Realization of a vertical topological p-n junction in epitaxial $\mathrm{Sb_2Te_3 / Bi_2Te_3}$ heterostructures

TL;DR

This paper demonstrates the creation of a vertical topological p-n junction using epitaxial heterostructures of $ ext{Sb}_2 ext{Te}_3$ and $ ext{Bi}_2 ext{Te}_3$, showing tunable chemical potential and potential for exploring exotic quantum states.

Contribution

It provides the first direct experimental evidence of a vertical topological p-n junction in epitaxial heterostructures of two 3D topological insulators, with tunable electronic properties.

Findings

Chemical potential tunable by about 200 meV

Epitaxial heterostructure of $ ext{Sb}_2 ext{Te}_3$ and $ ext{Bi}_2 ext{Te}_3$ realized

Potential to observe topological exciton condensate

Abstract

3D topological insulators are a new state of quantum matter which exhibits both a bulk band structure with an insulating energy gap as well as metallic spin-polarized Dirac fermion states when interfaced with a topologically trivial material. There have been various attempts to tune the Dirac point to a desired energetic position for exploring its unusual quantum properties. Here we show a direct experimental proof by angle-resolved photoemission of the realization of a vertical topological p-n junction made of a heterostructure of two different binary 3D TI materials $\mathrm{Bi_2Te_3}$ and $\mathrm{Sb_2Te_3}$ epitaxially grown on Si(111). We demonstrate that the chemical potential is tunable by about 200 meV when decreasing the upper $\mathrm{Sb_2Te_3}$ layer thickness from 25 to 6 quintuple layers without applying any external bias. These results make it realistic to observe the topological exciton condensate and pave the way of exploring other exotic quantum phenomena in the near future.