Observation of a Smoothly Tunable Dirac Point in $Ge(Bi_{x}Sb_{1-x})_{2}Te_{4}$

TL;DR

This paper demonstrates a continuously tunable Dirac point in the topological material Ge(Bi_xSb_{1-x})_2Te_4, with potential implications for topological spintronics, by combining FT-STS and ARPES measurements across different compositions.

Contribution

It reports the first observation of a smoothly tunable, isolated Dirac point crossing the Fermi level in a topological material through chemical substitution.

Findings

Dirac point shifts linearly with Bi/Sb ratio

Crosses Fermi energy near x=0.7

Potential for topological spintronics applications

Abstract

State-of-the-art topological devices require the use topological surface states to drive electronic transport. In this study, we examine a tunable topological system, $Ge(Bi_{x}Sb_{1-x})_{2}Te_{4}$, for a range of 'x' values from 0 to 1, using a combination of Fourier Transform Scanning Tunneling Spectroscopy (FT-STS) and Angle-Resolved Photoemission Spectroscopy (ARPES). Our results show that the Dirac point shifts linearly with 'x', crossing the Fermi energy near x = 0.7. This novel observation of a smoothly tunable, isolated Dirac point crossing through the topological transport regime and having strong linear dependence with substitution can be critical for future topological spintronics applications.