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

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, Ge(BixSb1-x)2Te4, 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.