SFB Colloquium

By Anna Isaeva, Alexander Zeugner, Florian Pielnhofer, Tatiana Menshchikova, Igor Rusinov, Falk Pabst

Almost a decade after the pioneering experimental discovery of topological insulators in HgTe/CdTe quantum wells and in the Bi₂Te₃ family, there exists an entire palette of various topological phases of matter, hosting new quasiparticles and presumably capable of manifesting quantum phenomena under normal conditions. To name a few, symmetry-protected topological phases, topological semimetals (Dirac and Weyl), magnetic topological insulators and superconductors, skyrmions, topological photonic crystals, etc. have been accounted for.

Against this colorful background landscape, our synergetic efforts of chemists and theoreticians (TU Dresden, MPI Stuttgart, IFW Dresden, RWTH Aachen, EPFL, DIPC San-Sebastian (Spain)) pursue a quest for new topological materials amongst layered bulk halides and chalcogenides [1]. The layered structure type allows a relatively flexible exchange and/or chemical modification of the constituting structural fragments – a “chemical” tool to influence the topological properties. Despite the seeming simplicity, this approach has yielded the first WTI Bi₁₄Rh₃I₉ [2], WTI and TCI Bi₂TeI [3] and β-Bi₄I₄, an STI in the proximity of a topological transition [4].

In this talk, the most recent newcomers will be presented. Layered GaGeTe-type structures are an example of covalently functionalized germanene, that undergoes strain-induced topological transition [5]. An extensive family of Bi_xTeHal (Hal = I, Br; x = 2, 3) structures [6, manuscript by Zeugner et al. in preparation] exemplifies how insertion of bismuth-bilayers into the periodic bulk of BiTeHal (Hal = I, Br) steers evolution of topological properties from WTI/TCI to topological semimetals and metals. Prospects of new Dirac semimetals based on PdTe₂ [7] and magnetically ordered compounds will be discussed in conclusion.

References:

[1] A. Isaeva, B. Rasche, M. Ruck. Bismuth-based candidates for topological insulators: Chemistry beyond Bi₂Te₃. Phys. Stat. Solidi RRL, 1–2 (2013), 39.

[2] B. Rasche, A. Isaeva, M. Ruck, S. Borisenko, V. Zabolotnyy, B. Büchner, K. Koepernik, C. Ortix, M. Richter, J. van den Brink. Stacked topological insulator built from bismuth-based graphene sheet analogues. Nature Mater. 12 (2013), 422.

[3] I.P. Rusinov, T.V. Menshchikova, A. Isaeva, S.V. Eremeev, Yu. M. Koroteev, M. G. Vergniory, P. M. Echenique, E.V. Chulkov. Mirror-symmetry protected non-TRIM surface state in the weak topological insulator Bi₂TeI. Sci. Rep. 6 (2016), 20734.

[4] G. Autès, A. Isaeva, L. Moreschini, J. C. Johannsen, A. Pisoni, R. Mori, W. Zhang, T. G. Filatova, A. N. Kuznetsov, L. Forró, W. Van den Broek, Y. Kim, K. Su Kim, A. Lanzara, J. D. Denlinger, E. Rotenberg, A. Bostwick, M. Grioni, O. V. Yazyev. A Novel Quasi-One-Dimensional Topological Insulator in Bismuth Iodide β-Bi₄I₄. Nature Mater. 15 (2016), 154.

[5] F. Pielnhofer, T.V. Menshchikova, I.P. Rusinov, A. Zeugner, I. Yu. Sklyadneva, R. Heid, K.-P. Bohnen, P. Golub, A.I. Baranov, E.V. Chulkov, A. Pfitzner, M. Ruck, A. Isaeva. Designing 3D topological insulators by 2D-Xene (X = Ge, Sn) sheet functionalization in GaGeTe-type structures. J. Mater. Chem. C 5 (2017), 4752.

[6] A. Zeugner, M. Kaiser, P. Schmidt, T.V. Menshchikova, I.P. Rusinov, A.V. Markelov, W. Van den Broek, E.V. Chulkov, T. Doert, M. Ruck, A. Isaeva. Modular design with 2D topological-insulator building blocks: optimized synthesis and crystal growth, crystal and electronic structures of Bi_xTeI (x = 2, 3). Chem. Mater. 29 (2017), 1321.

[7] H.-J. Noh, J. Jeong, E.-J. Cho, K. Kim, B. I. Min, B.-G. Park. Experimental Realization of Type-II Dirac Fermions in a PdTe₂ Superconductor. Phys. Rev. Lett. 119 (2017), 016401.