Trigger of the ubiquitous surface band bending in 3D topological insulators

Abstract

The main scientific activity in the field of topological insulators (TIs) consists of determining their electronic structure by means of magneto-transport and electron spectroscopy with a view to devices based on topological transport. There is however a caveat in this approach. There are systematic experimental discrepancies on the electronic structure of the most pristine surfaces of TI single crystals as determined by Shubnikov de Haas (SdH) oscillations and by Angle Resolved PhotoElectron Spectroscopy (ARPES). We identify intense ultraviolet illumination -that is inherent to an ARPES experiment- as the source for these experimental differences. We explicitly show that illumination is the key parameter, or in other words the trigger, for energetic shifts of electronic bands near the surface of a TI crystal. This finding revisits the common belief that surface decoration is the principal cause of surface band bending and explains why band bending is not a prime issue in the illumination-free magneto-transport studies. Our study further clarifies the role of illumination on the electronic band structure of TIs by revealing its dual effect: downward band bending on very small timescales followed by band flattening at large timescales. Our results therefore allow us to present and predict the complete evolution of the band structure of TIs in a typical ARPES experiment. By virtue of our findings, we pinpoint two alternatives of how to approach flat band conditions by means of photon-based techniques and we suggest a microscopic mechanism that can explain the underlying phenomena.

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• Sample-dependent Dirac point gap in MnBi${}_2$Te${}_4$ and its response to the applied surface charge: a combined photoemission and ab initio study
• Light-Tunable Surface State and Hybridization Gap in Magnetic Topological Insulator MnBi${}_8$Te${}_{13}$
• Landau level spectroscopy of PbSnSe topological crystalline insulator
• Spatial Control of Charge Doping in n-Type Topological Insulators
• Observability of superconductivity in Sr-doped Bi2Se3 at the surface using scanning tunneling microscope
• Characterizing the chemical potential disorder in the topological insulator (Bi${}_{1-x}$Sb${}_x$)${}_2$Te${}_3$ thin films
• High and Magnetic-field-dependent Surface Carriers Mobility in 3D Topological Insulators without Bulk States