- Gunther Springholz: Topological Crystalline Insulator Heterostructures
- 7. 2. 2018, 13:00
- lecture room F2, first floor Ke Karlovu 5
- more information
Abstract:
Topological crystalline insulators (TCI) are an alternative class of topological insulators with many valley band structure and topological surface states protected by crystal mirror symmetries instead of time reversal symmetry [1] as in the Bi-chalcogenides. The most prominent example for TCIs are the Sn-based IV-VI semiconductors such as Pb1-xSnxTe and Pb1-xSnxSe in which an inversion of the conduction and valence band occurs when the Sn content exceeds a certain critical value [2-4]. A particular interesting feature is that the electronic band structure and thus the topological properties can be tuned by external means such as strain, temperature, as well as by magnetic and electric fields. Up to now, most investigations of the topological surface state have been performed on the (100) cleavage surfaces of bulk single crystals but for practical applications obviously thin film heterostructures are required.
In this presentation, I will describe our recent progress on molecular beam epitaxy of IV-VI TCI heterostructures grown on various different substrates in different orientations. The electronic structure and band topology were investigated by angle resolved photoemission (ARPES) at synchrotrons as well as magneto-transport [5] and magneto-optical Landau level spectroscopy [6]. I will present selected results with particular focus on the effect of extrinsic doping [7,8], strain and band structure engineering, as well as quantum size effects in heterostructures.
[1] Liang Fu, Phys. Rev. Lett. 106, 106802 (2011) ; and T.H. Hsieh et al., Nature Commun. 3, 982 (2012).
[2] S.-Y. Xu et al., Nature Commun. 3, 1192 (2012).
[3] Y. Tanaka et al., Nature Phys. 8, 800 (2012).
[4] P. Dziawa et al., Nature Materials 11, 1023 (2012).
[5] B. A. Assaf et al., Phys. Rev. Lett. 119, 106602 (2017).
[6]B. A. Assaf et al, npj Quantum Mater. 2, 26 (2017).
[7] V. V. Volobuev et al., Adv. Mater. 29, 1604185 (2017).
[8] P. Mandal et al., Nature Commun., in print.