Tailoring the band structure of thin films by strain and by the growth of artificial heterostructures

• Applicant: Dr. David Flötotto
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2016 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 324999712

The electronic band structure of a material determines its electronic, optical, magnetic and catalytic properties and thus a precise adjustment of the band structure is of fundamental importance for a wide range of applications. This requires a comprehensive understanding of the correlation of the band structure with the atomic constitution. Two possible ways to tailor the band structure of thin films are the growth of artificial heterostructures and the imposing of a mechanical strain. In particular, strain is considered as a powerful tool, since, within the elastic regime of the material, it bears the potential for a reversible in-situ engineering of the electronic band structure and thus the functional properties of the material.By performing angle-resolved photoemission spectroscopy during uniaxial tensile testing of ultrathin films, we want to establish the effect of strain on the band structure of topological insulators, topological crystalline insulators and transition metal dichalcogenides. In combination with a detained characterization of the microstructure and the stress state of the thin films, this will enable a systematic quantification of the effect of strain and of breaking the crystal symmetry on the band structure and pave the way to use strain as an in-situ tool for tailoring the band structure. Furthermore, we plan to investigate the proximity effect between a superconductor and a topological insulator. By performing angle-resolved photoemission spectroscopy, we will establish the proximity-induced superconductivity in the topological surface state and the bulk bands as functions of the topological insulator film thickness as well as the temperature, shedding light on the mechanism and the decisive factors for the proximity-induced superconductivity.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Tai-Chang Chiang