alexander M., Chulkov, Eugene V.
Přispěvatelé: Saint Petersburg State University, Russian Science Foundation, Ministry of Science and Higher Education of the Russian Federation, Science Development Foundation under the President of the Republic of Azerbaijan, Federal Foreign Office (Germany), German Academic Exchange Service, Helmholtz-Zentrum Berlin for Materials and Energy, Hiroshima University, Japan Society for the Promotion of Science
Rok vydání: 2020
Zdroj: Digital.CSIC. Repositorio Institucional del CSIC
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Popis: A tunable gap in the topological surface state is of great interest for novel spintronic devices and applications in quantum computing. Here, we study the surface electronic structure and magnetic properties of the Gd-doped topological insulator TlBi0.9Gd0.1Se2. Utilizing superconducting quantum interference device magnetometry, we show paramagnetic behavior down to 2 K. Combining spin- and angle-resolved photoemission spectroscopy with different polarizations of light, we demonstrate that the topological surface state is characterized by the Dirac cone with a helical spin structure and confirm its localization within the bulk band gap. By using different light sources in photoemission spectroscopy, various Dirac-point gap values were observed: 50 meV for hν=18eV and 20 meV for hν=6.3eV. Here, we discuss the gap observation by the angle-resolved photoemission spectroscopy method as a consequence of the scattering processes. Simulating the corresponding spectral function, we demonstrate that the asymmetric energy-distribution curve of the surface state leads to an overestimation of the corresponding gap value. We speculate that 20 meV in our case is a trustworthy value and attribute this gap to be originated by scattering both on magnetic and charge impurities provided by Gd atoms and surface defects. Given the complexity and importance of scattering processes in the topological surface state together with our observations of distinctive photoemission asymmetry, we believe our results are important for research of the massive Dirac fermions in novel quantum materials.
This work was supported by St. Petersburg State University Project (ID No. 51126254), by the Russian Science Foundation (Grant No. 18-12-00062), by the Ministry of Science and Higher Education of the Russian Federation (Grant No 2020-1902-01-058), and by the Science Development Foundation under the President of the Republic of Azerbaijan (Grant No. EIF-BGM-4-RFTF-1/2017-1/04/1-M-02). The studies were also carried out at the resource centers of St. Petersburg State University “Physical Methods for Surface Investigation” and “Diagnosis of Functional Materials for Medicine, Pharmacology, and Nanoelectronics.” In addition, the work was supported by the German-Russian Interdisciplinary Science Center (G-RISC) funded by the German Federal Foreign Office via the German Academic Exchange Service (DAAD) and Russian-German Laboratory at BESSY II (Helmholtz Zentrum, Berlin). We thank the Hiroshima Synchrotron Radiation Center (Proposal No. 18BG026), Helmholtz-Zentrum Berlin für Materialien und Energie for the allocation of synchrotron radiation beam times, and the N-BARD, Hiroshima University for supplying liquid helium. A.K. was financially supported by KAKENHI (Grants No. 17H06138, No. 17H06152, and No. 18H03683).
Databáze: OpenAIRE
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