Coexistence of the topological state and a two-dimensional electron gas on the surface of Bi2Se3

TL;DR

This paper demonstrates that a two-dimensional electron gas (2DEG) can form on the surface of Bi2Se3 due to band bending, coexisting with topological surface states, which could enable novel physical phenomena and applications.

Contribution

It reveals the coexistence of topological surface states and a 2DEG on Bi2Se3 surfaces caused by band bending, a novel finding in topological insulator research.

Findings

Formation of a 2DEG due to band bending on Bi2Se3 surface

Coexistence of topological surface states and 2DEG

Potential for tunable and superconducting metallic states

Abstract

Topological insulators are a recently discovered class of materials with fascinating properties: While the inside of the solid is insulating, fundamental symmetry considerations require the surfaces to be metallic. The metallic surface states show an unconventional spin texture, electron dynamics and stability. Recently, surfaces with only a single Dirac cone dispersion have received particular attention. These are predicted to play host to a number of novel physical phenomena such as Majorana fermions, magnetic monopoles and unconventional superconductivity. Such effects will mostly occur when the topological surface state lies in close proximity to a magnetic or electric field, a (superconducting) metal, or if the material is in a confined geometry. Here we show that a band bending near to the surface of the topological insulator Bi$_2$Se$_3$ gives rise to the formation of a two-dimensional electron gas (2DEG). The 2DEG, renowned from semiconductor surfaces and interfaces where it forms the basis of the integer and fractional quantum Hall effects, two-dimensional superconductivity, and a plethora of practical applications, coexists with the topological surface state in Bi$_2$Se$_3$. This leads to the unique situation where a topological and a non-topological, easily tunable and potentially superconducting, metallic state are confined to the same region of space.