المؤلفون: Gospodaric, Jan, Shuvaev, Alexey, Mikhailov, Nikolai N., Kvon, Ze D., Novik, Elena G., Pimenov, Andrei

المصدر: Phys. Rev. B 104, 115307 (2021)

مصطلحات موضوعية: Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science, Physics - Optics

الوصف: Quantum wells (QWs) based on mercury telluride (HgTe) thin films provide a large scale of unusual physical properties starting from an insulator via a two-dimensional Dirac semimetal to a three-dimensional topological insulator. These properties result from the dramatic change of the QW band structure with the HgTe film thickness. Although being a key property, these energy dispersion relations cannot be reflected in experiments due to the lack of appropriate tools. Here we report an experimental and theoretical study of two HgTe quantum wells with inverted energy spectrum in which two-dimensional semimetallic states are realized. Using magneto-optical spectroscopy at sub-THz frequencies we were able to obtain information about electron and hole cyclotron masses at all relevant Fermi level positions and different charge densities. The outcome is also supported by a Shubnikov-de Haas analysis of capacitance measurements, which allows obtaining information about the degeneracy of the active modes. From these data, it is possible to reconstruct electron and hole dispersion relations. Detailed comparative analysis of the energy dispersion relations with theoretical calculations demonstrates a good agreement, reflecting even several subtle features like band splitting, the second conduction band, and the overlaps between the first conduction and first valence band. Our study demonstrates that the cyclotron resonance experiments can be efficiently used to directly obtain the band structures of semimetallic 2D materials.
Comment: 8 pages, 5 figures

الوصول الحر: http://arxiv.org/abs/2109.07254Test

المؤلفون: Uaman Svetikova, Tatiana A., de Oliveira, Thales V. A. G., Pashkin, Alexej, Ponomaryov, Alexey, Berger, Christian, Fürst, Lena, Bayer, Florian B., Novik, Elena G., Buhmann, Hartmut, Molenkamp, Laurens W., Helm, Manfred, Kiessling, Tobias, Winnerl, Stephan, Kovalev, Sergey, Astakhov, Georgy V.

المساهمون: Deutsche Forschungsgemeinschaft

المصدر: ACS Photonics ; volume 10, issue 10, page 3708-3714 ; ISSN 2330-4022 2330-4022

مصطلحات موضوعية: Electrical and Electronic Engineering, Atomic and Molecular Physics, and Optics, Biotechnology, Electronic, Optical and Magnetic Materials

الإتاحة: https://doi.org/10.1021/acsphotonics.3c00867Test

المؤلفون: Brüne, Christoph, Thienel, Cornelius, Stuiber, Michael, Böttcher, Jan, Buhmann, Hartmut, Novik, Elena G., Liu, Chao-Xing, Hankiewicz, Ewelina M., Molenkamp, Laurens W.

مصطلحات موضوعية: Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science

الوصف: We report magnetotransport studies on a gated strained HgTe device. This material is a threedimensional topological insulator and exclusively shows surface state transport. Remarkably, the Landau level dispersion and the accuracy of the Hall quantization remain unchanged over a wide density range ($3 \times 10^{11} cm^{-2} < n < 1 \times 10^{12} cm^{-2}$). This implies that even at large carrier densities the transport is surface state dominated, where bulk transport would have been expected to coexist already. Moreover, the density dependence of the Dirac-type quantum Hall effect allows to identify the contributions from the individual surfaces. A $k \cdot p$ model can describe the experiments, but only when assuming a steep band bending across the regions where the topological surface states are contained. This steep potential originates from the specific screening properties of Dirac systems and causes the gate voltage to influence the position of the Dirac points rather than that of the Fermi level.
Comment: 12 pages 4 figures

الوصول الحر: http://arxiv.org/abs/1407.6537Test

المؤلفون: Michetti, Paolo, Budich, Jan C., Novik, Elena G., Recher, Patrik

المصدر: Physical Review B 85, 125309 (2012)

مصطلحات موضوعية: Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science

الوصف: The field of topological insulators (TIs) is rapidly growing. Concerning possible applications, the search for materials with an easily controllable TI phase is a key issue. The quantum spin Hall effect, characterized by a single pair of helical edge modes protected by time-reversal symmetry, has been demonstrated in HgTe-based quantum wells (QWs) with an inverted bandgap. We analyze the topological properties of a generically coupled HgTe-based double QW (DQW) and show how in such a system a TI phase can be driven by an inter-layer bias voltage, even when the individual layers are non-inverted. We argue, that this system allows for similar (layer-)pseudospin based physics as in bilayer graphene but with the crucial absence of a valley degeneracy.
Comment: 9 pages, 8 figures, extended version (accepted Phys. Rev. B)

الوصول الحر: http://arxiv.org/abs/1107.4108Test

المؤلفون: Thienel, Cornelius, Stuiber, Michael, Böttcher, Jan, Buhmann, Hartmut, Novik, Elena G., Liu, Chao-Xing, Hankiewicz, Ewelina M., Molenkamp, Laurens W., Brüne, Christoph

الوصول الحر: https://www.europeana.eu/item/2048441/item_UVGPDFAIV4L4ZOJQWRHMLDZCT7RYJVFF?utm_source=api&utm_medium=api&utm_campaign=YuvuWBeCaTest

المؤلفون: Shuvaev, Alexey, Dziom, Vlad, Gospodarič, Jan, Novik, Elena G., Dobretsova, Alena A., Mikhailov, Nikolay N., Kvon, Ze Don, Pimenov, Andrei

المصدر: Nanomaterials (2079-4991); Jul2022, Vol. 12 Issue 14, pN.PAG-N.PAG, 10p

مصطلحات موضوعية: CYCLOTRON resonance, CHARGE carriers, THIN films, ENERGY bands, TOPOLOGICAL insulators

مستخلص: Mercury telluride (HgTe) thin films with a critical thickness of 6.5 nm are predicted to possess a gapless Dirac-like band structure. We report a comprehensive study on gated and optically doped samples by magnetooptical spectroscopy in the THz range. The quasi-classical analysis of the cyclotron resonance allowed the mapping of the band dispersion of Dirac charge carriers in a broad range of electron and hole doping. A smooth transition through the charge neutrality point between Dirac holes and electrons was observed. An additional peak coming from a second type of holes with an almost density-independent mass of around 0.04 m 0 was detected in the hole-doping range and attributed to an asymmetric spin splitting of the Dirac cone. Spectroscopic evidence for disorder-induced band energy fluctuations could not be detected in present cyclotron resonance experiments. [ABSTRACT FROM AUTHOR]

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المؤلفون: Michetti, Paolo, Budich, Jan C., Novik, Elena G., Recher, Patrik

المصدر: Physical Review B ; volume 85, issue 12 ; ISSN 1098-0121 1550-235X

الإتاحة: https://doi.org/10.1103/physrevb.85.125309Test

المؤلفون: Hancock, Jason N., van Mechelen, J. L. M., Kuzmenko, Alexey B., van der Marel, Dirk, Brüne, Christoph, Novik, Elena G., Astakhov, Georgy V., Buhmann, Hartmut, Molenkamp, Laurens W.

المصدر: Physical Review Letters ; volume 107, issue 13 ; ISSN 0031-9007 1079-7114

مصطلحات موضوعية: General Physics and Astronomy

الإتاحة: https://doi.org/10.1103/physrevlett.107.136803Test

المؤلفون: Hancock, Jason N., van Mechelen, J. L. M., Kuzmenko, Alexey B., van der Marel, Dirk, Brüne, Christoph, Novik, Elena G., Astakhov, Georgy V., Buhmann, Hartmut, Molenkamp, Laurens W.

المصدر: Physical Review Letters ; volume 107, issue 14 ; ISSN 0031-9007 1079-7114

مصطلحات موضوعية: General Physics and Astronomy

الإتاحة: https://doi.org/10.1103/physrevlett.107.149903Test

المؤلفون: Liu, Jian, Buhmann, Hartmut, Novik, Elena G., Gui, Yongsheng, Hock, Volkmar, Becker, Charles R., Molenkamp, Laurens W.

المصدر: physica status solidi (b) ; volume 243, issue 4, page 835-838 ; ISSN 0370-1972 1521-3951

الوصف: Low temperature magnetotransport measurements have been used to study the exchange interactions in Hg 1– x Mn x Te magnetic quantum wells (QWs). An analysis of Shubnikov–de Haas oscillations in conjunction with 8 × 8 k · p bandstructure calculations allow the exchange constants N 0 α and N 0 β , the antiferromagnetic temperature T 0 , and the effective spin S 0 to be determined. The latter displays a distinct temperature dependence and appears to be enhanced compared with bulk materials of equivalent Mn concentrations. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

الإتاحة: https://doi.org/10.1002/pssb.200564610Test