Tuning the Dirac point to the Fermi level in the ternary topological insulator (Bi$_{1-x}$Sb$_{x}$)$_{2}$Te$_{3}$

TL;DR

This study demonstrates that (Bi$_{1-x}$Sb$_{x}$)$_{2}$Te$_{3}$ thin films can be tuned so that the Dirac point aligns closely with the Fermi level, which is crucial for stabilizing Majorana excitations in topological superconductors.

Contribution

The paper shows that by using molecular beam epitaxy, the Dirac point in (Bi$_{1-x}$Sb$_{x}$)$_{2}$Te$_{3}$ can be tuned within 10 meV of the Fermi level, with no bulk bands crossing it.

Findings

Dirac point within 10 meV of Fermi level

No bulk bands intersect the Fermi level

Preparation method achieves precise Dirac point tuning

Abstract

In order to stabilize Majorana excitations within vortices of proximity induced topological superconductors, it is mandatory that the Dirac point matches the Fermi level rather exactly, such that the conventionally confined states within the vortex are well separated from the Majorana-type excitation. Here, we show by angle resolved photoelectron spectroscopy that (Bi$_{1-x}$Sb$_{x}$)$_{2}$Te$_{3}$ thin films with $x=0.94$ prepared by molecular beam epitaxy and transferred in ultrahigh vacuum from the molecular beam epitaxy system to the photoemission setup matches this condition. The Dirac point is within 10 meV around the Fermi level and we do not observe any bulk bands intersecting the Fermi level.