Observation of a smoothly tunable Dirac point in Ge(BixSb1−x)2Te4

Abstract

State-of-the-art topological devices require the use of topologically protected surface states to drive electronic transport. In this paper, we examine a tunable topological system, $\mathrm{Ge}{({\mathrm{Bi}}_{x}{\mathrm{Sb}}_{1\text{\ensuremath{-}}x})}_{2}{\mathrm{Te}}_{4}$, for a range of $x$ values from 0 to 1, using a combination of Fourier transform scanning tunneling spectroscopy and angle-resolved photoemission spectroscopy. Our results show that the Dirac point shifts linearly with $x$, crossing the Fermi energy near $x=0.7$. This 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.