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1. Surface states and Rashba-type spin polarization in antiferromagnetic MnBi$_2$Te$_4$

Author

Vidal, R. C., Bentmann, H., Peixoto, T. R. F., Zeugner, A., Moser, S., Min, C. H., Schatz, S., Kissner, K., Ünzelmann, M., Fornari, C. I., Vasili, H. B., Valvidares, M., Sakamoto, K., Mondal, D., Fujii, J., Vobornik, I., Jung, S., Cacho, C., Kim, T. K., Koch, R. J., Jozwiak, C., Bostwick, A., Denlinger, J. D., Rotenberg, E., Buck, J., Hoesch, M., Diekmann, F., Rohlf, S., Kalläne, M., Rossnagel, K., Otrokov, M. M., Chulkov, E. V., Ruck, M., Isaeva, A., and Reinert, F.

Subjects
Condensed Matter - Strongly Correlated Electrons
Abstract

The layered van der Waals antiferromagnet MnBi$_2$Te$_4$ has been predicted to combine the band ordering of archetypical topological insulators such as Bi$_2$Te$_3$ with the magnetism of Mn, making this material a viable candidate for the realization of various magnetic topological states. We have systematically investigated the surface electronic structure of MnBi$_2$Te$_4$(0001) single crystals by use of spin- and angle-resolved photoelectron spectroscopy experiments. In line with theoretical predictions, the results reveal a surface state in the bulk band gap and they provide evidence for the influence of exchange interaction and spin-orbit coupling on the surface electronic structure., Comment: Revised version

Published
2019
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2. Systematics of electronic and magnetic properties in the transition metal doped Sb$_2$Te$_3$ quantum anomalous Hall platform

Author

Islam, M F., Canali, C. M., Pertsova, A., Balatsky, A., Mahatha, S. K., Carbone, C., Barla, A., Kokh, K. A., Tereshchenk, O. E., Jiménez, E., Brookes, N. B., Gargiani, P., Valvidares, M., Schatz, S., Peixoto, T. R. F., Bentmann, H., Reinert, F., Jung, J., Bathon, T., Fauth, K., Bode, M., and Sessi, P.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

The quantum anomalous Hall effect (QAHE) has recently been reported to emerge in magnetically-doped topological insulators. Although its general phenomenology is well established, the microscopic origin is far from being properly understood and controlled. Here we report on a detailed and systematic investigation of transition-metal (TM)-doped Sb$_2$Te$_3$. By combining density functional theory (DFT) calculations with complementary experimental techniques, i.e., scanning tunneling microscopy (STM), resonant photoemission (resPES), and x-ray magnetic circular dichroism (XMCD), we provide a complete spectroscopic characterization of both electronic and magnetic properties. Our results reveal that the TM dopants not only affect the magnetic state of the host material, but also significantly alter the electronic structure by generating impurity-derived energy bands. Our findings demonstrate the existence of a delicate interplay between electronic and magnetic properties in TM-doped TIs. In particular, we find that the fate of the topological surface states critically depends on the specific character of the TM impurity: while V- and Fe-doped Sb$_2$Te$_3$ display resonant impurity states in the vicinity of the Dirac point, Cr and Mn impurities leave the energy gap unaffected. The single-ion magnetic anisotropy energy and easy axis, which control the magnetic gap opening and its stability, are also found to be strongly TM impurity-dependent and can vary from in-plane to out-of-plane depending on the impurity and its distance from the surface. Overall, our results provide general guidelines for the realization of a robust QAHE in TM-doped Sb$_2$Te$_3$ in the ferromagnetic state., Comment: 40 pages, 13 figures

Published
2018
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3. Surface states and Rashba-type spin polarization in antiferromagnetic MnBi2Te4 (0001)

Author

Vidal, RC, Bentmann, H, Peixoto, TRF, Zeugner, A, Moser, S, Min, CH, Schatz, S, Kißner, K, Ünzelmann, M, Fornari, CI, Vasili, HB, Valvidares, M, Sakamoto, K, Mondal, D, Fujii, J, Vobornik, I, Jung, S, Cacho, C, Kim, TK, Koch, RJ, Jozwiak, C, Bostwick, A, Denlinger, JD, Rotenberg, E, Buck, J, Hoesch, M, Diekmann, F, Rohlf, S, Kalläne, M, Rossnagel, K, Otrokov, MM, Chulkov, EV, Ruck, M, Isaeva, A, and Reinert, F

Abstract

The layered van der Waals antiferromagnet MnBi2Te4 has been predicted to combine the band ordering of archetypical topological insulators such as Bi2Te3 with the magnetism of Mn, making this material a viable candidate for the realization of various magnetic topological states. We have systematically investigated the surface electronic structure of MnBi2Te4(0001) single crystals by use of spin- and angle-resolved photoelectron spectroscopy experiments. In line with theoretical predictions, the results reveal a surface state in the bulk band gap and they provide evidence for the influence of exchange interaction and spin-orbit coupling on the surface electronic structure.

Published
2019

5. Prediction and observation of an antiferromagnetic topological insulator

Author

Otrokov, M.M., Klimovskikh, I.I., Bentmann, H., Estyunin, D., Zeugner, A., Aliev, Z.S., Gass, S., Wolter, A.U.B., Koroleva, A.V., Shikin, A.M., Blanco-Rey, M., Hoffmann, M., Rusinov, I.P., Vyazovskaya, A.Yu., Eremeev, S.V., Koroteev, Yu.M., Kuznetsov, V.M., Freyse, F., Sanchez-Barriga, J., Amiraslanov, I.R., Babanly, M.B., Mamedov, N.T., Abdullayev, N.A., Zverev, V.N., Alfonsov, A., Kataev, V., Buchner, B., Schwier, E.F., Kumar, S., Kimura, A., Petaccia, L., Di Santo, G., Vidal, R.C., Schatz, S., Kissner, K., Unzelmann, M., Min, C.H., Moser, Simon, Peixoto, T.R.F., Reinert, F., Ernst, A., Echenique, P.M., Isaeva, A., and Chulkov, E.V.

Subjects
Ferromagnetism -- Observations, Semiconductors -- Testing, Magnesium compounds -- Atomic properties -- Magnetic properties, Quantum theory -- Methods, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Magnetic topological insulators are narrow-gap semiconductor materials that combine non-trivial band topology and magnetic order.sup.1. Unlike their nonmagnetic counterparts, magnetic topological insulators may have some of the surfaces gapped, which enables a number of exotic phenomena that have potential applications in spintronics.sup.1, such as the quantum anomalous Hall effect.sup.2 and chiral Majorana fermions.sup.3. So far, magnetic topological insulators have only been created by means of doping nonmagnetic topological insulators with 3d transition-metal elements; however, such an approach leads to strongly inhomogeneous magnetic.sup.4 and electronic.sup.5 properties of these materials, restricting the observation of important effects to very low temperatures.sup.2,3. An intrinsic magnetic topological insulator--a stoichiometric well ordered magnetic compound--could be an ideal solution to these problems, but no such material has been observed so far. Here we predict by ab initio calculations and further confirm using various experimental techniques the realization of an antiferromagnetic topological insulator in the layered van der Waals compound MnBi.sub.2Te.sub.4. The antiferromagnetic ordering that MnBi.sub.2Te.sub.4 shows makes it invariant with respect to the combination of the time-reversal and primitive-lattice translation symmetries, giving rise to a Z.sub.2 topological classification; Z.sub.2 = 1 for MnBi.sub.2Te.sub.4, confirming its topologically nontrivial nature. Our experiments indicate that the symmetry-breaking (0001) surface of MnBi.sub.2Te.sub.4 exhibits a large bandgap in the topological surface state. We expect this property to eventually enable the observation of a number of fundamental phenomena, among them quantized magnetoelectric coupling.sup.6-8 and axion electrodynamics.sup.9,10. Other exotic phenomena could become accessible at much higher temperatures than those reached so far, such as the quantum anomalous Hall effect.sup.2 and chiral Majorana fermions.sup.3. An intrinsic antiferromagnetic topological insulator, MnBi.sub.2Te.sub.4, is theoretically predicted and then realized experimentally, with implications for the study of exotic quantum phenomena., Author(s): M. M. Otrokov [sup.1] [sup.2] [sup.3] [sup.4] , I. I. Klimovskikh [sup.4] , H. Bentmann [sup.5] , D. Estyunin [sup.4] , A. Zeugner [sup.6] , Z. S. Aliev [sup.7] [...]

Published
2019
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7. 071 The adaptive response of old ABCB5+ MSCs is impaired upon exposure to LPS

Author

Haas, P., primary, Shekhawat, K., additional, Maity, P., additional, Schatz, S., additional, Munir, S., additional, Wang, Y., additional, Basu, A., additional, Crisan, D., additional, Bauer, R., additional, Mauerer, S., additional, Spellerberg, B., additional, Ganss, C., additional, Wlaschek, M., additional, Kluth, M., additional, and Scharffetter-Kochanek, K., additional

Published
2023
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8. Development of the NOGGO GIS v1 Assay, a Comprehensive Hybrid-Capture-Based NGS Assay for Therapeutic Stratification of Homologous Repair Deficiency Driven Tumors and Clinical Validation

Author

Willing, E, Vollbrecht, C, Vössing, C, Weist, P, Schallenberg, S, Herbst, J, Schatz, S, Jóri, B, Bataillon, G, Harter, P, Salutari, V, Martin, A, Vergote, I, Colombo, N, Roeper, J, Berg, T, Berger, R, Kah, B, Noettrup, T, Falk, M, Arndt, K, Polten, A, Ray-Coquard, I, Selzam, F, Pirngruber, J, Schmidt, S, Hummel, M, Tiemann, M, Horst, D, Sehouli, J, Pujade-Lauraine, E, Tiemann, K, Braicu, E, Heukamp, L, Willing, Eva-Maria, Vollbrecht, Claudia, Vössing, Christine, Weist, Peggy, Schallenberg, Simon, Herbst, Johanna M, Schatz, Stefanie, Jóri, Balázs, Bataillon, Guillaume, Harter, Philipp, Salutari, Vanda, Martin, Antonio Gonzáles, Vergote, Ignace, Colombo, Nicoletta, Roeper, Julia, Berg, Tobias, Berger, Regina, Kah, Bettina, Noettrup, Trine Jakobi, Falk, Markus, Arndt, Kathrin, Polten, Andreas, Ray-Coquard, Isabelle, Selzam, Franziska, Pirngruber, Judith, Schmidt, Stefanie, Hummel, Michael, Tiemann, Markus, Horst, David, Sehouli, Jalid, Pujade-Lauraine, Eric, Tiemann, Katharina, Braicu, Elena Ioana, Heukamp, Lukas C, Willing, E, Vollbrecht, C, Vössing, C, Weist, P, Schallenberg, S, Herbst, J, Schatz, S, Jóri, B, Bataillon, G, Harter, P, Salutari, V, Martin, A, Vergote, I, Colombo, N, Roeper, J, Berg, T, Berger, R, Kah, B, Noettrup, T, Falk, M, Arndt, K, Polten, A, Ray-Coquard, I, Selzam, F, Pirngruber, J, Schmidt, S, Hummel, M, Tiemann, M, Horst, D, Sehouli, J, Pujade-Lauraine, E, Tiemann, K, Braicu, E, Heukamp, L, Willing, Eva-Maria, Vollbrecht, Claudia, Vössing, Christine, Weist, Peggy, Schallenberg, Simon, Herbst, Johanna M, Schatz, Stefanie, Jóri, Balázs, Bataillon, Guillaume, Harter, Philipp, Salutari, Vanda, Martin, Antonio Gonzáles, Vergote, Ignace, Colombo, Nicoletta, Roeper, Julia, Berg, Tobias, Berger, Regina, Kah, Bettina, Noettrup, Trine Jakobi, Falk, Markus, Arndt, Kathrin, Polten, Andreas, Ray-Coquard, Isabelle, Selzam, Franziska, Pirngruber, Judith, Schmidt, Stefanie, Hummel, Michael, Tiemann, Markus, Horst, David, Sehouli, Jalid, Pujade-Lauraine, Eric, Tiemann, Katharina, Braicu, Elena Ioana, and Heukamp, Lukas C

Abstract

The worldwide approval of the combination maintenance therapy of olaparib and bevacizumab in advanced high-grade serous ovarian cancer requires complex molecular diagnostic assays that are sufficiently robust for the routine detection of driver mutations in homologous recombination repair (HRR) genes and genomic instability (GI), employing formalin-fixed (FFPE) paraffin-embedded tumor samples without matched normal tissue. We therefore established a DNA-based hybrid capture NGS assay and an associated bioinformatic pipeline that fulfils our institution’s specific needs. The assay ́s target regions cover the full exonic territory of relevant cancer-related genes and HRR genes and more than 20,000 evenly distributed single nucleotide polymorphism (SNP) loci to allow for the detection of genome-wide allele specific copy number alterations (CNA). To determine GI status, we implemented an %CNA score that is robust across a broad range of tumor cell content (25–85%) often found in routine FFPE samples. The assay was established using high-grade serous ovarian cancer samples for which BRCA1 and BRCA2 mutation status as well as Myriad MyChoice homologous repair deficiency (HRD) status was known. The NOGGO (Northeastern German Society for Gynecologic Oncology) GIS (GI-Score) v1 assay was clinically validated on more than 400 samples of the ENGOT PAOLA-1 clinical trial as part of the European Network for Gynaecological Oncological Trial groups (ENGOT) HRD European Initiative. The “NOGGO GIS v1 assay” performed using highly robust hazard ratios for progression-free survival (PFS) and overall survival (OS), as well a significantly lower dropout rate than the Myriad MyChoice clinical trial assay supporting the clinical utility of the assay. We also provide proof of a modular and scalable routine diagnostic method, that can be flexibly adapted and adjusted to meet future clinical needs, emerging biomarkers, and further tumor entities.

Published
2023

10. Fetale Anämie bei pränatalem Volvulus

Author

Shen, S, additional, Delius, M, additional, Schneider, M, additional, Schatz, S, additional, Münsterer, O, additional, Mühling, J, additional, Pinto Ribeiro, P, additional, Mahner, S, additional, and Büchel, J, additional

Published
2022
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18. A multi‐institutional randomized controlled trial comparing first‐generation transrectal high‐resolution micro‐ultrasound with conventional frequency transrectal ultrasound for prostate biopsy

Author

Pavlovich, C. P., primary, Hyndman, M. E., additional, Eure, G., additional, Ghai, S., additional, Caumartin, Y., additional, Herget, E., additional, Young, J. D., additional, Wiseman, D., additional, Caughlin, C., additional, Gray, R., additional, Wason, S., additional, Mettee, L., additional, Lodde, M., additional, Toi, A., additional, Dujardin, T., additional, Lance, R., additional, Schatz, S. M., additional, Fabrizio, M., additional, Malcolm, J. B., additional, and Fradet, V., additional

Published
2020
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20. Comparing magnetic ground-state properties of the V- and Cr-doped topological insulator (Bi,Sb)2Te3

Author

Tcakaev, A., primary, Zabolotnyy, V. B., additional, Green, R. J., additional, Peixoto, T. R. F., additional, Stier, F., additional, Dettbarn, M., additional, Schreyeck, S., additional, Winnerlein, M., additional, Vidal, R. Crespo, additional, Schatz, S., additional, Vasili, H. B., additional, Valvidares, M., additional, Brunner, K., additional, Gould, C., additional, Bentmann, H., additional, Reinert, F., additional, Molenkamp, L. W., additional, and Hinkov, V., additional

Published
2020
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21. Surface states and Rashba-type spin polarization in antiferromagnetic MnBi2Te4 (0001)

Author

Vidal, R. C., Bentmann, Hendrik, Peixoto, T. R. F., Zeugner, Alexander, Moser, S., Min, C. H., Schatz, S., Kißner, K., Ünzelmann, M., Fornari, C. I., Vasili, Hari Babu, Valvidares, Manuel, Sakamoto, K., Fujii, Jun, Vobornik, Ivana, Jung, S., Cacho, Cephise, Kim, T. K., Koch, Roland J., Jozwiak, C, Bostwick, A., Denlinger, J. D., Rotenberg, E., Buck, J., Hoesch, Moritz, Diekmann, F., Rohlf, S., Kalläne, M., Rossnagel, K., Otrokov, M. M., Chulkov, Eugene V., Ruck, M., Isaeva, Anna, Reinert, Friedrich, Ministerio de Economía y Competitividad (España), Tomsk State University, Saint Petersburg State University, Russian Foundation for Basic Research, Swiss National Science Foundation, and Diputación Foral de Guipúzcoa

Abstract

The layered van der Waals antiferromagnet MnBi2Te4 has been predicted to combine the band ordering of archetypical topological insulators such as Bi2Te3 with the magnetism of Mn, making this material a viable candidate for the realization of various magnetic topological states. We have systematically investigated the surface electronic structure of MnBi2Te4(0001) single crystals by use of spin- and angle-resolved photoelectron spectroscopy experiments. In line with theoretical predictions, the results reveal a surface state in the bulk band gap and they provide evidence for the influence of exchange interaction and spin-orbit coupling on the surface electronic structure., We acknowledge financial support from the DFG through SFB1170 ’Tocotronics’, SFB1143 ’Correlated Magnetism’, SPP 1666 ’Topological insulators’, ERA-Chemistry Programm (RU-776/15-1), and the Wurzburg-Dresden Cluster of ¨Excellence on Complexity and Topology in Quantum Matter – ct.qmat (EXC 2147, project-id 39085490). We also acknowledge the support by Spanish Ministerio de Economia y Competitividad (MINECO Grant No. FIS2016-75862-P), Academic D.I. Mendeleev Fund Program of Tomsk State University (Project No. 8.1.01.2018), the Saint Petersburg State University grant for scientic investigations (Grant No. 15.61.202.2015), and Russian Foundation for Basic Research (Grant No. 18-52-06009). S.M. acknowledges support by the Swiss National Science Foundation (Grant No. P300P2-171221). This research used resources of the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. We acknowledge Diamond Light Source for access to beamline I05 (proposals No. SI19278 and No. SI22468) that contributed to the results presented here. Parts of this research were carried out at PETRA III (DESY, Hamburg, Germany) under Proposal No. I-20180510. This work has been partly performed in the framework of the Nanoscience Foundry and Fine Analysis (NFFA-MIUR, Italy) facility. M.M.O. acknowledges support by the Diputacion Foral de Gipuzkoa ((SAREA 2018 - RED ´2018, project no. 2018-CIEN-000025-01).

Published
2019

22. Surface states and Rashba-type spin polarization in antiferromagnetic $MnBi_{2}Te_{4}$ (0001)

Author

Vidal, R. C., Bentmann, H., Peixoto, T. R. F., Zeugner, A., Moser, S., Min, C.-H., Schatz, S., Kißner, K., Ünzelmann, M., Fornari, C. I., Vasili, H. B., Valvidares, M., Sakamoto, K., Mondal, D., Fujii, J., Vobornik, I., Jung, S., Cacho, C., Kim, T. K., Koch, R. J., Jozwiak, C., Bostwick, A., Denlinger, J. D., Rotenberg, E., Buck, J., Hoesch, M., Diekmann, F., Rohlf, S., Kalläne, M., Rossnagel, K., Otrokov, M. M., Chulkov, E. V., Ruck, M., Isaeva, A., and Reinert, F.

Subjects
Engineering, Fluids & Plasmas, Physical Sciences, Chemical Sciences, ddc:530
Abstract

Physical review / B covering condensed matter and materials physics 100(12), 121104-1-121104-6 (2019). doi:10.1103/PhysRevB.100.121104, The layered van der Waals antiferromagnet $MnBi_{2}Te_{4}$ (0001) has been predicted to combine the band ordering of archetypical topological insulators such as Bi2Te3 with the magnetism of Mn, making this material a viable candidate for the realization of various magnetic topological states. We have systematically investigated the surface electronic structure of $MnBi_{2}Te_{4}$ (0001)single crystals by use of spin- and angle-resolved photoelectron spectroscopy experiments. In line with theoretical predictions, the results reveal a surface state in the bulk band gap and they provide evidence for the influence of exchange interaction and spin-orbit coupling on the surface electronic structure., Published by Inst., Woodbury, NY

Published
2019

23. Surface states and Rashba-type spin polarization in antiferromagnetic MnBi2Te4 (0001)

Author

Ministerio de Economía y Competitividad (España), Tomsk State University, Saint Petersburg State University, Russian Foundation for Basic Research, Swiss National Science Foundation, Diputación Foral de Guipúzcoa, Vidal, R. C., Bentmann, Hendrik, Peixoto, T. R. F., Zeugner, Alexander, Moser, S., Min, C. H., Schatz, S., Kißner, K., Ünzelmann, M., Fornari, C. I., Vasili, Hari Babu, Valvidares, Manuel, Sakamoto, K., Fujii, Jun, Vobornik, Ivana, Jung, S., Cacho, Cephise, Kim, T. K., Koch, Roland J., Jozwiak, C, Bostwick, A., Denlinger, J. D., Rotenberg, E., Buck, J., Hoesch, Moritz, Diekmann, F., Rohlf, S., Kalläne, M., Rossnagel, K., Otrokov, M. M., Chulkov, Eugene V., Ruck, M., Isaeva, Anna, Reinert, Friedrich, Ministerio de Economía y Competitividad (España), Tomsk State University, Saint Petersburg State University, Russian Foundation for Basic Research, Swiss National Science Foundation, Diputación Foral de Guipúzcoa, Vidal, R. C., Bentmann, Hendrik, Peixoto, T. R. F., Zeugner, Alexander, Moser, S., Min, C. H., Schatz, S., Kißner, K., Ünzelmann, M., Fornari, C. I., Vasili, Hari Babu, Valvidares, Manuel, Sakamoto, K., Fujii, Jun, Vobornik, Ivana, Jung, S., Cacho, Cephise, Kim, T. K., Koch, Roland J., Jozwiak, C, Bostwick, A., Denlinger, J. D., Rotenberg, E., Buck, J., Hoesch, Moritz, Diekmann, F., Rohlf, S., Kalläne, M., Rossnagel, K., Otrokov, M. M., Chulkov, Eugene V., Ruck, M., Isaeva, Anna, and Reinert, Friedrich

Abstract

The layered van der Waals antiferromagnet MnBi2Te4 has been predicted to combine the band ordering of archetypical topological insulators such as Bi2Te3 with the magnetism of Mn, making this material a viable candidate for the realization of various magnetic topological states. We have systematically investigated the surface electronic structure of MnBi2Te4(0001) single crystals by use of spin- and angle-resolved photoelectron spectroscopy experiments. In line with theoretical predictions, the results reveal a surface state in the bulk band gap and they provide evidence for the influence of exchange interaction and spin-orbit coupling on the surface electronic structure.

Published
2019

24. Prediction and observation of an antiferromagnetic topological insulator

Author

Ministerio de Economía y Competitividad (España), Eusko Jaurlaritza, Tomsk State University, Saint Petersburg State University, Russian Science Foundation, Russian Foundation for Basic Research, Science Development Foundation under the President of the Republic of Azerbaijan, Diputación Foral de Guipúzcoa, German Research Foundation, Russian Academy of Sciences, Otrokov, M. M., Klimovskikh, Ilya I., Bentmann, Hendrik, Estyunin, D., Zeugner, Alexander, Aliev, Ziya S., Gaß, S., Wolter, A. U. B., Koroleva, A. V., Shikin, Alexander M., Blanco-Rey, María, Hoffmann, Martin, Rusinov, Igor P., Vyazovskaya, Alexandra Yu., Eremeev, Sergey V., Koroteev, Yuri M., Kuznetsov, V. M., Freyse, Friedrich, Sánchez-Barriga, Jaime, Amiraslanov, I. R., Babanly, M. B., Mamedov, Nazim T., Abdullayev, Nadir A., Zverev, Vladimir N., Alfonsov, A., Kataev, V., Büchner, Bernd, Schwier, E. F., Kumar, Sumit, Kimura, A., Petaccia, Luca, Di Santo, Giovanni, Vidal, R. C., Schatz, S., Kißner, K., Ünzelmann, M., Min, C. H., Moser, S., Peixoto, T. R. F., Reinert, Friedrich, Ernst, Arthur, Chulkov, Eugene V., Ministerio de Economía y Competitividad (España), Eusko Jaurlaritza, Tomsk State University, Saint Petersburg State University, Russian Science Foundation, Russian Foundation for Basic Research, Science Development Foundation under the President of the Republic of Azerbaijan, Diputación Foral de Guipúzcoa, German Research Foundation, Russian Academy of Sciences, Otrokov, M. M., Klimovskikh, Ilya I., Bentmann, Hendrik, Estyunin, D., Zeugner, Alexander, Aliev, Ziya S., Gaß, S., Wolter, A. U. B., Koroleva, A. V., Shikin, Alexander M., Blanco-Rey, María, Hoffmann, Martin, Rusinov, Igor P., Vyazovskaya, Alexandra Yu., Eremeev, Sergey V., Koroteev, Yuri M., Kuznetsov, V. M., Freyse, Friedrich, Sánchez-Barriga, Jaime, Amiraslanov, I. R., Babanly, M. B., Mamedov, Nazim T., Abdullayev, Nadir A., Zverev, Vladimir N., Alfonsov, A., Kataev, V., Büchner, Bernd, Schwier, E. F., Kumar, Sumit, Kimura, A., Petaccia, Luca, Di Santo, Giovanni, Vidal, R. C., Schatz, S., Kißner, K., Ünzelmann, M., Min, C. H., Moser, S., Peixoto, T. R. F., Reinert, Friedrich, Ernst, Arthur, and Chulkov, Eugene V.

Abstract

Magnetic topological insulators are narrow-gap semiconductor materials that combine non-trivial band topology and magnetic order. Unlike their nonmagnetic counterparts, magnetic topological insulators may have some of the surfaces gapped, which enables a number of exotic phenomena that have potential applications in spintronics, such as the quantum anomalous Hall effect and chiral Majorana fermions. So far, magnetic topological insulators have only been created by means of doping nonmagnetic topological insulators with 3d transition-metal elements; however, such an approach leads to strongly inhomogeneous magnetic and electronic properties of these materials, restricting the observation of important effects to very low temperatures. An intrinsic magnetic topological insulator—a stoichiometric well ordered magnetic compound—could be an ideal solution to these problems, but no such material has been observed so far. Here we predict by ab initio calculations and further confirm using various experimental techniques the realization of an antiferromagnetic topological insulator in the layered van der Waals compound MnBiTe. The antiferromagnetic ordering that MnBiTe shows makes it invariant with respect to the combination of the time-reversal and primitive-lattice translation symmetries, giving rise to a ℤ topological classification; ℤ = 1 for MnBiTe, confirming its topologically nontrivial nature. Our experiments indicate that the symmetry-breaking (0001) surface of MnBiTe exhibits a large bandgap in the topological surface state. We expect this property to eventually enable the observation of a number of fundamental phenomena, among them quantized magnetoelectric coupling and axion electrodynamics. Other exotic phenomena could become accessible at much higher temperatures than those reached so far, such as the quantum anomalous Hall effect and chiral Majorana fermions.

Published
2019

31. A multi‐institutional randomized controlled trial comparing first‐generation transrectal high‐resolution micro‐ultrasound with conventional frequency transrectal ultrasound for prostate biopsy.

Author

Pavlovich, C. P., Hyndman, M. E., Eure, G., Ghai, S., Caumartin, Y., Herget, E., Young, J. D., Wiseman, D., Caughlin, C., Gray, R., Wason, S., Mettee, L., Lodde, M., Toi, A., Dujardin, T., Lance, R., Schatz, S. M., Fabrizio, M., Malcolm, J. B., and Fradet, V.

Published
2021
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32. Electronic structure and morphology of epitaxial Bi2Te2Se topological insulator films.

Author

Maaé, H., Schreyeck, S., Schatz, S., Fiedler, S., Seibel, C., Lutz, P., Karczewski, G., Bentmann, H., Gould, C., Brunner, K., Molenkamp, L. W., and Reinert, F.

Subjects
BISMUTH telluride films, SELENIUM films, TOPOLOGICAL insulators, SURFACE preparation, PHOTOELECTRON spectroscopy, SCANNING tunneling microscopy, X-ray photoelectron spectroscopy
Abstract

Epitaxial films of the ternary topological insulator Bi2Te2Se were grown on Si(111) substrates and investigated for their surface electronic properties and morphology. We employ a Se-capping procedure allowing for the preparation of clean films in the surface-analysis experimental setups. Using angle-resolved photoelectron spectroscopy, we determine the dispersion of the topological surface state. With time after surface preparation, the spectroscopic features in the surface electronic structure exhibit significant temperature-dependent shifts to higher binding energies. Scanning tunneling microscopy images show terraces with typical step edge separations of 50 nm-150 nm. X-ray photoelectron spectroscopy indicates an increased Se concentration at the surface. [ABSTRACT FROM AUTHOR]

Published
2014
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33. Systematics of electronic and magnetic properties in the transition metal doped Sb2Te3 quantum anomalous Hall platform

Author

Islam, M. F., Canali, C. M., Pertsova, Anna, Balatsky, Alexander, Mahatha, S. K., Carbone, C., Barla, A., Kokh, K. A., Tereshchenko, O. E., Jimenez, E., Brookes, N. B., Gargiani, P., Valvidares, M., Schatz, S., Peixoto, T. R. F., Bentmann, H., Reinert, F., Jung, J., Bathon, T., Fauth, K., Bode, M., Sessi, P., Islam, M. F., Canali, C. M., Pertsova, Anna, Balatsky, Alexander, Mahatha, S. K., Carbone, C., Barla, A., Kokh, K. A., Tereshchenko, O. E., Jimenez, E., Brookes, N. B., Gargiani, P., Valvidares, M., Schatz, S., Peixoto, T. R. F., Bentmann, H., Reinert, F., Jung, J., Bathon, T., Fauth, K., Bode, M., and Sessi, P.

Abstract

The quantum anomalous Hall effect (QAHE) has recently been reported to emerge in magnetically doped topological insulators. Although its general phenomenology is well established, the microscopic origin is far from being properly understood and controlled. Here, we report on a detailed and systematic investigation of transition metal (TM) doped Sb2Te3. By combining density functional theory calculations with complementary experimental techniques, i.e., scanning tunneling microscopy, resonant photoemission, and x-raymagnetic circular dichroism, we provide a complete spectroscopic characterization of both electronic and magnetic properties. Our results reveal that the TM dopants not only affect the magnetic state of the host material, but also significantly alter the electronic structure by generating impurity-derived energy bands. Our findings demonstrate the existence of a delicate interplay between electronic and magnetic properties in TM doped topological insulators. In particular, we find that the fate of the topological surface states critically depends on the specific character of the TM impurity: while V-and Fe-doped Sb2Te3 display resonant impurity states in the vicinity of the Dirac point, Cr and Mn impurities leave the energy gap unaffected. The single-ion magnetic anisotropy energy and easy axis, which control the magnetic gap opening and its stability, are also found to be strongly TM impurity dependent and can vary from in plane to out of plane depending on the impurity and its distance from the surface. Overall, our results provide general guidelines for the realization of a robust QAHE in TM doped Sb2Te3 in the ferromagnetic state.

Published
2018
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37. Systematics of electronic and magnetic properties in the transition metal doped Sb2Te3 quantum anomalous Hall platform

Author

Islam, M. F., primary, Canali, C. M., additional, Pertsova, A., additional, Balatsky, A., additional, Mahatha, S. K., additional, Carbone, C., additional, Barla, A., additional, Kokh, K. A., additional, Tereshchenko, O. E., additional, Jiménez, E., additional, Brookes, N. B., additional, Gargiani, P., additional, Valvidares, M., additional, Schatz, S., additional, Peixoto, T. R. F., additional, Bentmann, H., additional, Reinert, F., additional, Jung, J., additional, Bathon, T., additional, Fauth, K., additional, Bode, M., additional, and Sessi, P., additional

Published
2018
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39. Academic domains as political battlegrounds: a global enquiry by 99 academics in the fields of education and technology

Author

Al Lily, A.E., Foland, J., Stoloff, D., Gogus, A., Erguvan, I.D., Awshar, M.T., Tondeur, J., Hammond, M., Venter, I.M., Jerry, P., Vlachopoulos, D., Oni, A., Liu, Y., Badosek, R., de la Madrid, M.C.L., Mazzoni, E., Lee, H., Kinley, K., Kalz, M., Sambuu, U., Bushnaq, T., Pinkwart, N., Adedokun-Shittu, N.A., Zander, P.-O.M., Oliver, K., Pombo, L.M.T., Sali, J.B., Gregory, S., Tobgay, S., Joy, M., Elen, J., Jwaifell, M.O.H., Said, M.N.H.M., Al-Saggaf, Y., Naaji, A., White, J., Jordan, K., Gerstein, J., Yapici, İ.U., Sanga, C., Nleya, P.T., Sbihi, B., Lucas, M.R., Mbarika, V., Reiners, T., Schön, S., Sujo-Montes, L., Santally, M., Häkkinen, P., Saif, A.A., Gegenfurtner, A., Schatz, S., Vigil, V.P., Tannahill, C., Partida, S.P., Zhang, Z., Charalambous, K., Moreira, A., Coto, M., Laxman, K., Farley, H.S., Gumbo, M.T., Simsek, A., Ramganesh, E., Birzina, R., Player-Koro, C., Dumbraveanu, R., Ziphorah, M., Mohamudally, N., Thomas, S., Romero, M., Nirmala, M., Cifuentes, L., Osaily, R.Z.K., Omoogun, A.C., Seferoglu, S.S., Elçi, A., Edyburn, D., Moudgalya, K., Ebner, M., Bottino, R., Khoo, E., Pedro, L., Buarki, H., Román-Odio, C., Qureshi, I.A., Khan, M.A., Thornthwaite, C., Kerimkulova, S., Downes, T., Malmi, L., Bardakci, S., Itmazi, J., Rogers, J., Rughooputh, S.D.D.V., Akour, M.A., Henderson, J.B., de Freitas, S., Schrader, P.G., Al Lily, A.E., Foland, J., Stoloff, D., Gogus, A., Erguvan, I.D., Awshar, M.T., Tondeur, J., Hammond, M., Venter, I.M., Jerry, P., Vlachopoulos, D., Oni, A., Liu, Y., Badosek, R., de la Madrid, M.C.L., Mazzoni, E., Lee, H., Kinley, K., Kalz, M., Sambuu, U., Bushnaq, T., Pinkwart, N., Adedokun-Shittu, N.A., Zander, P.-O.M., Oliver, K., Pombo, L.M.T., Sali, J.B., Gregory, S., Tobgay, S., Joy, M., Elen, J., Jwaifell, M.O.H., Said, M.N.H.M., Al-Saggaf, Y., Naaji, A., White, J., Jordan, K., Gerstein, J., Yapici, İ.U., Sanga, C., Nleya, P.T., Sbihi, B., Lucas, M.R., Mbarika, V., Reiners, T., Schön, S., Sujo-Montes, L., Santally, M., Häkkinen, P., Saif, A.A., Gegenfurtner, A., Schatz, S., Vigil, V.P., Tannahill, C., Partida, S.P., Zhang, Z., Charalambous, K., Moreira, A., Coto, M., Laxman, K., Farley, H.S., Gumbo, M.T., Simsek, A., Ramganesh, E., Birzina, R., Player-Koro, C., Dumbraveanu, R., Ziphorah, M., Mohamudally, N., Thomas, S., Romero, M., Nirmala, M., Cifuentes, L., Osaily, R.Z.K., Omoogun, A.C., Seferoglu, S.S., Elçi, A., Edyburn, D., Moudgalya, K., Ebner, M., Bottino, R., Khoo, E., Pedro, L., Buarki, H., Román-Odio, C., Qureshi, I.A., Khan, M.A., Thornthwaite, C., Kerimkulova, S., Downes, T., Malmi, L., Bardakci, S., Itmazi, J., Rogers, J., Rughooputh, S.D.D.V., Akour, M.A., Henderson, J.B., de Freitas, S., and Schrader, P.G.

Abstract

This article theorizes the functional relationship between the human components (i.e., scholars) and non-human components (i.e., structural configurations) of academic domains. It is organized around the following question: in what ways have scholars formed and been formed by the structural configurations of their academic domain? The article uses as a case study the academic domain of education and technology to examine this question. Its authorship approach is innovative, with a worldwide collection of academics (99 authors) collaborating to address the proposed question based on their reflections on daily social and academic practices. This collaboration followed a three-round process of contributions via email. Analysis of these scholars’ reflective accounts was carried out, and a theoretical proposition was established from this analysis. The proposition is of a mutual (yet not necessarily balanced) power (and therefore political) relationship between the human and non-human constituents of an academic realm, with the two shaping one another. One implication of this proposition is that these non-human elements exist as political ‘actors’, just like their human counterparts, having ‘agency’ – which they exercise over humans. This turns academic domains into political (functional or dysfunctional) ‘battlefields’ wherein both humans and non-humans engage in political activities and actions that form the identity of the academic domain. For more information about the authorship approach, please see Al Lily AEA (2015) A crowd-authoring project on the scholarship of educational technology. Information Development.

Published
2017

40. Academic domains as political battlegrounds: A global enquiry by 99 academics in the fields of education and technology

Author

Al Lily, A., Foland, J., Stoloff, D., Gogus, A., Deniz Erguvan, I., Tomé Awshar, M., Tondeur, J., Hammond, M., Venter, I., Jerry, P., Vlachopoulos, D., Oni, A., Liu, Y., Badosek, R., López de la Madrid, M., Mazzoni, E., Lee, H., Kinley, K., Kalz, M., Sambuu, U., Bushnaq, T., Pinkwart, N., Adedokun-Shittu, N., Zander, P., Oliver, K., Pombo, L., Balaban Sali, J., Gregory, S., Tobgay, S., Joy, M., Elen, J., Jwaifell, M., Said, M., Al-Saggaf, Y., Naaji, A., White, J., Jordan, K., Gerstein, J., Umit Yapici, I., Sanga, C., Nleya, P., Sbihi, B., Rocha Lucas, M., Mbarika, V., Reiners, Torsten, Schön, S., Sujo-Montes, L., Santally, M., Häkkinen, P., Al Saif, A., Gegenfurtner, A., Schatz, S., Padilla Vigil, V., Tannahill, C., Padilla Partida, S., Zhang, Z., Charalambous, K., Moreira, A., Coto, M., Laxman, K., Sara Farley, H., Gumbo, M., Simsek, A., Ramganesh, E., Birzina, R., Player-Koro, C., Dumbraveanu, R., Ziphorah, M., Mohamudally, N., Thomas, S., Romero, M., Nirmala, M., Cifuentes, L., Osaily, R., Clemency Omoogun, A., Seferoglu, S., Elçi, A., Edyburn, D., Moudgalya, K., Ebner, M., Bottino, R., Khoo, E., Pedro, L., Buarki, H., Román-Odio, C., Qureshi, I., Ahsan Khan, M., Thornthwaite, C., Kerimkulova, S., Downes, T., Malmi, L., Bardakci, S., Itmazi, J., Rogers, J., Rughooputh, S., Ali Akour, M., Henderson, J., de Freitas, S., Schrader, P., Al Lily, A., Foland, J., Stoloff, D., Gogus, A., Deniz Erguvan, I., Tomé Awshar, M., Tondeur, J., Hammond, M., Venter, I., Jerry, P., Vlachopoulos, D., Oni, A., Liu, Y., Badosek, R., López de la Madrid, M., Mazzoni, E., Lee, H., Kinley, K., Kalz, M., Sambuu, U., Bushnaq, T., Pinkwart, N., Adedokun-Shittu, N., Zander, P., Oliver, K., Pombo, L., Balaban Sali, J., Gregory, S., Tobgay, S., Joy, M., Elen, J., Jwaifell, M., Said, M., Al-Saggaf, Y., Naaji, A., White, J., Jordan, K., Gerstein, J., Umit Yapici, I., Sanga, C., Nleya, P., Sbihi, B., Rocha Lucas, M., Mbarika, V., Reiners, Torsten, Schön, S., Sujo-Montes, L., Santally, M., Häkkinen, P., Al Saif, A., Gegenfurtner, A., Schatz, S., Padilla Vigil, V., Tannahill, C., Padilla Partida, S., Zhang, Z., Charalambous, K., Moreira, A., Coto, M., Laxman, K., Sara Farley, H., Gumbo, M., Simsek, A., Ramganesh, E., Birzina, R., Player-Koro, C., Dumbraveanu, R., Ziphorah, M., Mohamudally, N., Thomas, S., Romero, M., Nirmala, M., Cifuentes, L., Osaily, R., Clemency Omoogun, A., Seferoglu, S., Elçi, A., Edyburn, D., Moudgalya, K., Ebner, M., Bottino, R., Khoo, E., Pedro, L., Buarki, H., Román-Odio, C., Qureshi, I., Ahsan Khan, M., Thornthwaite, C., Kerimkulova, S., Downes, T., Malmi, L., Bardakci, S., Itmazi, J., Rogers, J., Rughooputh, S., Ali Akour, M., Henderson, J., de Freitas, S., and Schrader, P.

Abstract

This article theorizes the functional relationship between the human components (i.e., scholars) and non-human components (i.e., structural configurations) of academic domains. It is organized around the following question: in what ways have scholars formed and been formed by the structural configurations of their academic domain? The article uses as a case study the academic domain of education and technology to examine this question. Its authorship approach is innovative, with a worldwide collection of academics (99 authors) collaborating to address the proposed question based on their reflections on daily social and academic practices. This collaboration followed a three-round process of contributions via email. Analysis of these scholars’ reflective accounts was carried out, and a theoretical proposition was established from this analysis. The proposition is of a mutual (yet not necessarily balanced) power (and therefore political) relationship between the human and non-human constituents of an academic realm, with the two shaping one another. One implication of this proposition is that these non-human elements exist as political ‘actors’, just like their human counterparts, having ‘agency’ – which they exercise over humans. This turns academic domains into political (functional or dysfunctional) ‘battlefields’ wherein both humans and non-humans engage in political activities and actions that form the identity of the academic domain. For more information about the authorship approach, please see Al Lily AEA (2015) A crowd-authoring project on the scholarship of educational technology. Information Development. doi: 10.1177/0266666915622044.

Published
2017

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